    LINGO

               Table of Contents

Preface ....................................................................................................... ix

Part I: Lingo Basics

Chapter 1--How Lingo Thinks ......................................................... 3

     So You're Too Busy to Learn Lingo ...................................................... 3
     Lingo Scripting Basics ............................................................................ 5
     Variables and Properties ...................................................................... 21
     Lingo's Skeletal Structure ..................................................................... 38
     Conditional Execution .......................................................................... 43
     Parameters and Arguments .................................................................. 55

Chapter 2--Events, Messages, and Scripts ................................ 69

     Events and Messages ............................................................................ 69
     Lingo Script Types ................................................................................ 77
     Trapping Events with Scripts ............................................................... 94
     Message Processing Order ................................................................. 103

Chapter 3--Lingo Coding and Debugging Tips .................... 113

     Lingo Coding Tips .............................................................................. 113
     Zen and the Art of Debugging .......................................................... 125
     The Lingo Debugger .......................................................................... 129
     A Simple Sample Debugging Session ................................................ 143
     Lingo Debugging Commands ............................................................ 147

                                                     v
Chapter 4--Lingo Internals .......................................................... 150

     Lingo Internals .................................................................................... 150

Part II: Lingo Data Types and Expressions

Chapter 5--Data Types and Expressions ................................ 161

     Data Types and Variable Types ......................................................... 161
     Operators ............................................................................................ 173

Chapter 6--Lists ................................................................................ 180

     List Basics ............................................................................................ 180
     Lingo List Commands ......................................................................... 188
     Commands by List Type .................................................................... 202
     List Utilities .......................................................................................... 208
     Other Lingo Commands That Use Lists ............................................. 212

Chapter 7--Strings ........................................................................... 215

     Strings and Chunk Expressions ......................................................... 215

Chapter 8--Math (and Gambling) ............................................ 227

     Arithmetic Operators .......................................................................... 227
     Math Functions ................................................................................... 231
     Number Systems and Formats ........................................................... 239

Part III: Lingo Events

Chapter 9--Mouse Events .............................................................. 251

     Mouse Events ...................................................................................... 251
     Mouse Properties ................................................................................ 266
     Mouse Tasks ....................................................................................... 268

Chapter 10--Keyboard Events ..................................................... 275

     Keyboard Events ................................................................................. 275
     Keyboard Properties ........................................................................... 278
     Filtering Keyboard Input .................................................................... 288
     Keyboard Tasks .................................................................................. 295

vi
Chapter 11--Timers and Dates ................................................... 301

     Timers and Delays .............................................................................. 301
     Time Units ........................................................................................... 307
     Date and Time Functions ................................................................... 312
     Timing Utilities ................................................................................... 315

Part IV: Applied Lingo

Chapter 12--Behaviors and Parent Scripts ............................ 321

     What Is a Behavior? ............................................................................ 321
     Objects of Mystery .............................................................................. 326
     Behaviors versus Other Script Types ................................................ 338
     Behavior and Parent Script Lingo ...................................................... 345

Chapter 13--Lingo Xtras and XObjects ................................... 350

     Xtras .................................................................................................... 350
     Lingo Scripting Xtras .......................................................................... 352
     Writing Your Own Xtras .................................................................... 363

Chapter 14--External Files ........................................................... 365

     External Files ...................................................................................... 365
     File Paths ............................................................................................. 368
     FileIO .................................................................................................. 376
     External Applications ......................................................................... 388

Chapter 15--The MUI Dialog Xtra ............................................ 391

     MUI Alert Dialogs ............................................................................... 391
     Custom MUI Dialogs .......................................................................... 393

Part V: Lingo Command Reference

Chapter 16--Enumerated Values ............................................... 397

Chapter 17--Changed, Undocumented, and
    Misdocumented Lingo .............................................................. 424

     Underdocumented Utilities and Lingo .............................................. 424

                                                                                                         vii
Chapter 18--Lingo Keyword and Command Summary .. 440
Chapter 19--The Lingo Symbol Table ...................................... 521

     Why Do I Care? .................................................................................. 521

Part VI: Appendixes

Appendix A--ASCII Codes and Key Codes .............................. 529
Appendix B--Changes in D6 Through D6.5 .......................... 537
Appendix C--Case-Sensitivity, Sort Order,

    Diacritical Marks, and Space-Sensitivity ......................... 553
Appendix D--The DIRECTOR.INI and LINGO.INI Files ..... 561
Appendix E--Error Messages and Error Codes ..................... 568
Glossary ................................................................................................ 587
Index ...................................................................................................... 593

viii
         Preface

                      Preface

About This Book

You are holding in your hands one half of Bruce's Brain in a Book. The other half
of my brain is in the companion book, Director in a Nutshell. These books are the
distillation of years of real-life experience with countless Director projects plus
many hours spent researching and testing Director 6's and 6.5's new features.
While they can be used separately, they are ideally used as a single two-volume
reference, which can be purchased together for less than most single Director
books.

            Lingo in a Nutshell focuses on the abstract concepts in Lingo--vari-
            ables, scripts, Behaviors, objects, mouse and keyboard events, timers,
            math, lists, strings, and file I/O. Director in a Nutshell focuses on the
            concrete aspects of Director--the Cast, the Score, Projectors, MIAWs,
            media (graphics, sound, digital video, text), Director's windows, GUI
            components (buttons, cursors, menus) and Shockwave.

If you already know a lot about Director or have been disappointed by the
existing documentation, these are the books you've been waiting for. They address
many of the errors and omissions in Macromedia's documentation and in many
third-party books. There is no fluff or filler here, so you'll miss a lot if you skim.
We are both busy, so let's get on with it.

What Are These Books and Who Are They for?

Director in a Nutshell and Lingo in a Nutshell are desktop quick references for
Director and Lingo developers who are familiar with Director's basic operation and
need to create, debug, and optimize cross-platform Director and Shockwave

                                                     ix
About This Book

        projects. These books are concise, detailed, respectful of the reader's intelligence,
        and organized by topic to allow quick access to thorough coverage of all relevant
        information.

        Because Lingo and Director are inextricably linked, I have kept all information on
        a single topic within a single chapter rather than breaking it along the traditional
        Director versus Lingo lines (with the exception of the Using Xtras and Lingo Xtras
        and XObjects chapters). Don't be fooled by the titles of the books; both include a
        lot of Lingo, and they should be read in parallel.

        Director in a Nutshell should not be confused with the third-party books that
        merely rehash the manuals, nor should it be considered an introductory book. It is
        exceptionally valuable for non-Lingo users but also covers Lingo related to those
        aspects of Director mentioned previously. Lingo in a Nutshell covers both the very
        basics of Lingo and its most advanced features. It is for both new and experi-
        enced Lingo programmers, which may sound impossible but isn't. Each book
        covers both Windows and the Macintosh.

        To describe them as "beginner," "intermediate," or "advanced" would be
        misleading because they cover both the very basic foundation of Director and its
        very advanced usage. Strictly as a comparison to other books on the market, you
        should consider their coverage extremely advanced, but the text itself is accessible
        to Director users of all levels. Lingo in a Nutshell allows Director users to take full
        advantage of Lingo's power, and Director in a Nutshell helps users of all levels
        deal confidently with the spectrum of Director's media types and features.

      What These Books Are Not

        These books are not a rehash of the Director manuals or Help system but rather a
        complement to them; as such, they are unlike any other books on the market.

        These books are not a celebration of Director as multimedia Nirvana. They are for
        people who know that Director has many quirks and some bugs and want to
        know how to work around them quickly and effectively.

        These books are not courses in graphic design, project management, Photoshop,
        HTML, or JavaScript. They will, however, help you to integrate your existing skills
        and external content into Director's framework.

        These books are not a Director tutorial; I assume that you are familiar with the
        basics of Director's Cast, Score, Stage, and menus. They are not for people who
        need hand-holding. They are for people who can apply general concepts to their
        specific problem and want to do so rapidly.

        These books are not perfect--errors are inevitable--so use them as a guide, not
        the gospel. Although these books cannot anticipate all circumstances, they do
        provide the tools for you to confidently solve your specific problems, even in the
        face of erroneous or incomplete information.

        Last, these books are not a static lecture. They are an ongoing conversation between
        you, the reader, and me, the author. Feedback from many customers, clients, and
        friends has already shaped their content. I have packed them with facts, but I also
        provide the tools to allow you to understand and debug any situation. Let us see if

        x Preface
                                                                                                            Preface

we can solve some problems in Director and learn something about ourselves along
the way.

Lingo in a Nutshell

Lingo in a Nutshell covers the abstract aspects of Lingo that exist apart from its
control over media elements, the Cast, and the Score. This book covers the spec-
trum from Lingo basics to advanced scripting with Lists, Behaviors, and Xtras. It is
divided into five major sections.

Part I, Lingo Basics
      Chapter 1, How Lingo Thinks, defines the Lingo language and its syntax
      including handlers, variables, and Lingo control structures. Refer also to
      Chapter 1, How Director Thinks in Director in a Nutshell.

      Chapter 2, Events, Messages, and Scripts, explains where, when, and how to
      use various types of scripts to detect user and system events. It covers the
      new event and message passing in Director 6, including details on trapping
      events with Behaviors.

      Chapter 3, Lingo Coding and Debugging Tips, helps you plan your Lingo and
      covers the Debugger, Message window, and Lingo error messages. See also
      Appendix E, Error Messages and Error Codes.

      Chapter 4, Lingo Internals, is designed for experienced programmers and
      compares Lingo's syntax, commands, and structure to those of other
      languages. Refer also to the downloadable Chapter 20, Lingo for C
      Programmers.

Part II, Lingo Data Types and Expressions
      Chapter 5, Data Types and Expressions, covers Lingo data types, implicit and
      explicit type conversion and coercion, type checking, logical expressions,
      comparison operators, and string operators.

      Chapter 6, Lists, is a life-saving chapter covering the commands for linear lists,
      property lists, points, and rectangles in well-organized tables. It contains
      numerous examples including randomized and non-repeating lists.

      Chapter 7, Strings, covers string expressions, concatenation, parsing, and
      manipulation, and chunk expressions (characters, words, items, lines, and
      fields). See also Chapter 12, Text and Fields, in Director in a Nutshell.

      Chapter 8, Math (and Gambling), covers arithmetic operators, math func-
      tions, exponentiation, geometry and trig functions, rounding and truncation,
      and random numbers.

Part III, Lingo Events
      Chapter 9, Mouse Events, covers responding to mouse clicks and cursor move-
      ment, including how to make buttons with rollover and highlight states.

      Chapter 10, Keyboard Events, covers responding to keyboard input and trap-
      ping various key combinations (including modifier keys, function keys, arrow
      keys, and the numeric keypad).

      Chapter 11, Timers and Dates, covers timers, time-outs, dates, times, and unit
      conversion.

                                                                                             Preface xi
Lingo in a Nutshell

        Part IV, Applied Lingo
              Chapter 12, Behaviors and Parent Scripts, helps you make the most of Behav-
              iors and other object-oriented scripting techniques.
              Chapter 13, Lingo Xtras and XObjects, covers using Xtras and XObjects to
              extend Lingo's scripting language. See also Chapter 10, Using Xtras, in
              Director in a Nutshell.
              Chapter 14, External Files, covers the FileIO Xtra for reading and writing files
              from within Director. It also covers commands that work with external
              Director-related files and non-Director documents and applications.
              Chapter 15, The MUI Dialog Xtra, covers using the MUI Xtra to create basic
              Alert dialogs. Refer also to the downloadable Chapter 21, Custom MUI Dialogs,
              which provides painstaking detail on creating custom dialogs with the MUI
              Xtra.

        Part V, Lingo Command Reference
              Chapter 16, Enumerated Values, lists all the Lingo commands that accept or
              return numeric codes, symbols, or strings that indicate particular values,
              including transitions, ink effects, palettes, cursors, and window types.
              Chapter 17, Changed, Undocumented, and Misdocumented Lingo, covers
              Lingo commands that are undocumented or misdocumented or behave differ-
              ently in Director 6 than in prior versions of Director.
              Chapter 18, Lingo Keyword and Command Summary, is a complete list of
              every command, function, symbol, and string recognized by Lingo, including
              a syntax example.
              Chapter 19, The Lingo Symbol Table, explains the inner workings of the
              hidden Symbol Table and symbols in general. Refer also to the downloadable
              Chapter 22, Symbol Table Archaeology, for additional details.

        Part VI, Appendixes
              Appendix A, ASCII Codes and Key Codes
              Appendix B, Changes in D6 Through D6.5
              Appendix C, Case-Sensitivity, Sort Order, Diacritical Marks, and Space-
              Sensitivity
              Appendix D, The DIRECTOR.INI and LINGO.INI Files
              Appendix E, Error Messages and Error Codes
              Glossary

        The economics of print publishing precluded me from including everything in this
        book. The good news is that the material (plus many more examples) is available
        online in PDF (Acrobat) format (see http://www.zeusprod.com/nutshell).

        Online Bonus Chapters:
              Chapter 20, Lingo for C Programmers, is designed for experienced program-
              mers and compares Lingo's syntax, commands, and structure to C. It picks up
              where Chapter 4, leaves off.

        xii Preface
                                                                                                            Preface

      Chapter 21, Custom MUI Dialogs, covers the excruciating details of using the
      MUI Xtra to create custom dialog boxes. It expands on Chapter 15, which
      covers only the MUI Xtra's Alert() method.
      Chapter 22, Symbol Table Archaeology, covers the history and hidden secrets
      of the Lingo Symbol Table and complements Chapter 19.
The companion volume, Director in a Nutshell, covers content development and
delivery in Director. It also covers media and user interface elements and the
Lingo to control them. Refer to the Preface in Director in a Nutshell for details.

Conventions Used in This Book

Typographical Conventions

 Lingo keywords (functions, commands, and property names) are shown in
      italics except in tables where they are italicized only when necessary to dis-
      tinguish them from the surrounding text. Italics in tables usually indicate
      replaceable values.

 Arguments, user-specified, and replaceable items are shown in ital-
      ics and should be replaced by real values when used in your code.

 New terms are shown in italics and are often introduced by merely using
      them in context. Refer to the Glossary for details.

 Menu commands are shown as MenuNameMenuItem.
 Options in dialog boxes, such as the Tab to Next Field checkbox, are shown

      in italics.
 Constants, such as TRUE, FALSE, and RETURN, are shown in Courier.
 #symbols are preceded by the # character and shown in Courier.
 Optional items are specified with curly braces ({}) instead of the traditional

      square braces ([]) which Lingo uses for lists. For example:
      go {to} {frame} whichFrame
      means that the following all are equivalent:
      go whichFrame
      go to whichFrame
      go to frame whichFrame
      go frame whichFrame
 Allowed values for a property are separated by a "|". The following indicates
      that the alignment of member property can be set to "left," "right," or "center":
      set the alignment of member 1 = "left" | "right" | "center"

Grammatical and Stylistic Conventions

 Most Lingo properties start with the word the, which can lead to sentences
      such as "The the member of sprite property can be changed at runtime." I often
      omit the keyword the preceding properties to make sentences or tables more
      readable, but you should include the the in your Lingo code.

                                                                                           Preface xiii
Conventions Used in This Book

 Lingo event handlers all begin with the word on, such as on mouseUp. I often
      omit the word on when discussing events, messages, and handlers or in tables
      where the meaning is implied.

 Be aware that some Director keywords are used in multiple contexts such as
      the on mouseUp event handler and the the mouseUp system property. The
      intended usage is discernible from context, or stated explicitly in ambiguous
      circumstances.

 I use terminology fairly loosely, as is typical among Lingo developers. For
      example, a "mouseUp script" is technically "an on mouseUp handler within a
      script." The meaning should be clear from the context.

 I capitalize the names of Director entities, such as the Score, the Stage, the
      Cast, and the Message window. I don't capitalize general terms that refer to
      classes of items, such as sprite scripts.

 Most handler names used in the examples are arbitrary, although handlers
      such as on mouseUp that trap built-in events must be named as shown. I use
      variable names like myThing or whichSprite to indicate items for which you
      should substitute your own values. When in doubt, consult Table 18-1, "Lingo
      Command and Keyword Summary.

 I use few segues and assume you will reread the material until it makes sense.
      As with a Dal painting, you must revisit the text periodically to discover
      details that you missed the first time.

Examples

 Example code is shown monospaced and set off in its own paragraph. If a
      code fragment is shown, especially using the put command, it is implicit that
      you should type the example in the Message window to see the result. Any
      text following "--" is the output from Director or a comment from me:

set x = 5    -- Set the variable x to 5
put x        -- Display the value of x
-- 5

 Long lines of Lingo code are continued on the next line using the Lingo con-
      tinuation character ([LC]) as shown here. This character is created using Opt-
      Return or Option-L (Macintosh) or Alt-Enter (Windows).

set the member of sprite (the currentSpriteNum) = 
     member "Hilighted Button"

 If you have trouble with an example, check for lines that may have been erro-
      neously split without the Lingo continuation character (). Remember to use
      parentheses when calling any function that returns a value. Otherwise you'll
      either see no result or receive an error.

rollover                       -- wrong
rollover()                     -- wrong
put rollover                   -- wrong
put rollover()                 -- correct

xiv Preface
                                                                                                            Preface

 I sometimes use the single-line form of the if...then statement in an example
      for brevity. You should use multiline if...then statements in your code. See
      Chapter 1 for details on the if statement.

        -- This will usually work
        if (x > 5) then put "It's True!"
        -- But this is more reliable
        if (x > 5) then

              put "It's True!"
        end if

 If a handler is shown in an example, it is implied that the handler has been
      entered into the appropriate type of script. Generally, mouse event handlers
      such as mouseUp belong in sprite scripts; frame events handlers such as exit-
      Frame belong in frame scripts; and custom utilities belong in movie scripts. I
      often show a handler followed by an example of its use. Type the handler
      into an appropriate script, and then test it from the Message window. If I
      don't show a test in the Message window, either the handler does not output
      a visible result, or it is assumed that you will test it yourself.

        -- This goes in a script, in this case a movie script
        on customHandler

            put "Hello Sailor!"
        end customHandler

        -- This is a test in the Message window
        customHandler
        -- "Hello Sailor"

 The output shown may vary inconsequentially from the results you would see
      based on your system setup. Most notably, the number of decimal places out-
      put for floating-point values depends on your setting for the floatPrecision
      property.

 If the output of a handler is extremely long, the results will not be shown in
      their entirety or may not be shown at all.

 The examples are demonstrative and not necessarily robust, and they assume
      that you provide valid inputs when applicable. It is good practice to include
      type checking and error checking in your actual Lingo code, as described in
      Chapters 1 and 3. I often omit such checking to keep examples shorter and to
      focus on the main issue at hand.

 Some examples, particularly the tests performed from the Message window,
      are code fragments and won't work without help from the studio audience.
      You should ensure that any variables required by the examples (particularly
      lists) have been initialized with meaningful values, although such initializa-
      tion is not shown. For example:

      put count (myList)
      The previous code fragment assumes that you have previously set a valid
      value for myList, such as:

      set myList = [1, 7, 5, 9]

 Some examples allude to field cast members, such as:

                                                                                             Preface xv
New Features in Director 6 and 6.5

                set the text of field "Memory" = string(the freeBlock)

              It is implied that you should create a field cast member of the specified name
              in order for the example to work.

         Screen shots may not match your platform's graphical user interface exactly.

         I present a simplified view of the universe whenever my assumptions are
              overwhelmingly likely to be valid. You can intentionally confuse Director by
              setting bizarre values for a property or performing malicious operations, such
              as deleting elements from a rect structure, but you do so at your own risk. I
              cover situations where errors might occur accidentally, but you should assume
              that all statements presented as fact are prefaced by, "Assuming you are not
              trying to screw with Director just for fun..." When they are likely to be relevant,
              I state my assumptions clearly.

         The myriad ways to perform a given task are shown when that task is the
              main topic of discussion but not if it is peripheral to the subject at hand.
              When it is incidental, I may show the most expedient or clearest method
              rather than the suggested method.

         Examples are usually self-contained, but they may rely on custom handlers
              shown nearby. If an example builds on previous examples or material cross-
              referenced in another chapter, it is assumed that the relevant handlers have
              been entered in an appropriate script (usually a movie script).

         What rightly belongs in one table sometimes is broken into two or three due
              to space constraints. Similar information may be organized in different ways in
              multiple tables to help you find what you want, especially in Chapter 6. The
              first column of each table contains the table's "key item" for which full details
              are provided. Subservient items, for which the table may not contain com-
              plete information, are relegated to other columns. For example, if a function is
              listed in the "See Also" column of a table, complete details on that command
              can be found in surrounding prose or other tables.

        Refer to the Glossary for a complete list of definitions.

     New Features in Director 6 and 6.5

        Score, Sprites, Auto-Puppeting, and Paths
              Director's new Score is radically different and includes a Sprite Toolbar and
              customizable views. Sprites receive several new messages (beginSprite,
              endSprite, mouseEnter, mouseLeave, etc.), allowing them to be managed much
              more easily. Refer to Chapter 3, The Score and Animation, in Director in a
              Nutshell and to Chapter 2 in Lingo in a Nutshell.

        Help and Manuals
              The new Help system includes a lot of information that is not in the manuals,
              plus many useful Show Me demonstration movies. Choose Show Me from the
              Help menu or from the Help Contents window for demonstrations of many of
              Director's new features.

        New Behaviors, Messages, Cue Points, and Lingo
              Behaviors allow you to easily add multiple scripts to a sprite. Director's
              message passing has been radically revised, and there are many new

        xvi Preface
                                                                                                            Preface

      messages, including rollover events and error trapping. Refer to Chapter 2, 9,
      and 12. Director now supports cue points for synchronizing sounds with
      animation in the Score (see Chapter 15, Sound and Cue Points, in Director in
      a Nutshell).
Shockwave and Internet Improvements
      Shockwave and Director now support streaming playback of Internet-based
      content. Many Director commands support linking to a URL, and linked cast
      libraries or streaming Shockwave audio can reside on the Internet. New
      commands (frameReady, mediaReady, netDone, etc.) support asynchronous
      operations in Director via the NetLingo Xtra. Refer to Chapter 11, Shockwave
      and the Internet, in Director in a Nutshell.
      Shockwave Audio is now integrated with Director. Local sounds can be
      compressed as well as those on the Internet. See Chapter 15 in Director in a
      Nutshell. Shockwave-style movie compression is also available to make your
      local Director project use less disk space.
New Media Formats and Application Integration
      Director 6.0 supports many new media formats.

            Using external media (including sounds) at runtime requires the MIX
            Services Xtra plus the support Xtra for that particular file type, such
            as Sound Import Export.

      Refer to Chapter 4, CastLibs, Cast Members and Sprites, and Chapter 10, Using
      Xtras, in Director in a Nutshell for details on file import types and the
      required Xtras.
New Features in Director 6.5
      Director 6.5 is the same as version 6.0.2 with the addition of many Xtras. See
      http://www.macromedia.com/software/director/productinfo/newfeatures/ and
      refer to Appendix B, Changes in D6 Through D6.5. Refer also to Director in
      a Nutshell, especially to Appendix B, New Features in Director 6.5, and
      Chapter 16, Digital Video, which covers QuickTime 3.

Director Resources

The best thing about Director is the extended community of developers that you
can torment for assistance. This book notwithstanding, Director is largely undocu-
mented. Visit Macromedia's web site frequently, and plug into the broader Director
community via mailing lists and newsgroups.

Director in a Nutshell and Lingo in a Nutshell

O'Reilly and Associates
      http://www.oreilly.com/catalog/directnut/
      http://www.oreilly.com/catalog/lingonut/

                                                                                           Preface xvii
Director Resources

        Home page for both books
              http://www.zeusprod.com/nutshell

        Download example code
              http://www.zeusprod.com/nutshell/examples.html

        Downloadable bonus chapters (PDF format)
              http://www.zeusprod.com/nutshell/chapters.html

        Links page (all URLs in this book are available by chapter/topic)
              http://www.zeusprod.com/nutshell/links.html

        Web Review--All things browser and web related
              http://www.webreview.com/

      Macromedia

        Macromedia home page and mirror sites
              http://www.macromedia.com
              http://www-euro.macromedia.com
              http://www-asia.macromedia.com

        Director 6.5 update
              http://www.macromedia.com/software/director/productinfo/newfeatures/
              http://www.macromedia.com/software/director/upgrade/

        Director Developers Center (searchable database of Tech Notes and tips)
              http://www.macromedia.com/support/director/
              http://www.macromedia.com/support/search/
              http://www.macromedia.com/support/director/how/subjects/

        Shockwave Developer Center
              http://www.macromedia.com/shockwave/
              http://www.macromedia.com/support/director/how/shock/

        Dynamic HTML and Shockwave browser scripting
              http://www.dhtmlzone.com/swdhtml/index.html

        Director-related newsgroups
              http://www.macromedia.com/support/director/interact/newsgroups/
              news://forums.macromedia.com/macromedia.plug-ins
              news://forums.macromedia.com/macromedia.director.basics
              news://forums.macromedia.com/macromedia.director.lingo

        Priority Access (fee-based) technical support
              http://www.macromedia.com/support/techsupport.html
              http://www.macromedia.com/support/director/suprog/

        Beta program
              http://www.macromedia.com/support/program/beta.html

        Director feature suggestions
              mailto:wish-director@macromedia.com

        xviii Preface
                                                                                                            Preface

Phone support
      MacroFacts (fax information) 1-800-449-3329 or 1-415-863-4409
      Technical Support 1-415-252-9080
      Main Operator: 1-415-252-2000

User groups
      http://www.macromedia.com/support/programs/usergroups/worldwide.html

Developer Locator (find a Director or Lingo developer in your area)
      http://www.macromedia.com/support/developer_locator/

Online services
      CompuServe: Go Macromedia
      AOL: The Macromedia forum on AOL no longer exists.

Macromedia User Conference (UCON), May 2527 1999, in San Francisco, CA
      (There will be no UCON in the fall of 1998.)
      http://www.macromedia.com/events/ucon99/

Web Sites and Xtras

Zeus Productions (my company) technical notes and Xtras
      http://www.zeusprod.com

UpdateStage--monthly technical articles and the Director Quirk List and Xtras
      http://www.updatestage.com
      ftp://ftp.shore.net/members/update/

Director Online Users Group (DOUG)--articles, interviews, reviews
      http://www.director-online.com

Maricopa Director Web--the mothership of Director information
      http://www.mcli.dist.maricopa.edu/director/tips.html
      ftp://ftp.maricopa.edu/pub/mcli/director

Lingo Behavior Database (example Behaviors) maintained by Renfield Kuroda
      http://www.behaviors.com/lbd/

Peter Small's Avatars and Lingo Sourcery (far-out stuff)
      http://avatarnets.com

Links to additional third-party web sites
      http://www.mcli.dist.maricopa.edu/director/net.html
      http://www.macromedia.com/support/director/ts/documents/tn3104-dirweb-
      sites.html

Third-Party Xtras
      http://www.macromedia.com/software/xtras/director

FMA Online (Links to many Xtra developers)
      http://www.fmaonline.com

Xtras developer programs
      http://www.macromedia.com/support/program/xtrasdev.html
      http://www.macromedia.com/support/xtras.html

                                                                                            Preface xix
Dedication

        QuickTime
              http://quicktime.apple.com/

        Microsoft
              http://support.microsoft.com/

      Mailing Lists

        If you have the bandwidth, these mailing lists are often useful resources for
        Director, Shockwave, Xtras, and Lingo questions (see the Macromedia news-
        groups). These mailing lists generate a lot of mail. Subscribe using DIGEST mode
        to avoid hundreds of separate e-mails each day.
        DIRECT-L (Director and Lingo)

              Archives: http://www.mcli.dist.maricopa.edu/director/digest/index.html
              MailList: http://www.mcli.dist.maricopa.edu/director/direct-l/index.html
              Send the following in the body of an e-mail to listserv@uafsysb.uark.edu:
                SUBSCRIBE DIRECT-L yourFirstName yourLastName
                SET DIRECT-L DIGEST
        Lingo-L (Lingo)
              http://www.penworks.com/LUJ/lingo-l.cgi
        ShockeR (Shockwave)
              Archive: http://ww2.narrative.com/shocker.nsf
              MailList: http://www.shocker.com/shocker/digests/index.html
              Send the following in the body of an e-mail to list-manager@shocker.com:
                SUBSCRIBE shockwave-DIGEST yourEmail@yourDomain
        Xtras-L (Xtras for Director)
              http://www.gmatter.com/xtras-l.html
              Send the following in the body of an e-mail to listserv@gmatter.com:
                SUB XTRAS-L yourFirstName yourLastName

     Dedication

        Lingo in a Nutshell is dedicated to my wife, Michele, whose love makes my life
        worthwhile.

     Acknowledgments

        I am indebted to many people, some of whom I've undoubtedly omitted from the
        list below. Please buy this book and recommend it to friends so that I can thank
        the people I've forgotten in the next revision.
        My deep appreciation goes out to the entire staff at O'Reilly, whose patience,
        professionalism, and unwavering dedication to quality are directly responsible for
        bringing these books to market. Special thanks go to my editors, Tim O'Reilly,
        Katie Gardner, and Troy Mott, and to Edie Freedman, Sheryl Avruch, Frank Will-
        ison, Nancy Priest, Rob Romano, Mike Sierra, Paula Carroll, Nancy Kruse

        xx Preface
                                                                                                            Preface

Hannigan, Greg deZarn-O'Hare, and all the people who turn a manuscript into a
book. My thanks also to the sales and marketing staff who ensure that my efforts
were not in vain. Last, I want to thank all of the O'Reilly authors whose company I
am proud to be in.

This project would not have happened without the efforts of my agent, David
Rogelberg of Studio B Productions (http://www.studiob.com). He was instrumental
in the development and genesis of both Director in a Nutshell and Lingo in a
Nutshell, for which I am forever grateful. My thanks also to Sherry Rogelberg and
to the participants of Studio B's Computer Book Publishing list.

The quality of the manuscript reflects my excellent technical reviewers, all of
whom made time for this semi-thankless job despite their busy schedules: Lisa
Kushins, who verified items to an extent that astounded me and provided feed-
back that improved every chapter she touched; Hudson Ansley, whose keen eye
and unique perspective also improved the book immeasurably; Mark Castle (http://
www.the-castle.com), who helped shape the style and content from the earliest
stages; and Matthew Pirrone and James Terry (http://www.kandu.com), who both
provided excellent feedback on Chapter 4, Lingo Internals, and Chapter 20, Lingo
for C Programmers, (downloadable from the web site). My thanks also goes out to
all my beta-readers who provided useful feedback, most notably Miles Lightwood
and Birnou Sdarte.

I cannot begin to thank all the Macromedians who develop and support Director,
many of whom provide technical support on their own time on various mailing
lists. My special thanks goes to Buzz Kettles for all his feedback regarding Shock-
wave audio and to Michael Seery for being my inside connection at Macromedia
all these years. My thanks also to Lalit Balchandani, David Calaprice, Jim Corbett,
Landon Cox, Ken Day, Peter DeCrescenzo, David Dennick, John Dowdell, Mike
Edmunds, John Embow, Eliot Greenfield, Jim Inscore, David Jennings, James
Khazar, Leona Lapez, S Page, Bill Schulze, Karen Silvey, Joe Sparks, John
Thompson, Karen Tucker, Anders Wallgren (expatriot), John Ware, Eric Wittman,
Doug Wyrick, and Greg Yachuk, all of whom fight the good fight on a daily basis.

My thanks go out to the wider Director community, including but not limited to
Stephen Hsu, Brian "Bam Bam" Johansen, Peter Fierlinger, Brian Gray, Roger
Jones, Tab Julius, Irv Kalb, Kathy Kozel, Alan Levine, Gretchen Macdowall, Myron
Mandell, Kevin McFarland, Hai Ng, Roy Pardi, Darrel Plant, Peter Small, Kam
Stewart, Stephen Taylor, Andrew White, John Williams, Alex Zavatone, all the
participants of the super-secret mailing lists that I cannot name, and all the users
who have given me feedback over the years, including the AOL old-timers.

Thank you also to Caroline Lovell-Malmberg, who can now forgive her husband,
Mark, for leaving her out of his acceptance speech. Perhaps he'll thank whomever
I've inadvertently left out next time he wins an Oscar.

I'd like to thank you for taking the time to read this book. If I never get around to
stand-up comedy, it is nice to know I still have an audience somewhere. If you
enjoy the book, you owe a debt of gratitude to Professor David Thorburn, who
taught me more about writing than anyone before or since.

Last, I want to acknowledge my entire family, whose sacrifices and support truly
made this book possible. If this book saves you time that you can then devote to

                                                                                            Preface xxi
Acknowledgments
        your family, my efforts will not have been in vain. Good luck in all your multi-
        media pursuits.
              Bruce A. Epstein
              May 1998
              Franklin Park, NJ
              "All the love that you miss...all the people that you can recall...do they really exist at
              all?" -- Lowell George, anticipating Virtual Reality by 20 years

        xxii Preface
         Chapter 1How Lingo Thinks                                                       How Lingo
                                                                                      Thinks
                           CHAPTER 1

               How Lingo Thinks

So You're Too Busy to Learn Lingo

Do you really have time to read a book on Lingo when you're facing a deadline?
The answer depends on how much time you waste struggling with Lingo and how
often you've compromised your Director projects for lack of Lingo skills. If you
make the investment now, this book will pay marvelous dividends. It may save
you weeks otherwise spent flailing over relatively trivial Lingo problems, and it
can help you to add snazzy new features and a professional polish to your
Director projects.

            If you don't have a project to work on, pick one now. You will learn
            much more if you have a concrete goal and concrete problems to
            solve. You have been warned.

Learning to program is a process, not an event. Although this book is not a substi-
tute for an introductory programming class, it covers basic, intermediate, and
advanced topics. The material is very condensed, but the book also lavishes atten-
tion on topics that are omitted entirely from other Lingo books. Before proceeding,
you should understand Director's Cast, Score, and media editing windows, as
covered in Macromedia's Using Director manual. You might also want to skim
Macromedia's Learning Lingo manual for a broad overview of Lingo.
Most books provide simple examples that leave you stranded when you try to
accomplish your specific goals. This book teaches you how to do anything you
want with Lingo, not just create simple clickable buttons. It provides a solid foun-
dation instead of a house of cards, and it is for people who want to know more,
not less. As such, this book explores many abstract concepts that may not be rele-
vant to your immediate needs. You must exercise reasonable discretion by
ignoring topics that don't interest you or are beyond your current level.

                                                     3
So You're Too Busy to Learn Lingo

        This chapter lays the groundwork for your Lingo-laden future, but the details of
        using Lingo to add interactivity are in later chapters (starting with Chapter 2,
        Events, Messages, and Scripts). You should first focus on understanding how Lingo
        itself "thinks." Lingo is a marathon, not a sprint, and the extra training will pay off
        in the long run. More practical examples are given in Chapter 9, Mouse Events, and
        Chapter 10, Keyboard Events. Refer to the companion book, Director in a Nutshell,
        for details on using Lingo to control and analyze cast members, sprites, sounds,
        digital video, MIAWs, fields, and memory.

        You are not expected to understand the entirety of this book the first time you
        read it. Much of it will be meaningless until you've worked with Lingo for a few
        months and encountered specific problems that you wish to solve. At that time,
        you will recall enough to know what sections you need to reread. As in the film
        The Karate Kid, what may seem like meaningless manual labor is really your first
        step toward a black belt in Lingo. You should revisit this and other chapters peri-
        odically. They will reveal additional nuggets of knowledge as your experience and
        problems with Director and Lingo grow. Certainly, you should return to the appro-
        priate chapter whenever you encounter a vexing problem, as the chances are high
        that the answer lies herein.

        Even if Lingo is your first programming language, this chapter will help you to
        understand other people's Lingo code (which is the first step in creating your
        own). This chapter unavoidably introduces many new concepts that depend on
        other material not introduced until later (the old "chicken and the egg" problem).
        Skip around the chapter as necessary, and consult the Glossary whenever you feel
        queasy. Keep in mind that this chapter is intended to satisfy a broad range of
        users, some with much more programming experience than others. Skip the mind-
        numbing sections that don't have relevance for you yet (but revisit them later).
        Above all, do not lose heart. If you keep reading, you'll encounter the same
        concepts again, and they will eventually make sense. In the words of Owl, "Be
        brave, little Piglet. Chin up and all that sort of thing."

        The example code used throughout this book is available from the download site
        cited in the Preface, but you should create a test Director movie file and type in
        the shorter examples by hand. Add the examples in each chapter to your test
        movie and use it like a lab notebook full of your experiments. This practice will
        make it much easier to write your own Lingo when the time comes. You might
        want to maintain a separate test movie for each chapter; start with a fresh movie
        (to eliminate potential conflicts) if an example doesn't seem to work.

                    You must abandon the safety of spoon-fed examples and experi-
                    ment. If at first you don't fail, try, try again. You will learn more
                    from failure than from success.

        Experienced programmers can skim most of this chapter but should read the
        sections entitled "Recursion," "Dynamic Script Creation," "The Classic Three-Line If
        Statement," "Special Treatment of the First Argument Passed," and "Variable-Length
        Parameter Lists." Also see Chapter 4, Lingo Internals.

        4 Chapter 1  How Lingo Thinks
                                                                                         Lingo Scripting Basics   How Lingo
                                                                                                               Thinks
Let us set our goals high and see if we can stretch our minds to reach them. Let us
now commit ourselves not only to learning Lingo, but also to becoming true
Linguists, as fluent in Lingo as we are in our own native tongues.
Like all experienced Linguists, you should first build a shrine to the Lingo Gods
with an altar for burning incense to summon and appease them. Abandon all
hope, ye who enter here, for there is no turning back.

    "Do or not do. There is no try."--Yoda

Lingo Scripting Basics

Computer languages tend to be simpler and more rigid than human languages, but
like any other language Lingo has a set of rules that control the structure (syntax)
of your Lingo program. Just as languages have grammar, Lingo's syntactical rules
restrict the spelling, vocabulary, and punctuation so that Director can understand
your instructions.

            A syntax error or script error usually indicates a typographical error
            or the incorrect use of a Lingo statement.

Lingo's built-in keywords (or reserved words) make up Lingo's vocabulary and are
the building blocks of any Lingo program. We'll see later how these keywords
form the skeleton of your Director program, just as any language's words are the
basis for sentences and paragraphs. It is crucial that you recognize which items in
a Lingo script are built-in keywords versus those that are specified arbitrarily by
the programmer. Refer to Chapter 18, Lingo Keyword and Command Summary, for
a complete list of all Lingo keywords. The PrettyScript Xtra (http://rampages.
onramp.net/~joker/tools/) is a $20 U.S. shareware tool that colorizes some items in
your Lingo scripts to make them easier to recognize. The ScriptOMatic Lite Xtra, is
available under XtrasScriptOMaticLite, colorizes a broader range of items,
but it is crippled almost to the point of being useless. The full version is promised
imminently from g/matter (http://www.gmatter.com/products/scriptomatic/) at press
time.

Handlers and Scripts

A handler is a series of Lingo statements that tell Director to perform some useful
function. Handlers are typed into script cast members in the Script window.
("Script" is also used loosely to refer to a handler within a script. "Code" is used
both as a noun to indicate your Lingo scripts and as a verb, meaning "to program"
or "to write Lingo scripts.")
The scripts in a Director movie control the action, just as real-life actors follow a
script. There are several types of scripts (castmember scripts, movie scripts, sprite
scripts, parent scripts, and Behaviors), which are covered in detail in the "Lingo
Scripts and Handler Types" section of Chapter 2.

                                                                           Lingo Scripting Basics 5
Lingo Scripting Basics

       Hello World

        As required by the International Programmers' Treaty of 1969, we'll start with an
        example that displays "Hello World." Open up a movie script cast member using
        Cmd-Shift-U (Macintosh) or Ctrl-Shift-U (Windows).

        Enter Example 1-1 exactly as shown into the movie script window.

        Example 1-1: Hello World

         on helloWorld
             alert "Hello World"

         end

        The keyword on identifies the beginning of our handler, which we arbitrarily
        chose to name helloWorld. The keyword end signifies the end of our handler.

                    The examples beginning with the word on are handlers that must be
                    typed into a script, not the Message window.
                    With minor exceptions, your Lingo code for each handler goes
                    between the on handlerName and end commands (see "Where
                    Commands Go").

        Handler names must be one word, but they are case-insensitive, so you can use
        capitalization to make them easier to read. Name your handlers descriptively so
        that you can remember what they do, and as a rule you should avoid naming
        them the same as existing Lingo commands (see Table 18-1).

        A handler name must start with an alphanumeric character, not a digit, but it can
        contain digits, decimal points, and underscores. Only the first 260 characters of the
        name are significant.

        Movie script cast members are simply repositories for our handlers and are not
        used in the Score (see Chapter 2 for details on score scripts).
        Entering a handler into a script (as shown above) defines or declares the handler
        and is referred to as a handler definition. Defining (declaring) a handler makes it
        available for future use, but the handler doesn't execute until something tells
        Director to run it for you.
        Close the Script window to compile it (that is, to prepare it to run). When the
        handler is run (called), Lingo will execute each line (that is, each command) in
        the order in which it appears in the handler. There is only one command in our
        helloWorld handler; the built-in alert command displays the specified text in an
        alert dialog box.
        The Message window provides an area for printing messages from Lingo and
        testing Lingo scripts (see Chapter 3, Lingo Coding and Debugging Tips). A handler
        stored in a movie script can be executed (called) by typing its name in the
        Message window (or by using its name in another handler).

        Open the Message window using Cmd-M (Macintosh) or Ctrl-M (Windows). In the
        Message window, type the name of the handler to test (helloWorld without any

        6 Chapter 1  How Lingo Thinks
                                                                                         Lingo Scripting Basics   How Lingo
                                                                                                               Thinks
spaces). Do not precede the name with the word on, which is used only to
declare a handler, not to run it.

      helloWorld

            Always press the RETURN key (Macintosh) or the ENTER key (Win-
            dows) at the end of the line to initiate the command. Example code
            shown flush left should be typed into the Message window, as
            opposed to handler definitions that are entered in the Script window.

Congratulations, you are now a Lingo programmer! After accepting your diploma,
please step to the right. If your script didn't work, make sure you typed every-
thing correctly and that you entered the script in a movie Script window (not a
score script, castmember script, field, or text cast member). Choose
ControlRecompile All Scripts. If it still fails, hang your head in shame, or
see Chapters 3 and 4.

Calling All Scripts
Typing helloWorld in the Message window calls (locates and runs) the handler
of the same name. Reopen the script, and change both the name of the handler in
the script and the name you type in the Message window to something new. If the
names don't match, what happens? Did you remember to recompile the script by
closing its window? Set the Using Message Window Recompiles Scripts option under
PreferencesGeneral to ensure that the latest version of a handler is executed.
See "Compiling Scripts" later in this chapter.
Note above that "Hello World" is automatically incorporated by the alert
command into the alert dialog. You can change the displayed text by specifying
any string (series of characters) in place of "Hello World" (don't forget the
quotes). The specified string is said to be an argument to the alert command, and
it is used to customize the dialog. See "Commands and Functions" and "Parame-
ters and Arguments" later in this chapter for complete details on using arguments
with built-in Lingo commands and custom handlers.
Previously we created an arbitrarily named custom handler and called it from the
Message window by using its name.

            You can add more handlers after the end of the helloWorld handler
            in the movie script used above, or you can press the "+" button in
            the Script window to create a second movie script. (You can have a
            virtually unlimited number of movie scripts).

Naturally, the user will not be typing anything in the Message window. When the
user clicks the mouse button or presses a key Director tries to run handlers named
on mouseDown, on mouseUp, on keyDown, and so on. In practice, you'll create
event handlers with these reserved names to respond to user events. If you name

                                                                           Lingo Scripting Basics 7
Lingo Scripting Basics

        the handlers incorrectly, they will never be executed. See the "Events" section in
        Chapter 2, and Chapter 9 for more details.

       Nested Handler Calls

        Just as we can call a handler from the Message window, one handler can call
        another simply by using its name. As each handler completes its work, control
        returns to the calling handler. You can picture a hierarchy of nested handler calls
        as an outline that periodically is indented further, then returns to the previous
        level. Suppose we define several handlers (some of which call other handlers) in a
        movie script as shown in Example 1-2.

                    The put command prints a message in the Message window and is
                    used throughout the book to peek inside Lingo. The && and & oper-
                    ators are used to assemble long strings (see Chapter 7, Strings).
                    Lingo lines starting with two hyphens ("--") are comments for the
                    reader's benefit (see "Comments," later in this chapter).

Example 1-2: Nested Handler Calls

   on handlerA

   -- Print a status message

   put "I'm in handlerA"

   -- Call a different custom handler

   handlerB

   put "I'm back in handlerA"

   -- Call another custom handler

   handlerC                        1

   put "I'm back in handlerA one last time"

4  end

              on handlerB
                  put "I'm in handlerB"
                  handlerD
                  put "I'm back in handlerB"

              end
                                           2

              on handlerC
                  put "I'm in handlerC"

              end

3
              on handlerD
                  put "I'm in handlerD"
              end

   on handlerE
      put "I'm in handlerE"

   end

8 Chapter 1  How Lingo Thinks
                                               Lingo Scripting Basics

We can then test it from the Message window.                                             How Lingo
                                                                                      Thinks
      handlerA
      -- "I'm in handlerA"
      -- "I'm in handlerB"
      -- "I'm in handlerD"
      -- "I'm back in handlerB"
      -- "I'm back in handlerA"
      -- "I'm in handlerC"
      -- "I'm back in handlerA one last time"

The series of Lingo handlers that are currently "pending" is known
as the call stack. The call stack is always shown in the upper left
pane of the Debugger window (see Figure 3-1).

Note that handlerA calls handlerB, which then calls handlerD. Control then passes
back through handlerB and back to handlerA. Finally, handlerA calls handlerC,
and control is then returned to handlerA. Conceptually, this can be pictured as:

      handlerA
          handlerB
              handlerD
          handlerC

Note that the order of execution within a handler is determined by order of the
Lingo commands, but the order in which the four handlers are typed into the
movie script is irrelevant. Execution begins at our so-called entry point (in this
case handlerA, which was called from the Message window), and Lingo takes
detours into each called handler before it returns control to the calling handler.
Note that handlerE is never called and therefore never executed, even though it
has been defined in the same script with our other handlers.

Recursion

Each time a handler is called, a copy of it is created temporarily. The copy comes
into existence when the handler is called and disappears when the handler
completes. You can call a handler hundreds of times, and each occurrence will be
independent of the other occurrences. A handler that calls itself, as shown in
Example 1-3, is called a recursive function, and this technique is called recursion.

If we call our recursive function from the Message window, Director
will run out of memory. (Save your work before testing this as it
may crash your machine.)

Example 1-3: A Recursive Function

on recurseTest
   recurseTest

                                               Lingo Scripting Basics 9
Lingo Scripting Basics

        Example 1-3: A Recursive Function (continued)

             put "End of recurseTest reached"
         end recurseTest

        If you are using recursion, it is probably an accident. As a general rule, you should
        avoid it. It is like a reflection repeated infinitely between two mirrors; in the
        extreme case it will crash Director. See Example 6-9, "Recursively Sorting Sublists
        in Chapter 6, Lists, Example 8-16, "Recursive Factorial Function" in Chapter 8,
        Math (and Gambling), and Example 14-5, "Extracting Files in Subfolders" in
        Chapter 14, External Files, for proper uses of recursion.

        Even if we call recurseTest only once, it calls itself repeatedly so that Director
        keeps going "down" an extra level and never comes back up for air. Director will
        run out of memory before the put "End of recurseTest reached" command is ever
        reached. Note that each time recurseTest is called, it spawns another copy of itself.
        Conceptually, this can be pictured as follows:

                recurseTest
                    recurseTest
                       recurseTest
                           recurseTest
                               (ad infinitum until Director runs out of memory)

        Note that it is perfectly acceptable for one handler to call another repeatedly, as is
        often done using a repeat loop (see "Repeat Loops" later in this chapter).

        Example 1-4: Calling a Function Non-recursively

         on testIt
             repeat with i = 1 to 100
                 someHandler
             end repeat

         end

         on someHandler
             put "I am inside someHandler"

         end

        Typing testIt in the Message window will print out "I am inside someHandler"
        100 times with no ill effects because each time someHandler completes, control is
        returned to the top level (in this case, the testIt handler).

      Entering and Compiling Scripts

        There is no magic to entering Lingo scripts. Scripts are typed in script cast
        members (or attached to non-script cast members) via the Script window. Script
        cast members appear in the Cast window along with your other assets (bitmaps,
        fields, and so on). The Script and Message windows include buttons to access
        pop-up menus of Lingo commands (both alphabetical and by category). You can
        use these to insert commands into your scripts or to remind you of the correct
        syntax. Refer to Chapter 2 of this book and to Chapter 2, Script Basics, of Macro-
        media's Learning Lingo manual for details on creating scripts and entering your
        Lingo.

        10 Chapter 1  How Lingo Thinks
                                                                                         Lingo Scripting Basics   How Lingo
                                                                                                               Thinks
Where Commands Go

All your Lingo code goes between a handler's on handlerName and end
statements.
The exceptions to the rule are:
 Each handler should be separate from other handlers. Handler declarations

      are not "nested" the way that if...then statements can be. Do not start a new
      handler before end'ing the first one, as described under "Common Handler
      Declaration Errors" later in this chapter.
 Comments can be placed both inside and outside handlers.
 Property variables must be declared outside any handler.
 Global variables can be declared both inside and outside handlers. Global
      variables declared within a handler apply only to that handler. Global vari-
      ables declared outside a handler apply to all handlers in the script following
      the declaration.
Each Lingo command occupies its own line (although there are some multiline
Lingo statements, discussed under "Multiline Code Structures" later in this chapter).
Each line of Lingo is separated using a carriage return--that is, using the Return
key (Macintosh) or Enter key (Windows) on the main keyboard, not the one on
the keypad.
You can enter long lines of Lingo code in your script without line breaks; Director
will wrap them automatically. To improve readability (as with many examples in
this book), long lines of Lingo code can be continued onto the next line using the
Lingo continuation character , as shown in the example that follows. This special
character is created using Option-Return (Macintosh) or Alt-Enter (Windows).
      -- Here is a long line of Lingo broken onto two lines
      set the member of sprite (the currentSpriteNum) = 

            member "Hilighted Button"
You can break long lines of Lingo onto more than two lines using an  character
at the end of each line (except the last) of the long command. Do not break the
long lines (that is, do not use the  character) within quoted strings (see
Chapter 7, Strings). Do not put anything, even a space, on the same line after a
continuation character.
Director ignores leading spaces and automatically indents your Lingo code
according to its own rules. For example, all lines within a handler between the on
and end statements are indented at least two spaces. Use the same font and type
size throughout the script to make the code more legible and indentation prob-
lems obvious. Colorized or formatted text can slow the Script window's response,
especially for longer scripts. A single script cast member is limited to 32,000 char-
acters, but you can use as many script cast members as required.

                                                                          Lingo Scripting Basics 11
Lingo Scripting Basics

                    Use the Tab key to automatically indent your Lingo code. If the
                    indentation is wrong, you may have omitted necessary keywords or
                    used them in the wrong order. Refer to "Lingo's Skeletal Structure"
                    later in this chapter.

        The Lingo code you enter is simply text (although you should enter it in a script
        cast member, not in a text or field cast member). Before it can be run, Director
        must compile your Lingo code into a machine-readable format. (This is analogous
        to a player piano, which cannot read sheet music but can play a song if is tran-
        scribed onto a paper roll.)

        When Director compiles a script, it checks that the syntax conforms to the
        accepted rules and does its best to parse (understand) the structure of your Lingo.
        Compilation is analogous to spellchecking and grammar checking in a word
        processor. It merely checks that your Lingo code has a recognizable structure and
        acceptable keywords. It does not attempt to actually run your Lingo code.

        It would be counter-productive for Director to attempt to compile your scripts as
        you type them. Use ControlRecompile All Scripts to compile your scripts
        when you finish typing (see "Compiling Scripts" in Chapter 2).

        If Director's compiler fails, it displays a script error (a syntax error) that identifies
        the offending portion of the Lingo, but it may merely reflect a problem that lies
        elsewhere. You would then correct the Lingo and recompile. If successful, it
        creates a hidden compiled version of your Lingo script that runs more quickly than
        it would if Director had to reinterpret your human-readable script every time it
        runs.

        If compilation succeeds, your code is not necessarily error-free and may still cause
        a so-called runtime error when Director attempts to run it. (In this context runtime
        refers to when the script is executed, as opposed to when it is compiled. This
        should not be confused with authoring time (in Director) vs. runtime (in a
        Projector). Refer to Chapter 3 for more details.

      Handler Scope

        Handlers are stored in script cast members (excepting those attached directly to
        other member types); the multiple types of script cast members are explained in
        great detail in Chapter 2. The script cast member's type (movie script, score script,
        or parent script) affects the scope of all the handlers declared within it (that is,
        which other scripts can "see" these handlers and from where they are accessible).
        We were able to test the example handlers above from the Message window
        because they were entered in movie scripts. (A movie script is a script cast member
        whose type is set to Movie in the script cast member's info window). Handlers in
        movie scripts can be "seen" from the Message window or any other script in the
        same Director movie (even from scripts in other linked castLibs) because they
        have universal scope.

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Had we entered the example handlers in score scripts, attempting to use them
from the Message window would result in a "Handler not defined" error because
the scope of score scripts is more limited.
If two handlers in the same script cast member have the same name, Director will
complain. Neither should you use two handlers with the same name in two
different movie scripts because the first handler found will intercept all function
calls using that name, and the second handler will always be ignored.

            Place any handlers that you use in multiple Director movies or multi-
            ple Director projects into movie scripts in an external cast library that
            you can link into your project. Use unique names, perhaps starting
            with a prefix such as "lib," that are unlikely to conflict with other
            handlers in a given movie.

Avoid naming your handlers the same as existing Lingo commands (see
Table 18-1). A custom handler (stored in a movie script) that has the same name
as a built-in Lingo command will intercept (and override) any calls to that Lingo
command. If accidental, such an error can be extraordinarily hard to debug.
Contrary to movie scripts, it is very common to use handlers of the same name in
score scripts. (Again, these are explained in detail in Chapter 2.) The important
point is that the handlers in score scripts have a different scope (accessibility) than
handlers in movie scripts. For example, most sprite scripts (one type of score
script) will contain on mouseUp handlers, and most frame scripts (another type of
score script) will contain on exitFrame handlers. The same handler name can be
used in multiple score scripts because they do not have universal scope as do
handlers in movie scripts. Director automatically calls only those handlers that are
attached to the current frame or the sprite on which the user clicked. Other on
mouseUp and on exitFrame handlers located in other score scripts won't interfere.
Refer to Chapter 9 for more details. Likewise, Lingo calls an on keyDown handler
only if it is attached to the field sprite that has keyboard focus (see Chapter 10).
Example 1-5 demonstrates the different scope of a handler depending on the script
type in which it exists.
If the following two handlers coexist in the same score script cast member,
handlerA can call handlerB (or vice-versa).

Example 1-5: Handler Scope

on handlerA
   handlerB

end

on handlerB
   put "I am doing something, so please stop hovering."

end

                                                                          Lingo Scripting Basics 13
Lingo Scripting Basics

        If the two handlers existed in two separate score scripts, however, they would not
        "see" each other and therefore could not call each other. On the other hand, if
        handlerA was in a score script, but handlerB was in a movie script, handlerA
        could call handlerB, but not vice-versa. Furthermore, if handlerB is in a movie
        script, it can be called from other handlers in other scripts of any type. Therefore,
        you should place one copy of your general-purpose utility handlers in a movie
        script rather than replicating it in multiple score scripts.

                    Handlers in movie scripts can be called from anywhere at any time
                    and are usually custom handlers named arbitrarily by the program-
                    mer. Handlers in score scripts are generally named to respond to
                    predefined events (such as mouseUp) and are called by Director in
                    response to those events.

        This example offers a simplified picture of the universe. In actuality, any handler
        in any script can be called from anywhere if you refer to the script explicitly. You
        usually refer only to the handler name and let Director decide in which script to
        find the handler. This is covered in Chapter 2, along with details on the way that
        handlers in multiple scripts are sometimes called in succession.
        See "Special Treatment of the First Argument Passed" later in this chapter for details
        on how the first argument to a function affects which scripts are searched for a
        matching handler.

      Commands and Functions

        A command tells Director to do something, such as play a sound, but usually does
        not return any result. Built-in Lingo keywords are referred to as commands, but
        you can create custom handlers that are used just like the built-in commands,
        essentially extending Director's command set. (The word command is also used
        loosely in many contexts, including to indicate a menu choice.)
        The general format of a command is:

                commandName arg1, arg2, arg3, ...
        where the arguments (arg1, arg2, arg3, ...) are inputs used by the command,
        and may be optional or mandatory, and vary in number and type depending on
        the command. For example, the alert command shown previously expected a
        single string argument. The puppetSprite command expects two arguments (an
        integer and a Boolean value), as in:

                puppetSprite 17, TRUE
        A command that returns a result is called a function (the terms, though, are often
        used interchangeably). The result may be a number, a string, or any other data
        type. The general format of a function is

                set variableName = functionName (arg1, arg2, arg3, ...)
        or

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      put functionName (arg1, arg2, arg3, ...) into variableName
where again the arguments (arg1, arg2, arg3, ...) may be optional or mandatory
and may vary in number and type depending on the function.
For example, the power() function requires two arguments and raises the first
argument to the power specified by the second argument. You wouldn't ordi-
narily compute a value and discard the result; you would either print it out in the
Message window or store it in a variable (a container for data). Below, the result
of the calculation is stored in a variable that is arbitrarily named myValue (see
"Variable Storage Classes and Data Types" later in this chapter for details on
variables).

      set myValue = power (10, 2)
If you don't store the result in a variable, the function still returns a result that can
be used in other expressions (see Chapter 5, Data Types and Expressions). This
prints the result in the Message window instead of storing it in a variable:

      put power (10, 2)
      -- 100.0000
This uses the result of the calculation to decide whether to print a message:

      if power (10, 2) > 50 then put "That's a big number."
In some cases, Director issues a "Command not defined" error if you use a func-
tion by itself rather than as part of a larger expression:

      power (10, 2) -- This causes an error
Either use put power (10, 2) to print the result of the function call in the Message
window or assign the result to a variable, as shown earlier.
If a function does not require any arguments, you must still include the paren-
theses to obtain the result, such as:

      put browserName()
      -- "Mac HD:Netscape Navigator Folder:Netscape Navigator"
See "Return Values and Exiting Handlers" later in this chapter for details on
returning values from custom handlers.
Lingo allows nested function calls, in which the result of one function is used as
an argument to another function, such as:

      if (random(max(x, y)) > 5) then ...
In such a case, the result of max(x, y) is used as an argument to the random()
function. The preceding code is just shorthand notation for:

      set myValue = max(x, y)
      if (random(myValue) > 5) then ...

Return Values and Exiting Handlers

This section is next in the logical progression of the chapter, but it will not make
sense unless you understand concepts explained later. You can skim it now and
revisit it after reading the rest of the chapter. As alluded to earlier, a handler often

                                                                          Lingo Scripting Basics 15
Lingo Scripting Basics

        performs a calculation and returns the result to the calling routine. A handler or
        Lingo command that returns a value is called a function. Most functions require
        some inputs on which to operate (see "Parameters and Arguments" for details).
        For example, the built-in Lingo function max() returns the maximum value from
        the list of items you send it:

                put max (6, 9, 12)
                -- 12

        You might write your own custom function that returns TRUE or FALSE based on
        whether the input is a valid digit between 0 and 9, as shown in Example 1-6.

        Example 1-6: Returning a Value from a Function

         on isDigit someChar
             if "0123456789" contains string (someChar) then
                 return TRUE
             else
                 return FALSE
             end if

         end isDigit

        In this case, the result (1) signifies the Boolean value TRUE:

                put isDigit (5)
                -- 1

The parentheses surrounding the arguments are mandatory when
calling a function that returns a value. Even if the function does not
require any parameters, you must still include the parentheses to
obtain a result.

If the parentheses are omitted, Lingo would treat isDigit as if it were a variable
name (see "Variables and Properties" later in this chapter) rather than a function
name. In the following case, isDigit is mistaken for a VOID (valueless) variable,
and the put statement prints the values VOID and 5 instead of the desired result of
the function call.

put isDigit 5
VOID 5

Note the use of parentheses following rollover():

put rollOver()  -- rollOver() is treated as a function call
-- 7            -- rollOver is treated as a variable name
put rollOver
-- VOID

Leaving the Current Handler

Ordinarily a handler terminates when the last statement in it is reached (the end
statement). Control then returns to whatever called the handler (either another
handler or Director itself). In that case, no value is returned to the calling handler,

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and any calculated result would be lost unless it were stored in a global or prop-
erty variable. The return and result commands obtain return values from a
handler. The abort and exit commands terminate a handler prematurely. (They
differ from next repeat and exit repeat, which affect program flow but do not exit
the handler). The quit, halt, restart, shutDown, go, play, play done, and pass
commands may also affect the order of Lingo execution.

return
      The return command exits the current handler and returns control to the
      calling routine, along with an optional value of any data type. Any statements
      following the return are not executed, which makes return convenient for
      exiting a handler once a particular condition is met or task is completed.
      Example 1-7 returns as soon as it finds a sound cast member in the primary
      castLib. It returns zero (0) if no sound cast member is found. The other details
      are not important at this point.

Example 1-7: Returning Prematurely from a Function

on findFirstSound
    -- Loop through the cast
   repeat with n = 1 to the number of members
      -- Look for a sound castmember
       if the type of member n = #sound then
          -- Return the number of the sound
          -- and we're out of here!
          return n
       end if
   end repeat

    -- If no sound was found, return 0
   return 0
end findFirstSound

Test it in the Message window:

      put findFirstSound()
      -- 72

            The above technique is best used with small handlers. Avoid using
            multiple return statements to exit a large handler from many differ-
            ent points. It makes the code harder to understand and maintain.
            Storing the eventual return value in a variable and returning it at the
            end of the handler is often clearer.

      You can use return without a value, in which case it is identical to exit, and
      the caller receives VOID as the returned value. Note that the return command
      is distinguished by context from the RETURN constant (which indicates the
      carriage return character).

                                                                          Lingo Scripting Basics 17
Lingo Scripting Basics

        the result
              The result retrieves the result of the last function call, even if it was never
              stored in a variable when it was returned by the last function call.

                set x = isDigit (5)
                put x
                -- 1
                isDigit (5)
                put the result
                -- 1
              Some commands, such as preLoad and preLoadMember, do not return a value,
              but set the result.

                preLoadMember 1, 5
                put the result
                -- 5

        abort
              Abort aborts the call stack (that is, the current Lingo handler and any
              handlers that called it) without executing any of the remaining Lingo state-
              ments in any of those handlers. By contrast, exit exits only the current
              handler. Abort is useful when you want to stop the current action in response
              to some drastic change. For example, if the user presses the Escape key, you
              may abort what you are doing:

                on getUserInfo
                    -- Abort if the user hits ESCAPE (ASCII code 27)
                    if the key = numToChar (27) then
                       abort
                    end if

                end getUserInfo
              Abort does not quit Director (see halt or quit), nor does it abort asynchro-
              nous operations in progress (see cancelIdleLoad, netAbort). Abort aborts only
              Lingo execution; it does not affect the Score's playback head (see the pause
              command).

        exit
              Exit (not to be confused with exit repeat) causes Lingo to exit the current
              handler. It exits "up" only one level to the calling handler, as opposed to
              aborting the entire call stack (see "Nested Function Calls" earlier in this chapter).
              Exit is often used to exit the current handler if some condition is not met:

                on playVideo
                    if not (the quickTimePresent) then
                       alert "You can't play video without QuickTime."
                       exit
                    end if
                   -- Remaining statements are run only
                   -- if QuickTime is installed.

                end playVideo
              When using exit, no return value is sent. Use return instead to return a value
              to the calling handler.

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quit, halt, restart, and shutDown
      Quit and halt immediately quit a Projector and are generally used only in a
      script attached to a Quit button or at the end of a presentation. During devel-
      opment, halt stops the movie without quitting Director. See Chapter 8,
      Projectors and the Run-time Environment, in Director in a Nutshell for details
      on these and other commands, including restart and shutDown.

go
      The playback head moves semi-independently remaining of Lingo commands.
      If you use the go command to move the playback head, commands in the
      handler are still executed before jumping to the new frame.

      on exitFrame
          go frame 50
          put "This will be printed before jumping to frame 50"

      end

play and play done
      The play command works differently than the go command. Commands
      following the play command are executed, but not until a play done
      command returns control back to the original script. Commands following
      play done are never reached. Test this using a frame script of the form:

      on exitFrame
          play frame 50
          put "This will be printed second, not first"

      end
      In frame 50, use this frame script to complete the test:

      on exitFrame
          put "This will be printed first"
          play done
          put "This line won't ever be reached or printed"

      end

pass
      The pass command aborts the call stack (see the abort command). Commands
      following the pass command are never executed. Control immediately jumps
      to the next script that handles the event being passed (see Chapter 2). For
      example:

      on mouseUp
          pass
          put "This line won't ever be reached or printed"

      end

Dynamic Script Creation

This section is next in the logical progression of the chapter but is fairly
advanced--and irrelevant for most users. You can skim it or even ignore it alto-
gether without significant regret. You can create new Lingo dynamically at runtime
(that is, while Director or even a Projector is running). Using the do command or
by setting the scriptText of member property, you can actually create new Lingo
from within Lingo! You can dynamically evaluate a string as if it is a Lingo state-
ment using the value() function. Most programming languages don't allow this,

                                                                          Lingo Scripting Basics 19
Lingo Scripting Basics

        and you will rarely use this feature. The following examples are for illustration
        only and do not necessarily depict likely uses.

       Do Statements
        The do command can compile and execute a string on the fly as if it were a Lingo
        statement. Although it should not be used haphazardly, it can perform some inter-
        esting tricks. Most notably, you can use it to execute an arbitrary command stored
        in a text file or a field cast member. You can create a pseudo-Message window for
        debugging Projectors by do'ing the text entered in a field cast member:

                do "beep"
                do the text of field "someFieldCastMember"
        You cannot use do to declare global variables without a trick. The following will
        not work:
                do "global gSomeGlobal"
                do "set gSomeGlobal = 5"
        To declare a global with a do statement, use:
                do "global gSomeGlobal" & RETURN & "set gSomeGlobal = 5"
        To make use of a global within a do statement, declare the global inside the
        current handler. So-called "global globals" declared outside the currrent handler
        are not recognized during a do statement. The following example is illustrative
        only and would never be required in reality:
                on setGlobal

                    global gSomeGlobal
                    do "set gSomeGlobal = 7"
                end

       Value Statements
        The value() function can be used to convert a string into an integer or a float, as is
        useful when converting string data from a file or user input into a number.

                set userEntry = value (field "Age in Years")
        Value() can also evaluate a string or symbol as if it is a variable name:

                set someVar = "Oh happy days!"
                put value ("someVar")
                -- "Oh happy days!"
                put value (string(#someVar))
                -- "Oh happy days!"

       Setting the ScriptText at Runtime
        The scriptText of member property contains the Lingo code from a script cast
        member. The human-readable form of the scriptText is stripped when creating
        Projectors and protecting DIR files (creating DXR files), leaving only the hidden

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internal compiled version. Even from a Projector, you can create a script dynami-
cally, as shown in Example 1-8.

Example 1-8: Creating Scripts at Runtime
-- Set up a string variable containing the text:
on createscript

   set dynaScript = "on newHandler" & RETURN 
                                      "global gMyGlobal" & RETURN 
                                      "set gMyGlobal to 52" & RETURN & "end"

-- Create a new movie script cast member, and fill it in.
   set newMovieScriptCastMember = new(#script)
   set the scriptType of newMovieScriptCastMember = #movie
   set the scriptText of newMovieScriptCastMember = dynaScript

end
-- Now you can run it
createscript
newHandler
-- If desired, you can then delete the cast member
erase newMovieScriptCastMember

Variables and Properties

You'll often read Lingo properties to obtain information about the user or the run-
time environment and set properties to affect the run-time environment. You'll use
variables as containers to store and manipulate any type of data, including Lingo
properties. Later we'll see how you can define your own properties using so-called
property variables, which are a particular type of variable but are unrelated to
Director's built-in properties.

Built-In Lingo Properties and Constants

Lingo defines dozens of properties (not to be confused with programmer-defined
property variables, discussed later), which are always preceded by the keyword
the.

            If you omit the word the, Lingo thinks you are referring to a pro-
            grammer-defined variable, not a Lingo property.

A property may pertain to the overall system, the current movie or MIAW, a cast
member, or a sprite. Lingo properties are universally accessible (they can be used
from any script at any time), and they may be static (fixed) or may change over
time or based on user actions. For example, the platform property doesn't change
unless you switch computers, but the mouseH and the mouseV properties change
whenever the cursor moves.
The general format for setting a Lingo property is:

      set the property {of object} = value

                                                                      Variables and Properties 21
Variables and Properties

        or

                put value into the property {of object}
        where value is replaced with a meaningful value, property is a property name
        and object is usually a sprite, member, or window reference. The following
        examples set the locH of sprite sprite property, the regPoint of member member
        property, and the soundEnabled system property. Note that all three properties
        start with the, although no object is specified for the soundEnabled property
        because it is a system property, not a property of a sprite or a cast member.

                set the locH of sprite 1 = 17
                set the regPoint of member 1 = point(0,0)
                set the soundEnabled = TRUE
        The general format for reading a Lingo property is:

                set variableName = the property {of object}
        such as:

                set spritePosition = the locH of sprite 1
                set memberDepth = the depth of member 1
                set mousePosition = the mouseH
        Some Lingo keywords are constants (fixed values) that don't use the word the,
        such as PI, TAB, and SPACE. See Table 5-6.

       Common Errors When Using Properties and Constants

        The following are common errors when using properties. Refer also to "Common
        Errors When Using Variables" later in this chapter.
        Forgetting the word the:

              The following sets stage white by setting the stageColor property to zero:
                set the stageColor = 0
              However the following defines a local variable, stageColor, and assigns it
              the value zero, which is probably not the desired goal.
                set stageColor = 0
              Using a property without the preceding the will cause a "Variable used before
              assigned a value" error, such as:
                if mouseV > 50 then put "The mouseV is greater than 50"
              (This won't fail in the Message window, but it will fail from within a script).
        Confusing a local variable with a property of the same name:
              Here, mouseH is a local variable, whereas the mouseH is a Lingo property. As
              the mouse continues to move, the property the mouseH will change, but the
              variable mouseH won't change without your explicit instruction.
                set mouseH = the mouseH
              Use variable names that are different from Lingo property names to avoid
              confusion, such as:
                set lastMouseH = the mouseH

        22 Chapter 1  How Lingo Thinks
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Confusing a variable with a Lingo constant of the same name:
      Some keywords are reserved constants (see Table 5-6) that never change in
      value, even if you inadvertently try to assign a new value to them. For
      example, you cannot change the value of pi.
      set pi = 54.36
      put pi
      -- 3.1416

Some properties can not be set:
      Many properties can be both set and read, but some can be only read. The
      "Cannot set this property" error may result if you attempt to set a property that
      is read-only, such as the mouseH. Other properties may appear to be settable,
      but setting them may have no effect. For example, setting the colorDepth
      under Windows, or to an invalid value on the Macintosh, will leave the
      monitor depth unchanged, although no error results.

Using a "stale" value of a property that has changed:
      Many Lingo properties change based on conditions beyond the programmer's
      control. For example, the shiftDown property changes whenever the user
      presses or releases the Shift key, and it may even change during the execu-
      tion of, say, your on keyDown handler. If necessary, store the current value of
      a property in a variable (see details that follow), such as:
      set shiftKeyState = the shiftDown

Version

There is a single Lingo global variable (global variables are explained later) named
version that returns Director's version number (as a string) and can not be set nor
cleared with clearGlobals. Do not use the name "version" as a variable name.
Use version as follows:

      on testVersion
          global version
          put "The current version is" && version

      end testVersion

      testVersion
      -- "The current version is 6.5"
Director also supports the property the productVersion, which doesn't require a
global declaration (although the two methods return different values in
Shockwave).

      put the productVersion
      -- "6.5"

Using Variables

A variable is a container for any type of data (such as an integer or a string) that
usually stores values that may change or are not known until runtime. You are the
master of your own variables. You can create as many as you need and give them

                                                                      Variables and Properties 23
Variables and Properties

        whatever names you like. For example, you might store the user's name and his
        high score in separate variables named userName and highScore.

                    Variables are not the algebraic "unknowns" that gave you night-
                    mares in school. They are just convenient placeholders that allow
                    your scripts to be flexible. Variables, unlike built-in Lingo proper-
                    ties, change only at your behest.

        Once you've stored a value in a variable (see the next section) you can obtain that
        value simply by referring to the variable by name. See "Data Types and Variable
        Types," "Type Assignment and Conversion," and "Constants and Symbols" in
        Chapter 5 for more details on variables.

       Assigning a Value to a Variable, Property, or Field
        You store data in a variable, property, or field by assigning a value to it in one of
        the following ways:

                set item = value
                set item to value
                put value into item
        where item is a variable name, property (such as the colorDepth), or a field refer-
        ence (such as field "myField").
        I strongly recommend the first form (set item = value) because it clearly delineates
        the variable or property on the left side of the expression from the value being
        assigned to it on the right side of the expression. For example:
                set x = 5
                set x = char 1 to 5 of "hello there"
                set the soundEnabled = TRUE
                set the loc of sprite 5 = point (50, 200)
        I mention the other forms so that you will understand examples that make use of
        them, although I find these equivalent expressions harder to decipher:
                put 5 into x
                set x to char 1 to 5 of "hello there"
                put TRUE into the soundEnabled
                set the loc of sprite 5 to point (50, 200)
        You must use the put...into form when replacing part of a string:
                set x = "helloWorld"
                put "H" into char 1 of x
        These won't work:
                set char 1 of x = "H"
                set field 4 = "Some String"
        But these will work:
                set the text of field 4 = "Some String"

        24 Chapter 1  How Lingo Thinks
                                                       Variables and Properties

put "Some String" into field 4

Common Misconceptions About Variables                                                     How Lingo
                                                                                       Thinks
Some Lingo keywords used to assign variables are also used in other ways. Don't
confuse put...into (which sets a value) with put by itself (which prints the value in
the Message window).

put 5 into x -- assigns the value 5 to the variable x

put x  -- prints the value of x in the message window

-- 5

The keyword to is also used in chunk expressions, such as char 1 to 5 of
someString. In the example below, the first to is used to perform the assignment,
but the second to is used to indicate a range of characters.

      set x to char 1 to 5 of "hello there"

The equals sign (=) is used for both assignment and comparison. Don't confuse
the two uses. In C, the single equals sign is used only for assignment, and the
double equals sign (==) is used for comparison (see the online Chapter 20, Lingo
for C Programmers, downloadable from http://www.zeusprod.com/nutshell/chap-
ters/lingoforc.html).

      set x = 5 -- assigns the value 5 to the variable X
      if (x = 5) then put "Yeah" -- Compares x to the value 5

The equals sign assigns a value to an item; it does not indicate an algebraic
equality. In algebra, the following would be meaningless because something can
never equal one more than itself:

      x=x+1

On the other hand, the following is perfectly legitimate and is used frequently in
programming.

      set x = x + 1

How is this possible? The right side of the expression always uses the current (old)
value for an item. The left side sets the new value for an item. The above example
means "Take the current value of the variable x and add one, and then store the
result back into x again." So:

      set x = 4
      set x = x + 1
      put x
      -- 5

An assignment statement is not an algebraic equation to be solved. Only one item
can appear on the left side of the following assignment statement:

      set x = 5 - y
This is not valid:

      set x + y = 5

Although the two statements above may appear algebraically equivalent, they are
not programmatically equivalent. The first one says "Subtract the value of y from 5,

                                       Variables and Properties 25
Variables and Properties

        and then store the result into the variable x." The second one, however, is trying
        to say "Set x and y so that they add up to 5." This confuses a computer because it
        wouldn't know whether to set x to 4 and y to 1, or x to 3 and y to 2, or one of
        the infinite number of alternatives.

      Variable Types

        A variable's storage class (local, parameter, global, or property) determines its
        initial value, its scope (by whom it can be accessed), and whether it persists
        (retains its value) over time. Don't confuse a variable's storage class, often called
        its type, with the data type of its contents. A variable's data type (integer, string,
        list, etc.) depends solely on the value assigned to it and is independent of its
        storage class. See Chapter 5.

        There are four main storage classes (although parameters are generally treated as
        local variables), each of which is created in a different way.

       Local Variables

        Local variables (or temporary variables) are fleeting; they come into existence
        when they are first assigned a value, and they disappear at the end of the current
        handler. Use local variables for temporary needs that are confined to the current
        handler. To create a local variable, pick an arbitrary name, and assign a value to it.
        Variables such as i, j, and k are commonly used for loops or indices. Variables
        such as x and y are commonly used for coordinates.

        In this example, i and y are local variables (everything else is a reserved Lingo
        keyword).

        Example 1-9: Using Local Variables

         on mouseUp
             set y = the locV of sprite the currentSpriteNum
             repeat with i = 1 to 100
                 set the locV of sprite the currentSpriteNum = y + i
                 updateStage
             end repeat
             put i
             put y
             showLocals

         end

        Local variables are "private" to the handler in which they are used. The showLo-
        cals command must be used from within the handler for which you wish to
        display local variables. Likewise, you cannot use put from the message window to
        display a local variable.

        Local variables are independent of other variables in other handlers that may have
        the same name. Because they cannot be used until they are assigned a value, local
        variables have no default value. Using one before assigning it a value results in a
        "Variable used before assigned a value" error. In this example, x is an uninitialized
        local variable and will cause an error.

        26 Chapter 1  How Lingo Thinks
                                                                                      Variables and Properties   How Lingo
                                                                                                              Thinks
      on mouseUp
          if x = 5 then
              go frame 15
          end if

      end
See "Special Treatment of the First Argument Passed" later in this chapter for an
explanation of why using an undeclared local variable as the first argument to a
function does not generate an error.

Parameters

Parameters are local variables that automatically receive the value(s) of incoming
arguments used in the call to the handler (see "Parameters and Arguments" and
"Generalizing Functions" later in this chapter). Parameters are declared (named)
on the same line as the handler name.

Example 1-10: Using Parameters

on someFunction param1, param2, param3
   -- The && operator assembles the string for output
   put "The three input parameters are" && [LC]
              param1 && param2 && param3

end

someFunction 1, "b", 7.5
-- "The three input parameters are 1 b 7.5

Parameters can assume different values each time a handler is called. A different
copy of the parameters is created each time the handler is called and disappears
when the handler ends. Changes to parameters within a handler generally have no
effect outside that handler, but modifying a Lingo list passed as a parameter will
modify the original list in the calling routine as well. See Chapter 6, Lists for impor-
tant additional details. Don't use the name of a global variable as the name for a
parameter or other local variables. See "Common Errors When Using Variables"
later in this chapter

Global Variables

Global variables (or simply globals) are declared using the global keyword, and
they persist throughout all movies until your Projector quits. They come into exist-
ence when a handler that declares them as global first runs and can be accessed
by any handler that also declares them as global. Global variables can be
displayed in the Message window using showGlobals (the built-in global variable
version always appears in the list of globals).

      showGlobals
      -- Global Variables --
      version = "6.0.2"

Whenever you test or set a variable in the Message window it is treated as a global
variable.

      set anyVariable = 5

                                                                      Variables and Properties 27
Variables and Properties

                showGlobals
                -- Global Variables --
                version = "6.5"
                anyVariable = 5
        Use clearGlobals to reset all global variables to VOID, except for the version global,
        which cannot be cleared. ClearGlobals also clears the actorList of the current
        movie in D6.
                clearGlobals
                showGlobals
                -- Global Variables --
                version = "6.5"
        Globals can be shared by MIAWs and the main movie. Any change to the value of
        a global variable is reflected everywhere it is used. For clarity, name your globals
        starting with a "g." Global variables default to VOID (they have no value until one
        is assigned), but they retain their value even when playback stops or a new movie
        is loaded (unless clearGlobals is called). Shockwave clears global variables if the
        browser issues a Stop() command.
        Globals are necessary when you want a variable to outlive the handler in which it
        is used or to send information between two handlers that are not otherwise
        connected.
        In this example, gOne and gTwo are global variables shared by two handlers.

        Example 1-11: Using Global Variables
         on startMovie

             global gOne, gTwo
             set gOne = "Hello"
             set gTwo = 7
         end

        This handler can be in a different script than startMovie:
                on mouseUp
                    global gOne, gTwo
                    if gTwo = 7 then put gOne
                end

        Lingo globals are declared, by convention, at the top of a handler immediately
        under the handler name; declaring globals in the middle of a handler is allowed
        but discouraged. You can declare more than one global with the global keyword
        by separating the variables with commas, as shown above. You can instead use a
        new line for each global declaration, such as:

                global gOne
                global gTwo

        28 Chapter 1  How Lingo Thinks
                                                                                      Variables and Properties   How Lingo
                                                                                                              Thinks
            Globals declared outside of a handler (so-called "global" globals) are
            treated as if they were declared within all subsequent handlers
            within the same script.

For example, if the two handlers above are in the same script, the global declara-
tions could be moved outside the handlers themselves and placed at the top of the
script:

      -- These are "global" globals and can be used
      -- by all handlers in this script cast member
      global gOne, gTwo

      on startMovie
            set gOne = "Hello"

          set gTwo = 7
      end

      on mouseUp
          if gTwo = 7 the put gOne

      end

Property Variables
Property variables are declared using the property keyword and persist as long as
the object of which they are a property exists. (See Chapter 12, Behaviors and
Parent Scripts, if you are not familiar with object-oriented programming, or just
ignore this section for now.)

            Property variables are programmer-defined and should not be con-
            fused with the built-in Lingo properties, although both are attributes
            of their respective objects.

Built-in Lingo properties are predefined attributes of built-in objects, such as
sprites and cast members. Property variables are programmer-defined variables
that are used to add attributes to their own objects (namely scripts).
Property variables are instantiated (created) when the parent script or Behavior
that declares them is itself instantiated (either by Director or by the programmer).
For example, when Director encounters a Behavior attached to a sprite in the
Score it instantiates that Behavior and its properties. (This is explained in detail in
Chapter 12. For now, just assume that when a Behavior is encountered in the
Score, Director assigns appropriate values to any property variables that the
Behavior declares.)
Properties can then be accessed by any handler within the same script. Each
instance (use or occurrence) of the parent script or Behavior gets its own copy of
the property variables that are independent of other copies (despite having the

                                                                      Variables and Properties 29
Variables and Properties

        same name), just as all sprites and cast members have independent properties
        named width and height.
        Property variables are declared at the top of the parent script or Behavior before
        the first handler. You can declare multiple property variables, separated by
        commas, using one property statement, or you can use separate property state-
        ments for each property variable. Property variables default to VOID but are
        usually assigned a value in a parent script's new() handler (or in a Behavior's
        getPropertyDescriptionList() handler; see Chapter 12). When a handler inside a
        parent script or Behavior is called, its private copies of those property values are
        used, unlike global variables that are shared among all scripts. For clarity, name
        your properties starting with a "p."

                    Property variables must be declared outside of any handlers in the
                    script, as shown in the example below.

        In this example, pOne and pTwo are property variables shared by the new() and
        showProps handlers, which are both presumed to reside in the same parent script
        cast member named "ParentScript."

        Example 1-12: Using Property Variables
         property pOne, pTwo

         on new me, a, b
             set pOne = a
             set pTwo = b
             return me

         end new

         on showProps me
             put "pOne is" && pOne
             put "pTwo is" && pTwo

         end showProps

        To test it in the Message window, first instantiate the parent script by calling the
        new() handler. When the programmer instantiates a script, he customarily speci-
        fies initial values for the properties by specifying them as arguments to the new()
        handler (although some programmers prefer to assign properties as a separate step
        from instantiating a script). We create one instance using the integer 6 and the
        string "hello," for the properties pOne and pTwo. We then create a second instance
        with different values to be used as pOne and pTwo.

                set instance1 = new (script "ParentScript", 6, "hello")
                set instance2 = new (script "ParentScript", 9, "goodbye")
        We pass an instance created using new() to showProps (either instance1 or
        instance2). That allows showProps to determine the correct properties for each

        30 Chapter 1  How Lingo Thinks
                                                                                      Variables and Properties   How Lingo
                                                                                                              Thinks
instance separately. Note how the results printed by showProps depend on which
instance variable we pass to it.

      showProps (instance1)
      -- "pOne is 6"
      -- "pTwo is hello"
      showProps (instance2)
      -- "pOne is 9"
      -- "pTwo is goodbye"
Note that inside the script that declares them, property variables are accessed by
using their name, as shown in showProps above. Programmer-defined property
variables can also be accessed from outside a script instance using the script
instance and the keyword the, such as:

      put the propertyVariable of scriptInstance
Property variables belonging to scripts can also be accessed by referencing the
script itself rather than an instance of the script, such as:

      put the propertyVariable of (script "myScript")

            Although they can also be accessed using the keyword the, remem-
            ber that property variables are programmer-defined and are not the
            built-in Lingo properties that also happen to start with the keyword
            the.

Continuing the example above, you can access the properties of instance1 and
instance2 without using showProps, instead using:

      put the pOne of instance1
      -- 6
      put the pTwo of instance2
      -- "goodbye"
Note that simply typing put pOne or put the pOne in the Message window would
fail because you must specify the script instance that owns the property. If no
script instance is specified, the property name must be a built-in system property,
such as:

      put the colorDepth
      -- 8
Refer to Chapter 12, especially if this section left you thoroughly confused.

Common Errors When Using Variables

The following are the most common errors of both new and experienced
programmers when using variables.
Using a variable before assigning a value to it:

      Attempting to use a variable that has never been declared or assigned a value
      causes a "Variable used before assigned a value" error, such as:
      set the locV of sprite 1 = y

                                                                      Variables and Properties 31
Variables and Properties

              (This won't fail in the Message window because y will be treated as global
              containing the value VOID, but it will fail from within a script.)

              New local variables must first be assigned a value:

                set y = 5
                set the locV of sprite 1 = y
              Global variables can be declared with the global keyword, without neces-
              sarily being assigned a value (we presume the global was assigned a
              meaningful value elsewhere; if not, it defaults to VOID):

                global gLocForSprite
                set the locV of sprite 1 = gLocForSprite
              In the following statement, Director complains about the undeclared local
              variable y, which we are attempting to use in the expression although it has
              not been previously assigned a value. Director does not complain about the
              new local variable x, to which we are attempting to assign a value. In other
              words, the right side of the equation can use only existing variables, but the
              left side of the equation can be either an existing or a new variable.

        Not knowing which storage class to use for a variable:
              Use property variables for attributes that have a different value for each
              instance of a parent script or Behavior or that must persist for the life of the
              object. Use global variables when a value must outlive the handler, object, or
              movie in which it is used or must be accessible to multiple handlers, objects,
              or movies. Use local variables for values that are used only for convenience
              within the current handler and then discarded, such as indices in a repeat
              loop or interim steps in a mathematical calculation. Use parameters to accept
              inputs that can make a handler more flexible (see "Parameters and Argu-
              ments" later in this chapter).

                set x = y

        Not knowing when to use a variable:
              Most novices use either too many or too few variables. Use variables when-
              ever you want Director to remember something, such as the results of
              calculations, user input, lists of items, or anything that you need more than
              once. Programming is like cooking. You may be able to cook dinner in one
              pot, or you may need two frying pans and a pressure cooker; it depends on
              the recipe and your personal style. This example:

                on mouseDown
                    if the locH of sprite (the currentSpriteNum) > 50 then
                       put the locH of sprite (the currentSpriteNum)
                    end if

                end
              could be rewritten as:

                on mouseDown
                    set myLocH = the locH of sprite (the currentSpriteNum)
                    if myLocH > 50 then
                       put myLocH
                    end if

                end

        32 Chapter 1  How Lingo Thinks
                                                                                      Variables and Properties   How Lingo
                                                                                                              Thinks
      Both examples are equivalent, but the second one is somewhat easier to read
      and maintain because the result of the lengthy expression is stored in myLocH,
      which is then used for comparing and displaying the value.
Using a "stale" value stored in a variable, instead of the current value:
      When you assign a variable, it records a snapshot in time. You must recalcu-
      late values that are expected to change. The following is wrong because y
      never changes after its initial value is assigned:

      set y = the mouseV
      repeat while y > 50

          put "The mouseV is greater than 50"
      end repeat
      Instead, check the current value of the mouseV property repeatedly:

      repeat while the mouseV > 50
            put "The mouseV is greater than 50"

      end repeat
Forgetting the keyword the when using a Lingo property name:

      Why would mouseV cause a "Variable used before assigned a value" error?

      repeat while mouseV > 50
            put "The mouseV is greater than 50"

      end repeat
      Compare the above repeat...while statement to the previous example.
Using clearGlobals carelessly:
      ClearGlobals indiscriminately resets all global variables to VOID. (In D6, it also
      sets the actorList to [].) This will make any Lingo code that relies on global
      variables or the actorList lose whatever it had stored in them. This is usually a
      very bad thing, and it can be hard to track down if you are working with
      multiple programmers or large projects. Set individual globals to VOID to clear
      them separately instead.
Using the same variable name as both a global and local variable:
      The most common error is to declare a variable global in one handler and
      forget to declare it global elsewhere.

      In that case, it is implicitly a separate local variable in the second handler,
      despite having the same name as a global in the first handler, such as shown
      in Example 1-13.

Example 1-13: Common Errors with Global Variables

on initGlobal
   global gMyValue
   set gMyValue = 27

end initGlobal

on readGlobal
 -- This causes a syntax error
   put gMyValue

end

The second routine must also declare gMyValue as a global:

                                                                      Variables and Properties 33
Variables and Properties

         on readGlobal
             global gMyValue
             put gMyValue

         end
        Test it from the Message window:

         initGlobal
         readGlobal

                -- 27
              Here the error is reversed. The programmer forgot to declare gMyValue as a
              global in the first handler.

                on initGlobal
                    -- gMyValue is treated as a local variable.
                   -- Setting it has no effect outside the handler.
                    set gMyValue = 27

                end initGlobal

                on readGlobal
                    global gMyValue
                   -- The global, also named gMyValue, defaults to VOID
                    put gMyValue

                end
              Test it from the Message window:

                initGlobal
                readGlobal
                -- Void
        Using a global incorrectly as a parameter:
              It is acceptable, even common, to pass a global as an argument to a function
              (see "Parameters and Arguments" later in this chapter). In the receiving func-
              tion, however, you must decide whether you intend to modify the global or
              merely use the global's value for a local operation.
              In Example 1-14, gUserTries is a local variable within gameOver(). The global
              of the same name in finishGame will not be incremented.

        Example 1-14: Passing Globals Variables as Parameters

         on finishGame
             global gUserTries
             gameOver (gUserTries)

         end finishGame

         on gameOver gUserTries
             set gUserTries = gUserTries + 1

         end gameOver

              This can be rewritten in one of two ways. Here, gUserTries is declared global
              within gameOver():

                on gameOver
                    global gUserTries
                    set gUserTries = gUserTries + 1

                end gameOver

        34 Chapter 1  How Lingo Thinks
                                                                                      Variables and Properties   How Lingo
                                                                                                              Thinks
      Alternatively, a local variable can be used and passed back to finishGame.
      on finishGame

          global gUserTries
          set gUserTries = gameOver (gUserTries)
      end finishGame

      on gameOver inValue
          return (inValue + 1)

      end gameOver

La Persistencia de la Memoria

Recall that each time a handler is called, any local variables are discarded when
the handler finishes. If you want a variable's value to persist over repeated calls to
a handler, you must declare it as a global or property variable. (See Chapter 12 for
details on property variables that persist for the life of the object that declares
them.)
Example 1-15 counts the number of times that countMe is called. Don't forget to
reset the global as needed, as shown in testCount.

Example 1-15: Persistent Variables

on countMe
   global gCounter
   set gCounter = gCounter + 1
   put "This handler has been called" && gCounter && "time(s)"

end countMe

on testCount
   global gCounter
   set gCounter = 0
   repeat with i = 1 to 10
       countMe
   end repeat

end

testCount
-- This handler has been called 1 time(s)
-- This handler has been called 2 time(s)
-- etc.

Property variables in score scripts (that is, Behaviors) also persist over time (but
you can not use them with castmember scripts):

      property gCounter
      on mouseUp me

          if gCounter > 10 then
              alert "Are you tired of clicking yet"

          else
              set gCounter = gCounter + 1

          end if
        end mouseUp

                                                                      Variables and Properties 35
Variables and Properties

One-Time Initialization

You may wish to perform some initialization once and only once. You can use a
global variable, as shown in Example 1-16, to track whether the initialization has
taken place.

Example 1-16: One-Time Initialization

on startMovie
   global gBeenDone, gUserScore
   -- If the global is VOID, we haven't initialized yet
   if voidP(gBeenDone)
       -- Do initialization here

set gUserScore=0
       -- Set the global flag to indicate its been done
       set gBeenDone = TRUE

   end if
end startMovie

Variable-Related Lingo

Table 1-1 shows the Lingo commands related to variables, including declaration,
assignment, instantiation, and deallocation of various variable types.

Table 1-1: Variable-Related Commands

Keyword                   Usage
ancestor                  Reserved name for declaring an ancestor property. See Chapter 12.
birth()                   Obsolete, previously used to instantiate an object. See new.
clearGlobals              Resets all global variables, except version, to VOID. Also clears the actorList in
                          D6. Don't use this when working with other programmers who rely on global
global gName1 {,          variables or the actorList.
                          Declares one or more global variables.
gName2}
                          Declares the reserved global version.
global version            Allocates a list. See Chapter 6.
list(), [], or [:]        Used to instantiate an XObject. See Chapter 13, Lingo Xtras and XObjects.
mNew                      Used to deallocate an XObject instance. Chapter 13.
mDispose                  Creates a child object or Xtra instance.
new (script, args)
new (xtra "XtraName")     Indicates the value of the nth parameter received by a handler. See the param-
param(n)                  Count.
                          Indicates the number of parameters received by a handler. Use it to check how
the paramCount            many arguments were specified in the function call.

36 Chapter 1  How Lingo Thinks
                                                                             Variables and Properties

Table 1-1: Variable-Related Commands (continued)

Keyword                  Usage                                                                                                          How Lingo
                                                                                                                                     Thinks
property pName1{,        Declares one or more property variables.

pName2}

property ancestor        Declares an ancestor property. See Chapter 12.
put variable             Prints a variable's value in the Message window.1
put value into variable  Assigns a value to a variable. I prefer using the set command.
set variable = value     Assigns a value to a variable. See also put ... into
set variable to value

showLocals               Prints all local variables in the current handler. Must be used from within a
                         handler, not from the Message window.

showGlobals              Prints all global variables in the Message window.

Stop()                   Stops a Shockwave movie from within the browser and clears global variables.

the property {of object} Refers to a built-in Lingo property.

the property of instance Refers to a programmer-defined property variable of a parent script or
                                Behavior.

the property of list     Refers to properties within a property list. See Chapter 6.
version
                         A global variable containing Director's current version. Use the productVersion
                         property to determine the version without declaring a global.

1 Use put from within a handler to display the value of any variable (including local variables) within that handler in the Message
window. Global variables can be tested using the put command in the Message window iitself. Use the alert command to display
the value of variables in a dialog box, especially from within a Projector where the put command has no effect.

Allocation and Scope of Variables

Local variables in Director are allocated implicitly (that is, without your explicit
instruction) when you assign a value to them. Global and property variables are
allocated explicitly using the global and property keywords. The amount of
memory variables require depends on what is stored in them. Local variables are
deallocated automatically when a handler terminates. Properties are deallocated
when the object of which they are a property is disposed.

The main concern is objects that you never dispose and global variables (which
persist indefinitely) that refer to items that require a lot of memory, such as long
lists or strings. Global variables are never truly disposed, but you can reduce the
memory they use by assigning them to zero or VOID. (Avoid using clearGlobals for
this purpose, as it resets all global variables indiscriminately and in D6 it also
clears the actorList.) Objects are disposed by setting all variables that refer to the

                                                               Variables and Properties 37
Lingo's Skeletal Structure

object to zero or VOID. See Chapters 12 and 13. Table 1-2 shows the scope of indi-
vidual variables of the different data storage classes.

Table 1-2: Data Storage Class Scope

Manner in Which Variable Is Declared Variable's Scope

No explicit declaration; variable is   Can be used in current handler, but only after it is assigned a value,
implicitly local                       using set...= or put...into.

Declared as arguments in the handler Implicitly local, but automatically initialized to value of incoming argu-

definition                             ments. Same scope as a local variable. See "Parameters and Argu-

                                       ments."

Assigned a value in Message window     Variables assigned in the Message window are implicitly global. They
                                       must still be declared global within scripts that wish to make use of
                                       them.

Explicitly declared as a global inside a Variable is global only within handler in which it is declared.
handler

Explicitly declared as a global        Variable is global only within handlers in the same script cast member

outside of any handler, at the top of after the point at which it is declared.

a script

Explicitly declared as a property within Not supported.
a handler

Explicitly declared as a property      Property variable is accessible within any handler in the parent script or
outside of a handler, at the top of a  Behavior. Its scope is limited to the current instance of the script.
parent script or Behavior              Outside the script, it can be accessed with the property of scriptIn-
                                       stance.

Explicitly declared as a property within Property variable is accessible within the ancestor script or to any

an ancestor script                     object using that script as an ancestor

Do statement                           Scope is only the current do statement. See "Do Statements," under
                                       "Dynamic Script Creation."

Lingo's Skeletal Structure

This section covers the bones on which you'll hang the flesh of your Lingo
program. A handful of Lingo commands and functions control program structure
and execution. Each line of Lingo is executed in order, unless the Lingo itself
changes the flow. Lingo detours to execute any handler names it encounters, as
shown in detail under "Nested Handlers" in the earlier section, "Handlers and
Scripts." A detour taken to execute another handler is known as a subroutine call
in most languages. Refer to Chapter 1, How Director Works in Director in a
Nutshell regarding the difference between Lingo's program flow and the move-
ment of the Score's playback head.

38 Chapter 1  How Lingo Thinks
                                                                                     Lingo's Skeletal Structure   How Lingo
                                                                                                               Thinks
Comments

Although Lingo tells Director what to do, the Lingo code is ultimately written and
maintained by humans (or programmers, anyway). Lines starting with two
hyphens (--) are comments that Director ignores; they do not increase the execu-
tion time. Adding comments to someone else's code is a great way to make sure
you understand what it does.
I place comments before the code they describe, although some people place
them afterward, which seems patently absurd to me. Comments should give a
preview, not a postmortem.
Always describe the big picture:

      Include comments at the top of your handler to describe its purpose. Describe
      what the handler does and why. Describe the data stored in major variables,
      such as lists, and which global variables the code uses.
Use comments liberally, even when you are the only programmer:
      Your own comments will help you immensely if you have to fix a bug six
      months later, or they'll help the next poor slob who has to maintain your
      code when you take a better job.
Write comments that complement, not simply reiterate, the programming code:
      Your comments should explain what the code is doing at the conceptual
      level, not the syntactical level. A comment such as "Set x to zero" is useless.
      Use informative comments like "Reset the user's game score." Assume that the
      person reading your comments understands Lingo's basic operation. Don't
      document how Lingo itself works; document what your code accomplishes.
"Comment out" temporary changes or tests:

gComments can exist on separate lines or at the end of a line following other
Lingo commands. Anything following a comment character will be ignored until
the next carriage return. Lingo does not have a way to create multiline comments,
as in C, but you can use the continuation character or use more double-hyphens
on subsequent lines.

Example 1-17: Comments

-- This is a Lingo comment on its own line

set x = 1 -- This is a Lingo comment at the end of a line

-- Here's a "commented out" command that is ignored
-- set x = 1

-- To create a multiline comment in Lingo,
-- begin each line with its own comment delimiter

-- This is a multiline comment by virtue of the ,
continuation character at the end of the previous line

-- Beware! The last line is part of the comment
-- by virtue of the continuation character 
set x = 1

                                                                      Lingo's Skeletal Structure 39
Lingo's Skeletal Structure

        This example demonstrates appropriate comments.
                on resetHighScores
                    -- This handler clears the high score chart
                    global gHighScoreList

                    -- Reset the list holding the top scores
                   -- and the winners' names
                    deleteAll gHighScoreList

                    -- Clear the on-screen high score winners chart
                    set the text of field "HighScore" = EMPTY

                    -- Reset the sprites displaying the highest score
                    repeat with i = 12 to 20

                       set the member of sprite i = member "BigZero"
                    end repeat
                end
        To comment or uncomment your code:
              Manually add or delete two hyphens (--) at the beginning of one or more
              lines of code.
              Use the Comment and Uncomment buttons in the Script window's button bar
              (see Figure 3-3) to comment or uncomment the currently highlighted line(s).
              Use Cmd-Shift-> and Cmd-Shift-< (Mac) or Ctrl-Shift-> and Ctrl-
              Shift-< (Windows) to comment or uncomment the currently highlighted
              line(s). (These are available under Director 4's Text menu.) Use the Comment
              and Uncomment options under the context-sensitive pop-up menu in the
              Script Window, Ctrl-click (Mac) or right click (Windows).

                    A good rule of thumb is one comment for every three lines of Lingo
                    code. Use self-explanatory variable, symbol, and handler names to
                    improve your code's readability.

        You can use the Lingo command nothing as a placeholder when you don't want
        to execute any commands. Unfortunately, unlike comments nothing takes time for
        Lingo to "execute."

      Multi-line Code Structures

        Lingo commands generally occupy a single line (that is, they end when a carriage
        return is encountered), but Table 1-3 shows Lingo statements that occupy more
        than one line. Each multi-line command begins with its own special keyword and
        is terminated by some variation of the end keyword. Director automatically indents
        the statements within the body of a multi-line command two additional spaces. If
        the indentation is wrong, something is wrong with your Lingo. The Lingo continu-
        ation character  should only be used to break long lines, not to "join" the
        multiple lines that are part of a multi-line structure itself.

        40 Chapter 1  How Lingo Thinks
                                                                           Lingo's Skeletal Structure

           The multi-line code fragments shown as examples must be incorpo-                                  How Lingo
           rated into a handler for testing; they will not work from the Message                          Thinks
           window.

Table 1-3: Multi-line Code Structures

Structure                                 Usage

                                         Continues Lingo onto next line.

Created with Option-Return (Mac) or Alt-
Enter (Windows)

on handlerName                            Handler declaration.
{parameter1,parameter2,...}
statements
end {handlerName}1

if expression then                        Executes Lingo conditionally depending if expression is TRUE
   statements                             or FALSE. See "If...Then Statements" later in this chapter and
                                          see Chapter 5, Data Types and Expressions.
else if expression then
   statements

else
   statements

end if

case (expression) of                      Executes Lingo when an expression matches one of the speci-
value1:                                   fied values (see "Case Statement" later in this chapter)

   statements
value2, value3:

   statements
otherwise:

   statements
end case

beginRecording                            Score recording.3
   statements

endRecording2

tell                                      Window messaging.4
   statements

end tell

repeat while expression                   Repeats until expression becomes FALSE.
statements
end repeat

repeat with item in list                  Cycles once through all the items in a list.
statements
end repeat

                                                                Lingo's Skeletal Structure 41
Lingo's Skeletal Structure

Table 1-3: Multi-line Code Structures (continued)

Structure                               Usage

repeat with index = start to end Repeats for a range of values increasing by 1.

statements

end repeat

repeat with index = last down to first  Repeats for a range of values decreasing by 1.

statements

end repeat

1 The handlerName following the end keyword is optional. Include it especially when concluding long handlers whose entirety
is not visible in the Script window.
2 Note that endRecording is one word whereas the other end commands are two words.
3 See Chapter 3, The Score and Animation, in Director in a Nutshell.
4 See Chapter 6, The Stage and Movies-in-a-Window, in Director in a Nutshell.

Common Handler Declaration Errors

All handlers start with the keyword on, followed by the handler name, and end
with the keyword end. A script can contain multiple handlers, one after the other.
Always end one handler before beginning the next one. Let Director's auto-inden-
tation be your guide.

Example 1-18: Handler Declarations

This is wrong:
on mouseUp

   statements

on mouseDown
     statements

end
This is right:
on mouseUp

     statements
end mouseUp

on mouseDown
     statements

end mouseDown

Note the optional use of the handler name after the end keyword. This is useful
for making sure that you always have a matching end handlerName statement for
each on handlerName statement. A handler declaration can also include parame-
ters (not shown). Refer to "Parameters and Arguments" later in this chapter.

Common Multi-Line Structure Errors

Always terminate nested multiline structures from the inside out, as with nested
parentheses.

42 Chapter 1  How Lingo Thinks
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Note the incorrect indentation in Example 1-19 caused by the end if incorrectly
Wrongpreceding the end repeat, and note how the multi-line structures incorrectly cross,
rather than nest.
Right
Example 1-19: Nested Multi-Line Structure Errors

                       on mouseUp
                           if the clickOn = 3 then
                              repeat with x = 1 to 7
                                  puppetSprite x, TRUE

                       end if
                       end repeat
                       end

Note the corrected indentation, and see how the multi-line structures nest neatly,
rather than cross.:

                       on mouseUp
                           if the clickOn = 3 then
                              repeat with x = 1 to 7
                                  puppetSprite x, TRUE
                              end repeat
                           end if

                       end

Don't use a continuation character  improperly at the end of a line. Director
automatically knows that the multiline command continues on the next line.
The following is wrong. You should not use the  character in this case:

      repeat with x = 1 to 7 
          puppetSprite x, TRUE

      end repeat
Here is an example of correctly using an  character within the body of a multi-
line code structure to break a long line of Lingo.

      repeat with x = 1 to 7
          set the member of sprite x = 
          member "Pinky and the Brain" of castLib "World Domination"

      end repeat

Conditional Execution

You can have Director execute different Lingo code in response to various condi-
tions. Any non-zero expression (including negative numbers) is considered TRUE,
and only an expression that evaluates to zero is considered FALSE. Refer to
Chapter 5 for details on evaluating comparisons, including compound expres-
sions. (These example multi-line code fragments must be placed in a handler for
testing.)

                                                                         Conditional Execution 43
Conditional Execution

If...Then...Else...End If Decisions

The if statement will execute different Lingo code based on the value of the speci-
fied expression. This allows you to, say, use a single Director movie on both
Macintosh and Windows but branch to different code depending on the playback
platform, as determined by the platform property, such as:

      if (the platform starts "Windows") then
          -- Do Windows-specific stuff here

      else
          -- Do Macintosh-specific stuff here

      end if

The if statement has many possible forms, but I recommend only these. Items
shown in curly braces are optional. Note the correct indentation:

Single-Clause If...Then...End If

if expression          then
   statement1
   statement2

end if

Multiple-Clause If...Then...Else If...Else...End If

The else if and else clauses are optional:

if expression then           then
     statement1

{else if expression
     statement2}

{else
     defaultAction}

end if

For example:

if x = 1 then
   go frame "Slide1"

else if x = 2 then
   go frame "Slide2"

else if x = 3 then
   go frame "Slide3"

else
   go frame "End"

end if

One-Line and Two-Line If Statements

The following forms are theoretically valid, but they often misbehave in Projectors
and within nested if statements, so I don't recommend them:

      if expression then statement1
or

      if expression then statement1
      else statement2

44 Chapter 1  How Lingo Thinks
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The Classic Three-Line If Statement

The one-line and two-line forms of the if statement make it hard to tell if the
indenting is correct even after Director auto-formats your Lingo.

            Where I use the one-line form of if...then in the examples throughout
            the book, I do so only for brevity. The Lingo compiler occasionally
            makes errors when evaluating one-line and two-line if statements.

Use the following three-line form even for simple if statements, especially when
nesting if statements.

      if (expression) then
          statement

      end if
By always using an end if statement, and by always including a carriage return
after the then keyword, Director won't get confused and neither will you. The
auto-indenting will work reliably and it also makes the code easier to read and
debug. See Chapter 3.

Nested Ifs

You can nest if statements to create the desired logic. It is crucial that you use the
three-line if...end if construct, rather than the one-line or two-line form. An end if
always pairs up with the most recent if from the inside out. Let Lingo's auto-inden-
tation be your guide.

      if expression1 then
          if expression2 then
              action1
          else
              action2
          end if

      else
          defaultAction

      end if
Example 1-20 is a typical usage of a nested if statement:

Example 1-20: Nested If Statements

             if field "name" <> EMPTY then
                 -- These five lines of code are a nested "if"
                 if length(field "name") > 10 then
                     alert "Enter only the first ten letters of your name"
                 else -- This "else" pairs with the second "if"
                     alert "Welcome to my nightmare" && field "name"
                 end if --This "end if" pairs with the second "if"

             else -- This "else" pairs with the first "if"
                 alert "Please enter your name in the field"

             end if --This "end if" pairs with the first "if"

                                                                         Conditional Execution 45
Conditional Execution

      Common Errors When Using If Statements

        Although conceptually simple, the if statement consistently confuses new Lingo
        programmers. Avoid the common pitfalls shown in the following examples.

       Omitting the End If or the Then
        There must be one end if for each if statement. Watch for this, especially with
        nested ifs, such as is shown in Example 1-21.

        Example 1-21: Common If Statement Errors
         if x > 5 then

             if x < 7
                 statements

             end if
         -- You are is missing an "end if" here

        If you omit the then keyword, you'll also have problems:
                if x > 5 -- the keyword "then" is missing
                    statements
                end if

       Failure to Use Else If
        Use one if...else if...end if statement instead of a series of if statements.
        The following is inefficient because if x equals 5, it will never equal 6, and vice
        versa:

                if x = 5 then
                    -- Do something

                end if
                if x = 6 then

                      -- Do something different
                end if
        This is more efficient (see also "Case Statements" later in this chapter):
                if x = 5 then

                    -- Do something
                else if x = 6 then

                      -- Do something different
                end if

       Improper Comparison Expressions

        The incorrect order of comparison can lead to the wrong code being executed.
        Some code may never be executed, or code may be executed unintentionally.
        In this example, both if statements will be executed if x equals 5. This may be
        what you want, but it is more likely a logic error:

                if x > 0 then
                    statements

        46 Chapter 1  How Lingo Thinks
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                                                                                                             Thinks
    end if
      if x > 4 then
            statements
      end if

In this erroneous example, the second branch will never be executed because the
first branch is taken in every case where the second condition would be TRUE:

      if x > 0 then
          statements

      else if x > 4 then
            alternative statements (never reached)

      end if
In this corrected example, the second branch will be executed only if x is less
than 4 but greater than 0:

      if x > 4 then
          statements

      else if x > 0 then
            alternative statements

      end if

Nesting If Statement Unnecessarily or Incorrectly

Nested if statements seem to give people fits. Don't use a nested if statement when
an if...then...else if...end if statement will suffice.
The innermost conditional clauses in this example are never executed.

Example 1-22: Nesting If Statements Properly

if x = 3 then
   alert "Executed option 3"
   -- This is never executed; if x is 3, it's not 4
   if x = 4 then
      alert "Executed option 4"
       -- This is never executed; if x is 4, it's not 5
      if x = 5 then
          alert "Executed option 5"
      end if
   end if

end if

The correct construct is:

      if x = 3 then
          alert "Executed option 3"

      else if x = 4 then
          alert "Executed option 4"

else if x = 5 then
   alert "Executed option 5"
      end if

                                                                         Conditional Execution 47
Conditional Execution

       Excess End If Statements

        Use an end if only for each if, not for each else if (sometimes Director won't
        complain, but the results won't be what you wanted). Example 1-23 is wrong.

        Example 1-23: Using End If Improperly

         if x = 3 then
             alert "Executed option 3"

         else if x = 4 then
             alert "Executed option 4"

         else if x = 5 then
             alert "Executed option 5"

         end if
         end if -- This is not needed
         end if -- This is not needed

        Extraneous end ifs can change your logic unintentionally. Contrast the following
        with the earlier nested if example. It will always execute the last alert command
        because it follows the last end if:

                if field "name" <> EMPTY then
                    -- These five lines of code are a nested "if".
                    if length(field "name") > 10 then
                       alert "Enter only the first ten letters"
                    else
                       alert welcome & field "name"
                    end if -- This terminate the inner "if" statement

                end if -- This terminate the outer "if" statement
                -- This will always be executed
                alert "Please enter your name"

       Missing End If Statements

        Each if statement must have a matching end if. Erroneous structures at the end of
        a preceding handler will trickle into the next handler and corrupt the indentation.
        Note the incorrect indentation in the mouseDown handler caused by the missing
        end if in the preceding mouseUp handler:

                on mouseUp
                    if the clickOn = 3 then
                       if rollover(7) then
                           put "Yahoo!"
                       end if
                       put "whatever"
                       -- This is missing an "end if"

                end

         on mouseDown
                put "Hello" -- Note incorrect indentation
                end

        48 Chapter 1  How Lingo Thinks
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Note the corrected indentation of put "Hello" in the mouseDown handler:

    on mouseUp
          if the clickOn = 3 then
              if rollover(7) then
                 put "Yahoo!"
              end if
              put "whatever"
          end if -- That's better!

      end

      on mouseDown
          put "Hello"

      end

Inefficient Use of If Clauses:

Look for ways to reduce the number of if clauses. Here we've modified the
example shown under "Multiple-Clause If...Then...Else If...Else...End If." We've
reduced the number of clauses by using the value of x to construct the name of
the destination marker ("Slide1," "Slide2," or "Slide3").

      if x >= 1 and x <= 3 then
          go frame ("Slide" & x)

      else
          go frame "End"

      end if

Case Statements

The case statement conditionally executes Lingo statements based on the value of
an item. It is often easier to implement than multiple if...then statements, but long
case statements can be slower than the corresponding if...then constructs. Director
executes the statement(s) following the first value that matches the case clause.
The colon after otherwise is optional, and multiple statements can be included
after each value to be matched. Once a match is found and its statements
executed, subsequent values and their statements are ignored, and execution
continues after the end case statement.

      case (item)of
          value1:
              statement
          value2:
              statement
              statement
          value3, value4:
              statement
          otherwise:
              statement

      end case

                                                                         Conditional Execution 49
Conditional Execution

        Example 1-24 shows a case statement and the equivalent if statement.

        Example 1-24: Case Statements

         on keyDown
             case (the key) of
                 RETURN: go frame "done"
                 TAB, BACKSPACE: beep
                 otherwise: pass
             end case

         end keyDown

        The case statement is equivalent to the following if ... then statement:

                on keyDown
                    if (the key = RETURN) then
                       go frame "done"
                    else if (the key = TAB) or (the key = BACKSPACE) then
                       beep
                    else
                       pass
                    end if

                end keyDown

        To use a comparative expression to branch within a case statement, use TRUE in
        the case clause, and enclose the comparative expression in parentheses, such as:

         on keyDown
             case (TRUE) of
                 (the keyCode >= 123 and the keyCode <= 126):
                    -- The user pressed an arrow key
                 statements
                 (the keyCode = 122):
                    -- The user pressed F1
                 statements
                 (the keyCode = 118):
                    -- The user pressed F4
                 statements
                 otherwise:
                    alert "Please press an arrow key, F1 or F4"
             end case

         end keyDown

      Repeat Loops

        Repeat loops repeat any statements within the body of the loop. They are used to
        cycle through a series of items, such as elements in a list, or to repeat an opera-
        tion a specific number of times (they are equivalent to so-called for...next loops
        used in some languages). When the end repeat command is reached, execution
        begins again at the top of the repeat loop until some condition causes the loop to
        terminate. Execution continues at the statement following the end repeat
        command. Use the Debugging window, described in Chapter 3, to examine the
        exact flow of Lingo as Director executes the steps in the repeat loop.

        50 Chapter 1  How Lingo Thinks
                                                                                        Conditional Execution   How Lingo
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Most repeat loops are very fast, even for hundreds or thousands of iterations, but
Director can't do anything else while you are executing a repeat loop, especially in
Shockwave.

            Don't use repeat loops that monopolize Director's attention for more
            than a few seconds.

In Shockwave, you can't check whether an operation completed with netDone()
from within a repeat loop because Director doesn't perform network operations
during a repeat loop. Likewise, Director doesn't update all system properties or
update the Stage automatically during a repeat loop.
The repeat loop has four forms (3 forms of repeat with plus repeat while), as
shown earlier in Table 1-3. The example multi-line code fragments must be placed
in a handler for testing.
The repeat while command repeats as long as an expression is TRUE. If the expres-
sion never becomes FALSE, it will be an infinite loop.

Example 1-25: Repeat Loops
repeat while (the stillDown = TRUE)

   put "The mouse is still down"
end repeat

The repeat with commands loop through a range of values. Although not neces-
sarily apparent, the three forms of the repeat with loop all use an index variable
(counter) that changes automatically each time the loop is executed.
In this example, the index variable (i) starts at the initial value (in this case 1) and
increments each time through the loop until it hits the upper bound (in this case
100). If the initial value is greater than the upper limit, the statement(s) within the
loop are never executed.

      repeat with i = 1 to 100
            put "The next number is" && i

      end repeat
The following is the equivalent repeat while loop to the above repeat with loop.
You can see that repeat with loops are more convenient.

      set i = 1
      repeat while i <= 100

          put "The next number is" && i
          set i = i + 1
      end repeat
The repeat with...down to command repeats for a decreasing range of values. In
this case, the index variable (i) is decremented (not incremented) each time
through the loop.
      repeat with i = 100 down to 1

                                                                         Conditional Execution 51
Conditional Execution

                    put string(i) && "Bottles of beer on the wall..."
                end repeat
        The repeat with...in command cycles once through all the items in a list. (Refer to
        Chapter 6 or ignore this example for now.) Each time through the loop, i is auto-
        matically set to the next item in the list. Use the following to loop through an
        irregular set of numbers:

                set myList = [12, 17, 52, 43]
                repeat with i in myList

                    put "The next item in the list is" && i
                end repeat
        The variable i is not an integer in the previous example; it is actually the contents
        of the next item in the list. The previous example can be simulated with a stan-
        dard repeat with loop, as follows:

                set myList = [12, 17, 52, 43]
                repeat with j = 1 to count (myList)

                    set i = getAt (myList , j)
                    put "Item number:" && j
                    put "The next item in the list is" && i
                end repeat
        In the last example, note that the index variable j is an integer and can be used to
        print a list element's position within the list. You must manually intialize and incre-
        ment an index variable to obtain a similar counter if using a repeat with...in loop,
        such as:

                set myList = [12, 17, 52, 43]
                set j = 1
                repeat with i in myList

                    put "Item number:" && j
                    put "The next item in the list is" && i
                    set j = j + 1
                end repeat

       Altering Loop Execution

        Use next repeat to skip the current iteration of a repeat loop and to continue with
        the next iteration.

                repeat with x = 1 to the number of members
                    if the memberType of member x = 0 then
                       next repeat
                    end if
                    put "Item" && x && "is type" && the memberType of member x

                end repeat
        Use exit repeat to exit the current repeat loop immediately. Program execution
        continues with the statement following the end repeat statement. Exit repeat exits
        only the current (innermost) repeat loop, and it will not exit nested repeat loops.
        Use exit, or abort, or a flag to exit multiple loops, as shown in Example 1-26.

        52 Chapter 1  How Lingo Thinks
                                                                                        Conditional Execution   How Lingo
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(Again, use the Debugging window to examine the exact flow of Lingo as Director
executes the following code.)

Example 1-26: Nested Repeat Loops
on findIt

   global gFoundIt
   set gFoundIt = FALSE
   -- Search for a #shape cost member
   repeat with y = 1 to the number of castLibs

       repeat with x = 1 to the number of members of castLib y
          set thisItem = the memberType of member x of castLib y
          if thisItem = #shape then
              set gFoundIt = member x of castLib y
              exit repeat -- exit the innermost loop
          end if

       end repeat
     -- exit the outermost loop too

       if gFoundIt then
          exit repeat

       end if
   end repeat

   -- Execution continues here after loop
   if gFoundIt then

       put "Found shape cast member at" && gFoundIt
   else

       put "Shape cast member not found."
   end if
end

Manually Controlling the Loop's Counter
Lingo does not precalculate the number of iterations it will perform for a repeat...
with loop. Rather, it reevaluates the expression each time through the loop. In the
following example, we manually increment the index variable (i) to step by two
rather than one. Note that we add only 1 to i, not 2, because Lingo will automati-
cally increment i once each time the loop is executed.

Example 1-27: Customized Repeat Loops
on printEvenNumbers

   repeat with i = 0 to 100
       put i
       set i = i + 1

   end repeat
end printEvenNumbers

                                                                         Conditional Execution 53
Conditional Execution

                    Avoid manually setting the index variable within a repeat loop
                    unless you need to change the number of loop iterations. Setting it
                    incorrectly can lead to an infinite loop.

        After a loop completes, the index normally is one greater than the ending value:
                on testRepeat
                    repeat with i = 1 to 100
                       put i
                    end repeat
                    put "The ending value for i is" && i
                end testRepeat

                testRepeat
                -- 1
                -- 2
                -- <etc.>
                -- 99
                -- 100
                -- "The ending value for i is 101"

       Infinite Loops

        An infinite loop is a repeat loop that will never be exited because the conditional
        expression never turns FALSE. (Apple's street address in Cupertino, California, is
        One Infinite Loop). An infinite loop will appear to hang the computer, and you
        must abort the Projector or halt the movie to stop it.
        The most simple infinite loop is shown in Example 1-28.

        Example 1-28: Infinite Loops
         repeat while TRUE

             -- do something
         end repeat

        Unless you add an exit repeat, Lingo will never exit such a repeat loop:
                startTimer
                repeat while TRUE
                    if the timer > 60 then
                       exit repeat
                    else
                       -- do something
                    end if
                end repeat

        But this would be better written as:
                startTimer
                repeat while the timer <= 60
                    -- do something
                end repeat

        54 Chapter 1  How Lingo Thinks
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It is easy enough to create an infinite loop accidentally. The following will loop
forever, assuming the loop takes less than 60 ticks to execute, because startTimer
is within the repeat loop and keeps resetting the timer.

      startTimer
      repeat while the timer <= 60

          startTimer
          -- do something
      end repeat
The following would lead to an infinite loop as well. The variable x is unintention-
ally set to 5; the programmer did not realize that x is also being used as the loop's
index variable.

      repeat with x = 1 to 10
          put "x" && x
          set x = 5

      end repeat
A loop will also be infinite if some condition you expect to become FALSE
remains TRUE forever. Suppose you are waiting for a sound to start:

      puppetSound "mySound"
      repeat while not soundBusy(1)

          nothing
      end repeat
If the sound never starts (in this case, you need to add updateStage after the
puppetSound command), Director will loop forever because soundBusy(1) will
never become TRUE, so not soundBusy(1) will always remain FALSE.

            Use the Debugger to diagnose infinite loops and similar problems.
            See Chapter 3.

Parameters and Arguments

Imagine you own a calculator with buttons that each perform a single complete
operation--one button adds 5 plus 7, and another button adds 5 plus 8, and so
on. It might be convenient for those limited operations, but the calculator could
rapidly become unwieldy. (Similarly, Chinese pictographs are inconvenient for
computer usage compared to an alphabet from which you can construct any word.
) In reality, each button on a calculator actually represents either an operand, such
as the number 5, or an operation, such as addition, allowing for many possible
combinations with relatively few keys.
At the beginning of this chapter we used the alert command to display the string
"Hello World" in a dialog box. The alert command accepts any text string as an
argument. An argument is analogous to the operands used in the example of a
calculator above, and the alert command is analogous to the addition button that
performs some operation using the argument(s). The words parameters and argu-

                                                                  Parameters and Arguments 55
Parameters and Arguments

        ments are often used interchangeably to indicate inputs that are passed to a
        function on which it can operate. Strictly speaking, an argument is the item speci-
        fied as part of the function call, and a parameter is the same item once it is
        received inside the function.
        Just as the alert command can accept any string for display, we should strive to
        make our custom handlers flexible by using variables to represent values that can
        change. In contrast, using a fixed number, such as 5, or a fixed string, such as
        "Bruce," in your program is called hardcoding a value.

                    Instead of hardcoding specific values into a handler, generalize the
                    function so that it can operate on whatever arguments are passed
                    into it.

        For example, a handler that finds a file should be flexible enough to find any file
        we ask it to find, rather than always looking for a particular hardcoded filename.
        Beginning programmers often create two or more copies of the same handler with
        only minor variations to accomplish nearly identical tasks. Instead, you should
        create a generalized (that is, flexible) version of the handler that accepts argu-
        ments (or parameters) to accommodate the differences. This is shown in detail in
        Example 1-31 and 1-32. Let's start with a discussion of how arguments are passed
        to a function.

      Passing Arguments

        A simple function performs an operation on the argument(s) passed into it. For
        example, let's define an avg() function that averages two numbers.

        Example 1-29: A Handler That Accepts Parameters

         on avg a, b
             return (a+b) / 2.0

         end

        The names avg, a, and b are chosen arbitrarily. Note that there is a space
        between the handler name (avg) and the first parameter (a) but that subsequent
        parameters (such as b) are separated by a comma from the previous parameter.
        The return statement sends the answer back to whoever called the function.
        Without the return statement, the answer avg calculates would never be known!
        (Forgetting to return a result is a very common error. If the result from a custom
        function returns VOID, you probably forgot the return statement).
        Type the handler in Example 1-29 into a movie script, and test it from the Message
        window. The put command prints the result returned by avg().

                put avg (5,8)
                -- 6.5000
        The integers 5 and 8 are arguments that are operated upon by avg(). The argu-
        ments are separated by commas. The parentheses are required to obtain the value

        56 Chapter 1  How Lingo Thinks
                                                                                  Parameters and Arguments   How Lingo
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returned by avg(), but parentheses are optional when calling a command that does
not return a value, such as alert.
The first argument (5) is automatically assigned to the first parameter (a), and the
second argument (8) is assigned to the second parameter (b). In this case, the
order of the parameters does not affect the result, but in most cases the order of
the parameters is crucial. For example, division is not reflexive: 5 divided by 8
would not be the same as 8 divided by 5.

            If the number of arguments does not match the number of parame-
            ters, Director won't complain. It is up to you to ensure that the cor-
            rect number of arguments is specified.

Modify the avg() handler to create newAvg as follows:
      on newAvg a, b
          put "The first parameter, a, equals" && a
          put "The second parameter, b, equals" && b
          set answer = (a+b)/ 2.0
          put "The answer is" && answer
      end

We've added a local variable, arbitrarily named answer, which is convenient for
holding the value that is printed and then returned to the calling program.
Whereas a and b are implicitly assigned to the arguments in the function call,
answer is explicitly assigned a value using set...=.
There is no difference (as far as the newAvg handler can tell) if we pass integer
variables as arguments to newAvg instead of the integer literals 5 and 8. Type each
of these lines in the Message window, pressing RETURN after each:

      set x = 5
      set y = 8
      put x
      newAvg(x, y)
      -- "The first parameter, a, equals 5"
      -- "The second parameter, b, equals 8"
      -- "The answer is 6.500"

We don't need to use the put command because newAvg displays the result itself
using put, rather than returning an answer.

            The parameters within newAvg, namely a and b, are still equated to
            5 and 8, respectively. The values of the arguments x and y, not x
            and y themselves, are passed to newAvg. This is called passing argu-
            ments by value, rather than by reference.

Refer to "Parameter Passing," in Chapter 4 for more details on parameters passed
by reference and to Chapter 6 for how this affects Lingo lists.

                                                                  Parameters and Arguments 57
Parameters and Arguments

      Generalizing Functions

        NewAvg is a generalized handler that can average any two numbers passed into it
        (we'll see later how to make it accept any number of arguments to average).

       Generalized Sprite Handlers

        To perform an operation on a sprite you must refer to the sprite by its channel
        number (or an expression that evaluates to a channel number). For a sprite in
        channel 1, you might use:

                on mouseUp
                    set the foreColor of sprite 1 = random (255)

                end
        A beginner might create another script to attach to a different sprite in channel 2
        as follows:

                on mouseUp
                    set the foreColor of sprite 2 = random (255)

                end
        Not only is this wasteful, but these scripts will fail miserably if you move the
        sprites to a new channel. Thankfully, Lingo provides several system properties that
        can be used to generalize a handler. When a script is attached to a sprite, the
        currentSpriteNum property always indicates the sprite's channel number. There-
        fore, we can replace the two separate scripts with a single sprite script that can be
        attached to any sprite in any channel and that will always work.

        Example 1-30: A Simple Generalized Behavior

         on mouseUp
             set the foreColor of sprite (the currentSpriteNum) = random (255)

         end

        Refer to Chapter 9 for details on the currentSpriteNum, the spriteNum of me, and
        the clickOn properties and how they can be used to generalize handlers for use
        with any sprite.

       Generalizing a Function with Parameters

        The following is a more sophisticated example of a generalized function, but the
        principle is the same (feel free to skip this section if it is confusing). Let's suppose
        you want to check if the file "FOO.TXT" exists.
        You might write the code shown in Example 1-31 (see Chapter 14 for an explana-
        tion of this Lingo and a more robust example).

        Example 1-31: A HardCoded Function

         on doesFooExist
             -- Use the FileIO Xtra to try to open the file FOO.TXT
             set fileObj = new (xtra "FileIO")
             if objectP(fileObj) then
                 openFile (fileObj, "FOO.TXT", 1)

        58 Chapter 1  How Lingo Thinks
                                                                                  Parameters and Arguments   How Lingo
                                                                                                          Thinks
Example 1-31: A HardCoded Function (continued)

       set result = status (fileObj)
       -- A result of 0 indicates success
       if result = 0 then

          alert "FOO.TXT exists!"
       else

          -- Print the error message in the Message window
          put error (fileObj, result)
          alert "FOO.TXT can't be found"
       end if
      -- Clean up after ourselves
       closeFile (fileObj)
       set fileObj = 0
   end if
end doesFooExist

Now suppose you want to check if a different file exists. Most beginners would
duplicate this long block of code, then change the filename in the openFile() func-
tion call from "FOO.TXT" to their new filename.

            Never duplicate near-identical long blocks of code. Your code
            becomes harder to debug--and much harder to change if you do
            find a bug. Always generalize the code into a utility function that
            you can add to your "tool belt" for future use.

Below we've created a generalized function. Note that it accepts a file name as a
parameter. The name that you specify gets substituted automatically for the file-
Name parameter and is used in the openFile command. Note also that it returns
either TRUE (1) or FALSE (0) to indicate whether the file was found. If it couldn't
be found, you may want to return the error code that was obtained from the
FileIO Xtra's status() call. (It is good practice to simply return some result or status
and let the caller decide whether to post an alert message or do something else.)
Beyond that, it is essentially the same handler as shown in Example 1-31. Try to
make your utility code as non-intrusive as possible, and clean up after yourself.
Note that we opened the file in read-only mode to avoid failing if the file was
already open. We also closed the file when done to clean up after ourselves.
Example 1-32 is primarily for illustration. The FileIO Xtra will search in the current
folder if the searchCurrentFolder is TRUE (the default). It will also search the list of
paths, if any, in the searchpaths. It may not work correctly with long filenames
under Windows. Thus Example 1-32 is not completely robust.

Example 1-32: A Generalized FileExists Function

on fileExists fileName
   -- Use the FileIO Xtra to open the specified file
   set fileObj = new (xtra "FileIO")
   if objectP(fileObj) then
       -- Open file with mode = 1 "read-only"
       openFile (fileObj, fileName, 1)

                                                                  Parameters and Arguments 59
Parameters and Arguments

        Example 1-32: A Generalized FileExists Function (continued)

                 set result = status (fileObj)
                 -- A status of 0 indicates success
                 if result = 0 then

                    set found = TRUE
                 else

                    -- Display the error for debugging
                    put error (fileObj, result)
                    set found = FALSE
                 end if
                 closeFile (fileObj)
                 set fileObj = 0
                 -- Return TRUE or FALSE to indicate if the file exists
                 return found
             end if
         end fileExists

        Now we can easily determine if any file exists, such as:

                put fileExists ("FOO.TXT")
                -- 1
                put fileExists ("FOOPLE.TXT")
                -- 0

        Or use it as follows:

                if fileExists ("FOO.TXT") then
                  -- Do whatever I want to with the file...
                    -- such as open and read it

                else
                    alert "The file can't be found"

                end if

      Using a Generalized Function

        Let's revisit the simple newAvg handler. Add the following handler to your movie
        script that already contains the newAvg handler shown earlier.

        Example 1-33: Using Generalized Functions

         on testAvg
             newAvg (5, 3)
             newAvg (8, 2)
             newAvg (4, 4)
             newAvg (7, 1)

         end

        Choose ControlRecompile Script, and then test testAvg from the Message
        window.

        testAvg
        You should see the output of the newAvg function repeated four times.

        Now, type this in the Message window:

        60 Chapter 1  How Lingo Thinks
                                                                                  Parameters and Arguments   How Lingo
                                                                                                          Thinks
      newAvg (5)
What happens and why? What is the value of the second parameter within the
newAvg handler? It defaults to VOID, as do all unspecified parameters, because
only one argument was specified in the function call. What happens if we forget
to specify the fileName when calling our fileExists() function created earlier?
Let's create a simple divide function (in reality you'd just use "/" to divide):

      on divide a, b
          return float(a)/ b

      end

      put divide (5,5)
      -- 1.0000
What happens if we forget to specify the parameter used as the divisor?
      put divide (7) -- This causes an error

Special Treatment of the First Argument Passed

We saw earlier that an error occurs when a local variable is used before it is
assigned a value. Enter the code shown in Example 1-34 in a movie script, and
recompile the script.

Example 1-34: Special Treatment of First Argument to a Function Call
on testFirstArg

   dummyHandler(x)
end testFirstArg

Isn't x an unassigned local variable? Shouldn't it generate a "Variable used before
assigned a value" error message? Before answering that, let's alter testFirstArg and
recompile the script:

      on testFirstArg
          dummyHandler(x, y)

      end testFirstArg
The variable y is also an unassigned local variable. Why does it generate an error
message, if x did not? The answer lies in the unique way that Lingo treats the first
argument to any function call.

            Even though it is an error, Lingo does not complain if the first argu-
            ment to a function call is an undeclared local variable (in this case
            x).

Multiple scripts may contain handlers of the same name. When you call a func-
tion, Lingo must decide which script to look in first. If the first argument to the
function call is a special entity called a script instance (see Chapter 2), Director
runs the handler in that particular script rather than performing its usual search to

                                                                  Parameters and Arguments 61
Parameters and Arguments

        find the right script automatically. Lingo allows anything as the first argument to a
        function call because it does not verify script instances or handler names during
        compilation. (At runtime it will most likely cause an error, though).

                    If the first argument passed to a custom function call is a script
                    instance, Lingo searches only that script instance for the specified
                    handler. Therefore, you can not pass a script instance as the first
                    parameter to a handler in a movie script because Lingo won't look in
                    the movie script!

        Suppose you want to call a movie script's handler from a Behavior, and suppose
        you want to pass in the Behavior's script instance as an argument. Assume that
        this is the Behavior script.

        Example 1-35: Passing a Script Instance as an Argument

         on mouseUp me
             displayInfo (me)

         end

        This is the movie script:

                on displayInfo someScriptIntanceOrObject
                    put the spriteNum of someScriptIntanceOrObject

                end
        What will happen? Director will issue a "Handler not defined" error because it will
        look for the displayInfo handler only in the Behavior script (but it won't find it).
        You can move the displayInfo handler into the Behavior script, in which case it
        will be available only to instances of that Behavior, or you can rewrite the
        example as shown in the code that follows. Note that we add a dummy VOID
        argument as a placeholder for the first argument to the function call, which allows
        our script instance to become the second argument. Because the second argument
        is not afforded any special treatment, Lingo searches the usual hierarchy and finds
        the displayInfo handler in the movie script!
        Rewrite the displayInfo function call as:

                on mouseUp me
                    displayInfo (VOID, me)

                end
        In the displayInfo handler declaration in the movie script we must add a dummy
        parameter to "catch" the first dummy argument:

                on displayInfo dummyParam, someScriptIntanceOrObject
                    -- Use a dummy argument as the first parameter
                   -- to allow an object to be passed as second argument.
                    put the spriteNum of someScriptIntanceOrObject

                end
        A script instance or child object (which can be thought of as the same thing) is
        often intentionally passed as the first argument to force Lingo to look in the

        62 Chapter 1  How Lingo Thinks
                                                                                  Parameters and Arguments   How Lingo
                                                                                                          Thinks
correct script for the correct handler or property variables. See the example of
property variables in the earlier "Variable Types" section and Chapters 12 and 13.

Optional Arguments and Varying Argument Types

Lingo's built-in commands typically complain if you pass the wrong number or
unexpected type of arguments, but some accept arguments of different data types
and/or a variable number of arguments ("variable" is used here to mean "varying,"
not a Lingo variable). For example, the second argument to setaProp() is either a
property name or a property value, depending on whether the first argument is a
property list or linear list. Likewise, the puppetSound command accepts either one
or two arguments, and some arguments to the puppetTransition command are
optional.

You can also design your custom handlers to allow a variable number of parame-
ters or arguments of varying data types. This makes it easier to create generalized
functions rather than multiple, highly similar versions. If you are creating a library
of functions for yourself or others, it also makes those functions more flexible and
easier to use by the calling routine.

Your function will typically require one or more mandatory arguments that should
be placed at the beginning of the parameter list. Optional arguments should be
placed after the required parameters. If the caller specifies fewer arguments than
the number of parameters you are expecting, later parameters will be VOID.

The playSound example that follows accepts the name or number of a sound to
play and an optional sound channel number. If no channel is specified, it plays
the sound in channel 1. Note the use of voidP() to check whether the caller has
specified the requested parameters.

Example 1-36: Function Accepting Varying Arguments

on playSound soundID, chan
   if voidP(soundID) then
       alert "A sound must be specified"
       exit
   end if
   -- Use channel 1 if the caller does not specify a channel
   -- Or specifies an invalid channel
   if voidP(chan) then
       set chan = 1
   else if not integerP(chan) or 
       (integer (chan) < 1 or integer (chan) > 8) then
       put "Channel should be an integer from 1 to 8"
       set chan = 1
   end if
   -- Play the sound
   puppetSound chan, the number of member soundID
   updateStage

end

-- This plays "woof" in channel 1 (the default)
playSound ("woof")

                                                                  Parameters and Arguments 63
Parameters and Arguments

        Example 1-36: Function Accepting Varying Arguments (continued)

         -- This plays "bark" in channel 3
         playSound ("bark", 3)

        Note that we also check whether the channel number passed in is an integer and
        whether it is a valid sound channel number. Our example also accepts either a
        sound cast member's number or its name, just like as built-in puppetSound
        command. We could enhance the error checking to make sure the specified cast
        member is a sound.

        Refer to Example 5-3 in Chapter 5, Coordinates, Alignment and Registration
        Points, in Director in a Nutshell. It accepts parameters in numerous formats and
        includes substantial error checking.

        You can extend the playSound example to create a handler that accepts addi-
        tional optional arguments, but note that the caller cannot pass a value for an
        optional argument unless all preceding arguments have been specified. For
        example, if we wanted to add a flag to playSound indicating whether to wait for
        the sound to play, we could add another optional parameter called waitFlag.

        Example 1-37: Placeholder Arguments

         on playSound soundID, chan, waitFlag
             -- Beginning of handler is the same code as example above
             -- but is omitted here for brevity
             puppetSound chan, the number of member soundID
             updateStage
             -- This will wait if waitFlag is non-zero. It will
             -- not wait if waitFlag is omitted, and therefore VOID
             if waitFlag then
               repeat while soundBusy (chan)
                  nothing
               end repeat
             end if

         end

                    Arguments and parameters are always matched up by position. The
                    first argument in the function is assigned to the first parameter in the
                    handler definition, and so on.

        In this example, if the caller specifies only two arguments, the second argument
        will be used as the second parameter (chan). If the caller wants to specify wait-
        Flag (the third parameter), he or she must specify three arguments, including a
        placeholder for chan.

                -- The second argument is assumed to be the second
                -- parameter and is mistakenly
                -- interpreted as a channel number
                playSound ("bark", TRUE)
                -- Instead, use 1 as a placeholder for the chan parameter
                playSound ("bark", 1, TRUE)

        64 Chapter 1  How Lingo Thinks
                                                                                  Parameters and Arguments   How Lingo
                                                                                                          Thinks
Variable-Length Parameter Lists

In the previous example, some arguments are optional, but the maximum number
of arguments is known. You can also create handlers that accept an unknown
(ostensibly unlimited) number of arguments. The paramCount property and
param() function decipher an unknown number of arguments passed into a
handler. The paramCount indicates the total number of parameters received and
param(n) returns the nth parameter.

Example 1-38: Variable Number of Parameters

on countParams
   put "Total Params:" && the paramCount
   repeat with n = 1 to the paramCount
       -- This statement prints out each parameter's
   -- number and its value by building a fancy string
       put "Param" && n & ":" && param(n)
   end repeat

end countParams

countParams ("Hello", "there", 5)
-- "Total Params: 3"
-- "Param 1: Hello"
-- "Param 2: there"
-- "Param 3: 5"

Note that no parameters are declared in the handler definition of on count-
Params. It will accept any number of parameters, as would be appropriate if we
wanted to, say, average any number of values. If we expected a fixed number of
parameters, we could instead declare some parameters (in this case a, b, and c)
when we define our handler, such as:

      on newCountParams a, b, c
          put "Total Params:" && the paramCount
          put "Param a:" && a
          put "Param b:" && b
          put "Param c:" && c
          put "Param 1:" && param(1)
          put "Param 2:" && param(2)
          put "Param 3:" && param(3)

      end newCountParams

      newCountParams ("Hello", "there", 5)
      -- "Total Params: 3"
      -- "Param a: Hello"
      -- "Param b: there"
      -- "Param c: 5"
      -- "Param 1: Hello"
      -- "Param 2: there"
      -- "Param 3: 5"

We can access the first parameter as either a or param(1). Likewise, we can
access the second parameter as either b or param(2), and so on. That is,
param(1) is always the first parameter, not merely the first unnamed parameter.

                                                                  Parameters and Arguments 65
Parameters and Arguments

        Note that named parameters are easier to work with when you know how many
        to expect, but param() and the paramCount are more flexible. Use any combina-
        tion of the two. Refer to Example 8-6 and 8-7 which use the paramCount and
        param() to take the sum or average of an indeterminate number of arguments.

      Parameter Error Checking

        The playSound example discussed previously ignores extraneous arguments (that
        is, if more arguments are specified than the number of parameters expected), as
        do many Lingo commands. You can always check the paramCount to warn the
        caller if too many or too few arguments are specified, such as:

                if the paramCount > 3 then alert "No more than 3 please"
        or

                if the paramCount <> 4 then alert "Expected 4 params"
        You can also check the type of each argument, as described in detail in Chapter 5:

         if not integerP(param(1)) then
             alert "First parameter must be an integer"
             exit
                end if

        The verifyParams() function shown in Example 1-39 checks whether the param-
        eter(s) passed into a handler are of the expected data type(s). The details are fairly
        complex, but you don't need to understand them at this point.

                    You can often use a handler as a "black box." You don't need to
                    know what happens inside the box; you need to know only what
                    inputs it requires and what outputs it provides.

        Likewise, you may provide handlers to others without supplying details on how
        they work. You need not understand all the magic as long as you trust the wizard
        behind the curtain. This book and its companion, Director in a Nutshell, try to
        dispel some of the mystery about how Director and Lingo work.
        The verifyParams() function shown in Example 1-39 accepts a property list
        containing parameters and their expected data types (it checks only for integers,
        floats, and strings). See Chapter 6 if you don't understand lists, or just skip the
        details for now. VerifyParams() returns TRUE if the number and type of parame-
        ters are correct and FALSE otherwise. You can extend verifyParams() to handle
        more data types or to post an alert dialog instead of printing errors to the Message
        window.

        Example 1-39: Verifying Parameters

         on verifyParams verifyList, numInput
             -- Check the number of parameters vs. the number expected
             set numExpected = count (verifyList)
             if numInput < numExpected then
                 put "Too few parameters. Expected" && numExpected

        66 Chapter 1  How Lingo Thinks
                                                                                  Parameters and Arguments   How Lingo
                                                                                                          Thinks
Example 1-39: Verifying Parameters (continued)

       return FALSE
   else if numInput > numExpected then

       put "Too many parameters. Expected" && numExpected
       return FALSE
   end if
  -- Check each item in the list and its data type
   repeat with x = 1 to count (verifyList)
       set nextItem = getAt (verifyList, x)
       case (getPropAt(verifyList, x)) of

          #integer:
              if not integerP (nextItem) then
                  put "Expected integer for parameter" && x
                  return FALSE
              end if

          #float:
              if not floatP (nextItem) then
                  put "Expected float for parameter" && x
                  return FALSE
              end if

          #string:
              if not stringP (nextItem) then
                  put "Expected string for parameter" && x
                  return FALSE
              end if

          otherwise:
                  put "Unsupported type for parameter" && x
                  return FALSE

       end case
   end repeat
   return TRUE
end verifyParams

You can use verifyParams() to check if your routine is called with the correct
number and type of arguments. This is useful for debugging your own code or for
trapping errors if you distribute your code for others to use. VerifyParams()
expects a property list containing each parameter and its expected data type. The
following verifies whether a is an integer, b is a string, and c is a float. It also
checks whether exactly three parameters have been received.

      on myHandler a, b, c
          -- Make sure that we received the expect parameters
          if not (verifyParams([#integer:a, #string:b, #float:c],[LC]
                   the paramCount)) then
              alert "Something was wrong"
              exit
          end if
          -- Otherwise everything is okay and we can proceed.

      statements
      end myHandler

Test it from the Message window:

      myHandler (12.5, "a", 5.7)
      -- "Expected integer for parameter 1"

                                                                  Parameters and Arguments 67
Parameters and Arguments

                myHandler (12, 6, 5.7)
                -- "Expected string for parameter 2"

                myHandler (5, "a")
                -- "Too few parameters. Expected 3"
        Reader Exercise: Modify Verify Params() to return an error string.
        See also Example 8-4, "Clipping a Value to a Valid Range," in Chapter 8.

      Congratulations!

        Whew! You now have a foundation on which to build a greater understanding of
        Lingo. Even the most complex programs are built with simple components--vari-
        ables, handlers, keywords, repeat loops, and if statements--so don't be
        intimidated. With patience, you can (de)construct very complicated programs.
        Refer to Table 18-1, for a list of all Lingo keywords so that you can distinguish
        them from variables and custom handler names. Look at examples of other
        people's Lingo code. Try to recognize the various pieces of the Lingo puzzle.
        (Remember diagramming sentences in English class, where you picked out the
        verbs, subjects, adjectives, and prepositional phrases?) Which items are variables?
        Which are keywords? Which are parameters? Which items are arbitrarily chosen by
        the programmer, and which are dictated by Lingo's grammar or syntax?

        This single chapter has covered material from both beginner and intermediate
        programming courses that might be spread out over many months. We also
        touched on some very advanced concepts that will serve you well as you read the
        rest of this book. Don't be discouraged if you didn't understand a lot of it, or if
        you skipped the more intimidating parts. Re-visit this chapter frequently, and you'll
        find new treasures each time. It may seem hard to believe now, but when you
        look back on this chapter a year from now, most of the things that confused you
        will seem quite simple.

        Most of this chapter applies to other programming languages you may encounter.
        If Lingo is your first programming language, rest assured that picking up addi-
        tional languages becomes much easier. In Chapter 4 we compare Lingo to C/C++
        so that you can see both the nitty-gritty details of Lingo and how other languages
        may differ.

        Even though this "book work" may seem tedious, it will allow you to breathe new
        life into all your Director projects once you are out in the field. (Don't forget to
        save your test Director movie periodically).

        I leave this chapter with a reminder that I can point you in the right direction and
        even provide a map of the terrain and a steady compass, but you are ultimately
        your own navigator for the journey that lies ahead.

        This exchange took place in the Director support forum:
        Q: What is TRUE?
        A: How about trying, put TRUE?

        Where else but Lingo can you find out what is TRUE with a mere nine keystrokes?

        68 Chapter 1  How Lingo Thinks
         Chapter 6Lists

                           CHAPTER 6

                        Lists

List Basics

There are two major types of Lingo lists--linear lists and property lists. Refer to
Chapter 5, Coordinates, Alignment, and Registration Points, in Director in a
Nutshell for an additional details on rects and points, which are list-style structures
sharing characteristics of both linear and property lists.
Lists (called arrays in most languages) are convenient for storing and retrieving
related data. A list consists of zero or more elements, which can be of any data
type, enclosed in square brackets. Elements are separated by commas.

            Simplify global variable management by using a single global list
            with multiple properties instead of individual global variables.

You do not need to allocate a specific amount of memory or number of elements
for a list. Director handles the housekeeping as elements are added or deleted.
Elements are often referred to by their index (that is, their position in the list).

            The index of the first element's in a list is 1, not 0 as in some other
            languages. Do not use 0 or negative numbers as indices.

Linear Lists

A linear list is a simple comma-delimited list of elements, defined using the list()
function or by enclosing items within square brackets. Each element can be of any

                                                    180
                                                                                                        List BasicsLists

data type. Use list() without any elements, or empty brackets, [ ], to create a zero-
element linear list. Here are some example linear lists:

      set emptyList = [ ]
      set myList1 = [1, 2, 3]
      set myList2 = list (1, 7, #fumble, "Apples", 6.5, "Money")
Don't include brackets within the list() function unless you intend to create a list
within a list.

      put list([1,2,3])
      -- [[1, 2, 3]]

Property Lists

Each element in a property list consists of a property name:property value pair (or
simply a property:value pair), separated by a colon, such as #myProp:7. The value
can be of any data type. The property name is usually a Lingo-style symbol (see
"Symbols" in Chapter 5, Data Types and Expressions) but can be of any data type.

In fact, any alphanumeric characters used as a property name (except quoted
strings) are converted to symbols.

Avoid using a float value as the property name because Director may not prop-
erly retrieve such elements, especially under Windows. Define a property list by
enclosing one or more property:value pairs, separated by commas, within square
brackets. Use a single colon within two brackets, [:], to create a zero-element prop-
erty list. If your keyboard lacks square brackets, see Example 6-1. Here are some
example property lists:

      set emptyPropList = [:]
      set myPropList1 = [#a:1, #b:2, #c:3]
      set myPropList2 = [#name:"apples", #quantity:5]

Note that the property names fruit and calories are assumed to be symbols,
not variables.

      set myPropList3 = [fruit:"bananas", calories:12]
      put myPropList3
      -- [#fruit: "bananas", #calories: 12]
Property:value pairs are always added to or deleted from property lists as a unit.
The deleteAll() command leaves a property list equal to [:] (empty, but still a prop-
erty list).

Rects and Points

Rects and points are covered in detail in Chapter 5 in Director in a Nutshell. Rects
and points are list-like structures that can be manipulated using many of Lingo's
list functions. With some functions, rects and points behave like property lists;
with other functions, they behave like linear lists. Rects and points are not affected
usefully by commands that add or delete elements, and they should be used only
with commands that get and set the value of existing elements. If you insist on
playing Dr. Frankenstein, you can use deleteAt() to create a franken-rect with only

                                                                                       List Basics 181
List Basics

three elements, but count() will always return 4 for rects and 2 for points. See the
"Rect and Point Operations" section later in this chapter.

Creating Lists

Table 6-1 shows the commands for defining lists.
A "vanilla" list contains either linear elements or property:value pairs, not both. A
property list, however, can be a sub-element within a linear list, and vice versa.

Rects and points are defined with parentheses, not square brackets. Linear lists and
property lists can both contain rects and points. A rect can consist of two points.
If your keyboard lacks square brackets, you can still create linear lists with the
list() function. See Example 6-1 to create property lists.

The following utility creates an empty property list that can be populated with
elements using other list commands.

Example 6-1: Creating Property Lists on Keyboards Without Square Brackets

on createPropList
   -- Left bracket is ASCII 91. Right bracket is ASCII 93
   return value(numToChar (91) & ":" & numToChar (93))

end createPropList
First, create the list and then add elements using addProp:
set myPropList = createPropList()
addProp (myPropList, #propA, 5)
put myPropList
-- [#propA: 5]

See also Example 6-27, "Creating a Property List from Two Linear Lists."

Table 6-1: Commands to Define Lists

                                                                   Property Points/

Command         Usage                    Creates            Linear Lists Lists  Rects

[]              Defines a linear list    Linear list        Yes    N/A          N/A
list(elements)  Defines a linear list
                                         Linear list        Yes    Error        N/A

[:]             Defines a property list  Property list N/A         Yes          N/A

point(x, y)     Defines a point          Point              N/A    N/A          Point

rect(l, t, r, b) Defines a rect          Rect               N/A    N/A          Rect

duplicate(list) Creates independent copy of a Same type as Yes     Yes          Yes

                list, sorted if original was original list

                sorted

value(string(list)) Creates independent unsorted Same type as Yes  Yes          Yes

                copy of a list1          original list

1 The list won't be considered "sorted" by Lingo, but the value(string()) function does not change the order of the existing
elements. See "Sorting, Adding, and Changing List Elements" later in this chapter.

182 Chapter 6  Lists
                                                                                                        List BasicsLists

Invalid List Declarations
The following are all invalid uses of lists.
The following causes a "Handler not defined" error because myList is not a prop-
erty list, as required by addProp():

      set myList = [1,2,3]
      addProp myList, #a, 1
The following causes an "Operator expected" error because list() can't create
property lists:
      put list (#a:5, #b:4)
The following causes a "Property list did not start with a property name" error
because the third element includes a property name, but the first two did not:
      set myList = [1,2,#a:4]
The following causes a "Property or value missing" error because the last element
includes a property name but no property value:
      set myList = [#lowell:1, #paul:2, #kenny:3, #sam]
The following causes an "Operator expected" error, even though the last element
includes a colon, because it still lacks a property value:
      set myList = [#lowell:1, #paul:2, #kenny:3, #sam:]

Valid List Declarations

The following are all acceptable ways of initializing lists.
Linear list with various data types:

      set myList = [#a, void, 7.5, 2, "foo"]
Linear list containing property list as the second element:

      set myList = [1, [#a:1, #b:5, #c:3], 6, "foo"]
Property list containing property lists and linear lists as values:

      set myList = [#someList: [#a:1, #b:5], #otherList: [1,2,4]]
Property list containing a rect and a point as values:

      set myList = [#myRect: rect(2,4,8,7), #myPoint: point(1,3)]
If you specify a value but omit the property name for a property list element,
Lingo inserts a property name equal to the element's index. The following is not
recommended, but it will work, as long as the value missing a property name is
not a symbol.

      set myList = [#a:1, "asd", #c:3, 5, 7.5, void]
      put myList
      -- [#a: 1, 2: "asd", #c: 3, 4: 5, 5: 7.5000, 6: Void]
If you add a variable to a list, the variable's current value is added to the list. If the
variable's value changes, the list remains unchanged.
      set x = 5
      set myList = [x]

                                                                                       List Basics 183
List Basics

                set x = 7
                put x
                -- 7
                put myList
                -- [5]
        If you use a non-list variable as a value in a list, the list will include the variable's
        current contents. Even if the variable changes, the list will not. If you try to use a
        variable name as a property name it will be converted to a symbol:

                set myVar = #someSymbol
                set myList = [myVar:1]
                put myList
                -- [#myVar: 1]
        Use the following to convert the symbolic property name (#myVar) in the previous
        example back to the value of the variable myVar:

                put value(string(getPropAt (myList, 1)))
                -- #someSymbol
        This technique can be used to create a list of variable names, rather than a list of
        the values of the variables. In most cases, you are better off simply using a list
        rather than trying to track variables within a list.

      Assigning, Passing, and Duplicating Lists

        Lists can be assigned to any local, global, or property variable. (A property vari-
        able (which is defined using the property keyword) should not be confused with a
        Lingo property (such as the clickLoc), a property list, or a property of a list. Refer
        to "Child Object Properties" later in this chapter and to Chapter 1, How Lingo
        Thinks, and Chapter 12, Behaviors and Parent Scripts.)
        A list variable points to the beginning of the list in memory; it does not contain a
        copy of the entire list. Lists are passed by reference, not by value, allowing for effi-
        cient passing of large lists between handlers.

                    If you assign one list variable to another variable, or pass a list vari-
                    able as an argument to a handler, both entities point to the same list.
                    If either list changes, both change because they point to the same
                    data in memory.

        In Example 6-2, deleting the elements in listA removes them from listB.

        Example 6-2: Two Variables Pointing to a Single List

         set listA = [1,2,3]
         set listB = listA
         put listB
         -- [1, 2, 3]
         deleteAll (listA)
         put listB
         -- []

        184 Chapter 6  Lists
                                                                                                        List BasicsLists

(The deleteAll command used here has worked since Director 4, but it was undoc-
umented until Director 6.)
Use either the duplicate(list) or value(string(list)) function to make an inde-
pendent copy of a list. (Using value() alone has no effect, and the lists remain
linked.)
In Example 6-3, note that changes to listA no longer affect listB.

Example 6-3: Dissociating Two Lists
set listA = [1,2,3]
set listB = duplicate (listA)
deleteAll (listA)
put listA
-- []
put listB
-- [1, 2, 3]

If you pass a list into a handler and modify that list within the handler, the orig-
inal list in the calling routine is modified as well.

Example 6-4: Modifying Lists Passed to a Handler
on listPass

   set myList = [3,2,1]
   put "MyList started as" && myList
   adjustList (myList)
   put "MyList ended up as" && myList
end listPass

on adjustList someList
   sort someList

end adjustList

Note that myList is altered by adjustList():
      listPass
      -- "MyList started as [3, 2, 1]"
      -- "MyList ended up as [1, 2, 3]"

            Don't modify the original list passed into a handler unless that is the
            specific intent, as with the deleteRange() handler in Example 6-15.
            Instead, work on a copy of the list, and return the altered version via
            a return statement.

In Example 6-5, I've modified adjustList() to create a separate list that it returns to
the caller, and I've also modified listPass() to receive the returned list.

Example 6-5: Using a List in a Handler Without Modifying the Original List
on listPass2

   set myList = [3,2,1]

                                                                                       List Basics 185
List Basics

        Example 6-5: Using a List in a Handler Without Modifying the Original List

             put "MyList started as" && myList
             set workList = adjustList2 (myList)
             put "MyList ended up as" && myList
             put "WorkList ended up as" && workList
         end listPass2

         on adjustList2 someList
             set workList = duplicate(someList)
             sort workList
             return workList

         end adjustList2
        Note that myList is not affected by the changes made within adjustList2().
         listPass2
         -- "MyList started as [3, 2, 1]"
         -- "MyList ended up as [3, 2, 1]"
         -- "WorkList ended up as [1, 2, 3]"

      Using Lists to Return Multiple Values from a Handler

        This section assumes that you have read and understood "Parameters and Argu-
        ments" in Chapter 1, How Lingo Thinks. Arguments of most data types are passed
        to handlers by value. If you want to modify a single variable, it is easy to set it to
        the return value of a function, such as:

                set x = power (10, 2)

        But, suppose you wanted to swap the value of two integer variables. You'd need
        to modify them both, but a function can return only one value. This won't work:

                set x = 1
                set y = 2
                swapInts (x, y)

        You can not write a swapInts() function that modifies two variables because it is
        the value of the variables, and not the variables themselves, that are passed to
        swapInts(). In C, you could manually pass the address of the variables (that is,
        pass them by reference) if you wanted to swap two variables. In Lingo you have to
        use a third variable to swap them manually (and you can not use a function to do
        it), such as:

                set temp = x
                set x = y
                set y = temp

        Arguments that are lists or objects, however, are passed by reference. The called
        function receives the list itself, not just a copy of its contents. Therefore, you can
        pass in, and return, a series of arguments as elements within a list.

        Example 6-6: Using Lists to Return Multiple Values from a Handler

         on mouseUp
             set myList = [#low: the mouseH, #high: the left of sprite 5]
             if the low of myList > the high of myList then
                 swapHighLow (myList)

        186 Chapter 6  Lists
                                                                                                        List BasicsLists

Example 6-6: Using Lists to Return Multiple Values from a Handler (continued)
   end if
   put "myList has been swapped:" && myList

end

on swapHighLow inList
   set temp = the low of inList
   set the low of inList = the high of inList
   set the high of inList = temp

end

Example 6-6 is merely for illustration. In practice you would simply sort the list.

Cleaning Up After Lists

Director deallocates the memory used for a list when no variables still point to it. To
deallocate a list and free memory, assign all variables that pointed to the list to 0.

      set myList = 0

            Clear all global lists (and other objects) in MIAWs to allow them to
            be removed from memory.

Multidimensional Arrays

Linear lists are one-dimensional. Property lists are essentially lists of 2 by n
elements. You can create multidimensional arrays using lists within lists. Irv Kalb
discusses his multidimensional array object in the Lingo User's Journal (September
1995 Volume 1, Number 3) (http://www.penworks.com).
This linear list of three property lists might represent a high score chart or student
test scores.

Example 6-7: Creating and Reading Multidimensional Lists
on printHighScores

     set highScores = [ 
         [#name: "Jane", #score: 85, #level: 8], 
         [#name: "Dick", #score: 75, #level: 7], 
         [#name: "Spot", #score: 95, #level: 9]]

   repeat with x in highScores
       put the name of x && "scored" && the score of x

   end repeat
end

printHighScores
-- "Jane scored 85"
-- "Dick scored 75"
-- "Spot scored 95"

                                                                                       List Basics 187
Lingo List Commands

        In the previous example, you could instead use a double repeat loop, extracting
        the data using indices instead of property names. Note the use of the nested
        getAt() statements in the following example:

                repeat with i = 1 to count (highScores)
                    repeat with j = 1 to count (getAt(highScores, i))
                       put getAt(getAt (highScores, i), j)
                    end repeat

                end repeat

        C programmers will notice that Lingo's syntax for accessing list elements is horribly
        verbose.

      Lists as a Database

        Lists operations are much faster than text string manipulation (see Chapter 7,
        Strings). Sort your lists for faster access. Lists are capable of maintaining a data-
        base of several thousand elements. You can use lists to store and manipulate data
        at runtime, and you can use the FileIO Xtra to read the data from or write the data
        to an external text file for permanent storage. Refer to Chapter 14, External Files,
        for details.

        For more extensive database capabilities, consider a third-party Xtra, such as those
        listed in 10, Using Xtras, in Director in a Nutshell (also available at http://www.
        zeusprod.com/nutshell/links.html)

        Keep in mind that Director's Cast is a multimedia database. You can use lists or
        database Xtras to store castmember names but use the Cast itself to store the
        media. For example, you could create a huge database of songs, cross-referenced
        by artist, title, and genre, and then play them from the cast using puppetSound (or
        from external files using sound playFile).

     Lingo List Commands

        The names of Lingo's list-related commands suck. You'll probably leave the
        O'Reilly bookmark (included at the back of this book) planted firmly in this
        chapter. See "Making Sense of List Commands" later in this chapter for hints on
        finding the right list command, or create wrapper scripts that use names that are
        easier to remember but simply call a single Lingo function, such as:

                on getPropByValue myList, value
                    -- Return the value obtained from getOne
                    return getOne (myList, value)

                end
        Refer to Chapter 3, Lingo Coding and Debugging Tips, for details on wrapper
        scripts.

        Some list commands work with both linear lists and property lists, but others work
        exclusively with one or the other. The same list command may behave differently
        or accept different arguments when used with different list types. There are
        multiple commands that have the same effect on certain list types.

        188 Chapter 6  Lists
                                                                                         Lingo List CommandsLists

            Using the wrong type of list, or a non-list, as the first argument to a
            list function will cause the (highly misleading) "Handler not defined"
            error. See Examples 3-21c through 3-21f.

Use listP() or ilk() to check if your variable is the correct type of list. (See
Example 5-3, "Avoiding Evaluation of the Second Clause in a Compound Expres-
sion," under "Boolean Properties and Logical Operators" in Chapter 5 for important
details.) If necessary, initialize the list inside the current handler, or declare it as a
global variable if it is defined elsewhere.
Many list functions do not return a meaningful value. Instead, they modify the list
used as the first argument. You cannot use the following syntax because add()
does not return a list:

      set myList = add([], 7)
Use this instead:

      set myList = []
      add (myList, 7)

Making Sense of List Commands

List commands often use one attribute of an element--its position (index), prop-
erty name (property), or property value (value)--to determine some other
attribute. For example, you can read the property at a certain position or the value
associated with a certain property.
These tips may help you make sense of the list commands:
 The first argument to any list command must always be a valid list. (If not,

      you'll be greeted with a "Handler not defined" error.)
 If a value is required, it is always the last argument in the parameter list (that

      is, specified after the position or property name).
 The "At" commands--addAt(), setAt(), getAt(), deleteAt()--all use an ele-

      ment's position in the list as the second argument.
 Specifying an index less than 1 or greater than the number of elements in the

      list will cause an "Index out of range" error with most, but not all, functions.
      AddAt() and setAt() accept indices beyond the end of the current list, adding
      elements as needed. Check the count() of a list to ensure that your index is in
      range. Some property list functions fail if you specify a nonexistent property
      name, but setaProp() will append the specified property, if necessary.
 Most "Prop" commands--addProp(), setProp(), getProp(), getPropAt()--work
      with property lists but not linear lists.
 The "aProp" commands--getaProp(), setaProp(), deleteProp() (there is no
      deleteaProp)--are intended for property lists but emulate getAt(), setAt(), and
      deleteAt() when used with linear lists.

                                                                        Lingo List Commands 189
Lingo List Commands

         Only the commands that create lists (shown in Table 6-1) return a list as the
              result of the function call. Commands that modify lists do not return a new
              list, but rather modify the list passed as the first argument "in place."

         The "Get" and "Find" commands--getProp(), getAt(), getLast(), getOne(), get-
              Pos(), getProp(), getPropAt(), findPos(), findPosNear()--always return a sin-
              gle datum, such as a position, property, or value. You must use two separate
              commands to retrieve, say, both an element's property and its value.

         Some commands return error codes, whereas others issue alert dialogs if the
              parameters are invalid.

      Sorting, Adding, and Changing List Elements

        Lingo can optionally sort a list using the sort command. Sorting affects the order in
        which subsequent elements are added, and it affects the speed of commands that
        access the list by value (but not by position). The add, findPos(), findPosNear(),
        and getOne() commands work faster with sorted lists. (The findPosNear() func-
        tion is intended for sorted lists and does not work fully with unsorted lists.) A list
        remains sorted unless some command cancels its "sort-edness". I refer to such a
        list as unsorted because Lingo no longer considers it truly sorted although existing
        elements remain ordered. A list's sort-edness affects the speed with which its
        elements accessed and how future elements are added.

       Sort Order

        A sort is always performed in ascending order.

        Linear lists are sorted by value.

        Example 6-8: Sort Order of Linear and Property Lists

         set myList = [1, 7, #fumble, "Apples", 6.5, "Money"]
         sort myList
         put myList
         -- [1, 6.5000, 7, "Apples", #fumble, "Money"]
        Property lists are sorted by property name.
         set myList = [#r:1, #q:7, #g:#fumble, #b:"Apples", 

                  #a:6.5, #c:"Money"]
         sort myList
         put myList
         -- [#a: 6.5000, #b: "Apples", #c: "Money", #g: #fumble, 

                 #q: 7, #r: 1]

        When sorting elements of different types, note that numbers are sorted before
        strings and symbols. Symbols are treated like strings and are sorted alphabetically,
        comingled with strings (although the string "a" will be placed before the symbol
        #a). Refer to Appendix C, Case-Sensitivity, Sort Order, Diacritical Marks, and
        Space-Sensitivity, for details on the exact sort order of strings with varied case,
        strings and symbols with diacritical marks, and non-alphanumeric characters
        (which differ on the Macintosh and Windows).

        190 Chapter 6  Lists
                                                                                         Lingo List CommandsLists

Recursive Sorting

If you sort a list that in turn contains other lists, only the primary list is sorted.
Example 6-9 recursively sorts all sublists (to any number of levels) within a list
using recursion.

Example 6-9: Recursively Sorting Sublists

on recursiveSort inputList
   -- Sort whatever list is passed in. This will be the
   -- top-level list at first, but will be a sublist if
   -- this is called recursively.
   sort inputList
   repeat with thisElement in inputList
       -- If this element is itself a list, keep sorting
       if listP(thisElement) then
          recursiveSort(thisElement)
       end if
   end repeat

end recursiveSort

Example 6-9 modifies the original list passed into the handler. It is left as an exer-
cise to the reader to write a nondestructive version that returns a sorted listed
without modifying the original list used as the input. (Bear in mind that you can't
simply duplicate the list each time the routine is called because it is called recur-
sively and you must work on the same list following the initial call.)
See Example 8-8, "Recursively Counting Elements in a List," in Chapter 8, Math
(and Gambling) for another example of recursion.

Reverse Sorting and Reverse Ordering

For a descending sort, you can either access a sorted list backwards or create a list
that is sorted in reverse order.
This reverseSort() handler uses the reverseList() handler defined in Example 6-11 to
return an inverted, independent copy of the original sorted list. The reverse sort is
a one-time operation; new elements will not be automatically sorted.

Example 6-10: Reverse Sort

on reverseSort inList
   if listP(inList) then
       set newList = duplicate (inList)
       sort newList
       return reverseList (newList)
   else
       alert "Did not receive a valid list"
       return VOID
   end if

end reverseSort

                                                                        Lingo List Commands 191
Lingo List Commands

        You can use this reverseList() handler to reverse unsorted lists as well.

        Example 6-11: Reversing Unsorted Lists

         on reverseList inList
             if not listP(inList) then
                 alert "Did not receive a valid list"
                 return VOID
             end if
             set listCount = count(inList)
             if ilk (inList) = #propList then
             --reverse a property list
                 set newList = [:]
                 repeat with x = listCount down to 1
                    addProp newList, getPropAt (inList, x), [LC]
                          getAt (inList, x)
                 end repeat
             else
             --reverse a linear list
                 set newList = [ ]
                 repeat with x = listCount down to 1
                    add newList, getAt (inList, x)
                 end repeat
             end if
             return newList

         end reverseList

       Sorting and List Performance

        Sorting a list takes negligible time unless the list is very long. Elements are
        retrieved more quickly from sorted lists, but adding elements to a sorted list is
        marginally slower. For short lists you won't notice any performance difference, but
        if you are accessing a large list many times, you should sort the list. If you are
        adding many elements, it is preferable to sort the list once after all (or most)
        elements are added.

        Creating a list is much slower than accessing its elements, so you should initialize
        a list only once. Building a list incrementally is much slower than declaring an
        entire list at once. If the list is fixed, declare it using one of the functions in
        Table 6-1, rather than adding elements manually. Avoid repeatedly initializing a list
        while looping in a frame. Initialize it once in the previous frame, and access it via
        a global declaration instead.

        Windows machines are generally faster than comparable Macintoshes for list
        creation and access, but it is unlikely you will notice the difference unless using
        very large lists.

        Table 6-2 shows some speed comparisons for various operations. All operations
        were performed 10,000 times on a simple linear or property list containing 2750
        elements. Note that getAt() operates at the same speed for sorted and unsorted
        lists because it accesses elements by their position only. GetAt() is marginally
        faster than getaProp(), even for sorted lists. These tests accentuate very minor

        192 Chapter 6  Lists
                                                           Lingo List Commands

absolute differences, so you might not notice any speed differences for small lists
or fewer operations.

Table 6-2: Sorted List versus Unsorted List Speed Comparison

CPU/Speed           getaProp() Unsorted getaProp() Sorted  getAt() Sorted or
Mac 68040 (33 MHz)                                         Unsorted
PPC 601 (66 MHz)    2390 ticks  99 ticks                   74 ticks
PPC 604e (225 MHz)                                         28 ticks
Pentium (166 MHz)   1056 ticks  38 ticks                   6 ticks
                                                           22 ticks
                    250 ticks   10 ticks

                    528 ticks   28 ticks

Adding Elements to Sorted and Unsorted Lists                                             Lists

Once a list is sorted, Lingo inserts new elements in sorted order, when using
add(), addProp(), setProp(), and setaProp(). A list created by duplicate(list) is
sorted if the original list was sorted. A list created using value(string(list)) is not
sorted by default.

The append() and addAt() commands cancel a list's "sort-edness," but existing
elements remain in their previous order. Subsequent elements added with any
command, including add(), are not inserted in sorted order unless the list is
resorted.

Although undocumented, add() can be used with the same syntax as addAt()--
namely add(list, position, value)--which unsorts the list, as would addAt().

There is no addPropAt() command. Properties are added to the end of unsorted
property lists or sorted by property name in sorted property lists.

When using addAt() or add(), if you specify a position beyond the end of the list,
Lingo fills in the intervening items with zeroes.

Example 6-12 creates a 10-element list full of zeroes.

Example 6-12: Populating a List with Zeroes

set myList = [ ]
addAt(myList, 10, 0)
put myList
-- [0, 0, 0, 0, 0, 0, 0, 0, 0, 0]

List Commands That Add and Modify Elements

Table 6-3 shows commands that add, change, and sort elements. None of these
commands return a meaningful value, but rather modify the list passed as the first
argument. Only the setAt() and set the property of list commands work with

                                                           Lingo List Commands 193
Lingo List Commands

rects and points because the number and position of elements in a rect or point
are fixed.

Table 6-3: Commands That Add, Change, and Sort Elements

Command                      Usage                                                     Points/
                                                              Linear Lists Prop Lists Rects

add(list, val)               Inserts value in sorted order or Yes      Error2 Ignored
                             appends value1

addAt(list, index, val)      Inserts value before element at Yes       Error2 Ignored
add(list, index, val)        specified position3

addProp(list, prop, val)     Inserts property:value pair in Error2     Yes      Error2

                             sorted order or appends pair1

append(list, val)            Appends value to list3           Yes      Error2 Ignored

setaProp(propList, prop, val)4 Replaces or inserts1 value by  Yes, by  Yes, by  Yes, by prop
                                                              index5   prop     name4
setaProp(list, index, val)5  property name or position                 name4

setAt(list, index, val)6     Replaces item by position3 Yes            Yes      Yes

setProp(list, prop, value)   Replaces value by property Error2         Yes7     Error8

                             name

set the property of list9    Sets property's value by its prop- Error  Yes      Yes
                             erty name

sort(list)                   Sorts linear list by value or prop- Yes   Yes      Ignored
                             erty list by property

1 Inserts item at end of unsorted list or in sorted order for sorted lists.
2 Causes "Handler not defined" error.
3 Ignores the sort order and cancels sort-edness of list. Inserts item at specified location or appends to list.
4 For property lists, the second argument to setaProp is assumed to be a property name, not an index, even if it is an integer. The
property will be added if it does not exist, as with addProp(). For rects and points, the second argument to setaProp must be one
of the valid rect or point properties, and not an integer (see Table 6-9). SetaProp also accepts a child object instance instead of
a list as the first parameter.
5 For linear lists, setaProp is identical to setAt and requires an integer index as the second argument. Specifying anything else
causes an "Integer Expected" error.
6 For linear lists, if the index is beyond the limit of the list, setAt() will append to the list. For property lists, the index must be
within the limits of the list. Use the index 1 or 2 for points or an index from 1 to 4 for rects.
7 For property lists, setProp causes a "Handler not defined" error if the property does not exist. Use setaProp() instead.
8 setProp always fails for rects and points. Use setaProp instead.
9 Set the property of list causes a "Property not found" error if the property does not exist. For property lists, use setaProp()
instead. For rects and points, use only the valid rect and point properties.

Deleting Elements

Table 6-4 shows the commands that delete elements from a list. Deleting an
element from a property list deletes its property:value pair. These commands
should not be used with, and are generally ignored by, rects and points (using
deleteOne() can corrupt a rect or point).

194 Chapter 6  Lists
                                                                                         Lingo List CommandsLists

            The deleteOne() function is case-sensitive when locating a string
            value to delete. It is not case-sensitive when accessing elements by
            symbol names instead of strings. Also see getOne(), getPos(), and
            Example 6-13.

Note the changing contents of myList in the examples below. In each succeeding
example, myList contains the value from the previous command. DeleteOne()
returns 1 if successful or 0 otherwise.

Example 6-13: Case-Sensitive Deletion of String Values
Define a list with strings of varied case.

set myList = [#a:"banana", #b:"BaNaNa"]
put myList
-- [#a: "banana", #b: "BaNaNa"]

Try to delete an item by matching the string "BANANA" in the list.
      put deleteOne (myList,"BANANA")
      -- 0

The list doesn't change because "BANANA" (all capital letters) doesn't match any
items, so none were deleted.

      put myList
      -- [#a: "banana", #b: "BaNaNa"]
This deletes property #b (not property #a) because the match is case-sensitive:
      put deleteOne (myList,"BaNaNa")
      -- 1
      put myList
      -- [#a: "banana"]
This deletes property #a because the match is again case-sensitive:
      put deleteOne (myList,"banana")
      -- 1
      put myList
      -- [:]
Note that the final list is an empty property list, not an empty linear list.
Example 6-14 demonstrates that symbols are case-insensitive when used with list
functions.

Example 6-14: Case-Insensitive Deletion of Symbolic Values
Define a list with symbols (instead of strings) of varied case.
set myList = [#a:#banana, #b:#BaNaNa]

Note that Director immediately converts symbols with the same name to the same
case:

      put myList
      -- [#a: #banana, #b: #banana]

                                                                        Lingo List Commands 195
Lingo List Commands

Below, property #a is deleted because it is the first property with a symbol value
matching #BaNaNa (regardless of case).

      put deleteOne (myList,#BANANA)
      -- 1
      put myList
      -- [#b: #banana]

Likewise, any case-insensitive match is sufficient to delete property #b:

      put deleteOne (myList,#BANana)
      -- 1
      put myList
      -- [:]

Table 6-4: Commands That Delete List Elements

Command              Usage                        Return Value        Linear Lists  Prop Lists
deleteAll(list)1                                                      Yes           Yes
                     Deletes all elements from a list, leaving 0
deleteAt(list,       list type unchanged                              Yes2          Yes2
index)
deleteOne(list,      Deletes element by position  0
val)
                     Deletes first element with specified 0: failure  Yes           Yes
deleteProp(list,
prop)                value                        1: success

                     Delete first element with specified prop- 0: failure3 Yes2,3   Yes

                     erty name                    1: success

1 The deleteAll command is convenient for deleting all elements without knowing (or changing) a list's type. It has worked since
Director 4 (although it was undocumented until Director 6). See also the custom deleteRange() handler in Example 6-15.
2 Invalid indices cause an "Index out of Range" error. Check the range first.
3 Using deleteProp() with a linear list requires an integer instead of a property, in which case it emulates deleteAt(); deleteProp()
is intended for property lists and always returns 0 for linear lists.

You can check whether deleteOne() and deleteProp() returned TRUE (1) to deter-
mine whether the operation succeeded. Bear in mind that deleteProp() always
returns 0 for linear lists.

When you delete an item in a list, all subsequent items move up one
place (their indices change). Delete items in reverse order from the
list to avoid any problems.

The deleteAt() command deletes only one element at a time and deleteAll() deletes
them all. The deleteRange() handler below deletes a range of elements. It first
ensures that deleteFrom is less than deleteTo, then it deletes elements from the

196 Chapter 6  Lists
                                                                                         Lingo List CommandsLists

highest index down to the lowest. (Reader quiz: What happens if you delete from
the lowest to highest index instead?)

Example 6-15: Deleting a Range of Elements
on deleteRange inList, deleteFrom, deleteTo
 -- Ensure that deleteFrom is less than deleteTo

   if deleteFrom > deleteTo then
       set temp = deleteFrom
       set deleteFrom = deleteTo
       set deleteTo = temp

   end if
   -- Prevents errors from invalid index ranges
   set deleteFrom = max (1, deleteFrom)
   set deleteTo = min (count (inList), deleteTo)
   -- Delete backwards in list
   repeat with x = deleteTo down to deleteFrom

          deleteAt (inList, x)
   end repeat
   return inList
end deleteRange

put deleteRange ([#a, #b, #c, #d, #e, #f], 2, 4)
-- [#a, #e, #f]

There is no built-in deleteLast() function. Use:
      deleteAt (inList, count (inList))

Getting Info About, and Elements from, Lists

Table 6-5 shows commands that provide information about, or extract elements
from, a list.

            GetOne(), getPos(), and findPos() are case-sensitive when searching
            by strings values! They are not case-sensitive when accessing ele-
            ments by symbol names instead of strings.

Note the case of each string and the result of each query in Example 6-16..

Example 6-16: Case-Sensitive Searching of String Values
set myList = ["banana", "Banana"]
put getPos (myList ,"banana")
-- 1
put getPos (myList ,"Banana")
-- 2
put getPos (myList ,"BANANA")
-- 0

                                                                        Lingo List Commands 197
Lingo List Commands

Again, note the case of each string and the result of each query:

      set myList = [#a:"banana", #b:"Banana"]
      put getOne (myList,"banana")
      -- #a
      put getOne (myList,"Banana")
      -- #b
      put getOne (myList,"BANANA")
      -- 0

As in Example 6-14, getOne(), getPos(), and findPos() are case-insensitive when
searching for symbols.

Table 6-5: Commands That Read from Lists

Command              Usage                          Returns          Linear                 Points/
                                                                     Lists      Prop Lists Rects

count(list)          Counts items in list           item count Yes              Yes      Yes

ilk(list),           Determines list's type         See Table 6-6 Yes           Yes      Yes
listP(list), or
ilk(list, #type)

findPos(list,        Finds the position of the first position, or No            Yes      No
prop)1
                     occurrence of property         VOID if not

                                                    found

findPosNear (list, Finds position (from 1 to        position at No              Yes      No
                                                    which property
prop)2               count()+1) at which specified  belongs

                     property name belongs in list

getaProp (list,      Gets value by property name (for value, or VOID Yes, by    Yes, by  Yes, by
prop)3                                                                          prop     prop
                     propLists, rects, and points) or if property not index4,6  name3    name5
getaProp(list,
                     position (for linear lists)    found5
index)4

getAt(list,          Gets value by position         value6           Yes        Yes      Yes

index)

getLast(list)        Gets value of last element     value, or        Yes        Yes      Yes

                                                    VOID if list is

                                                    empty

getOne(list, val)7 Gets first property or position  prop, or posi- Yes7         Yes8     Yes7
                      that matches value            tion, or 0 if not
                                                    found

getPos(list, val) Gets first position that matches position, or 0 if Yes7       Yes      Yes7

                     value                          not found

getProp(list,        Gets value of property         value            Error9     Yes10 Error11
prop)

198 Chapter 6  Lists
                                                                           Lingo List Commands

Table 6-5: Commands That Read from Lists (continued)

                                                        Linear                    Points/
                                                                      Prop Lists Rects
Command          Usage                         Returns  Lists
                                                                      Yes6. Yes6
getPropAt(list,  Gets property name by position property name Error9
index)
                 Determines minimum or         min or max Yes         Yes  Yes
min(list),       maximum value in list12       value
max(list)
                 Gets the value of a property  value    Error         Yes13 Yes13
the property of
list

1 FindPos() is intended for property lists and expects a property as an argument. It does not return useful information for linear        Lists
lists, nor for rects and points, even when used with valid rect and point properties. Use getaProp() for rects and points instead.
2 FindPosNear() is intended for sorted property lists. It returns the position of an exact match or the position at which the speci-
fied property would be inserted were it added to the list. The return value is between 1 and count(list)+1. For unsorted lists, it
returns the position of an exact match; otherwise it returns count(list)+1. For non-property lists, it does not return meaningful
information.
3 For property lists, the second argument to getaProp() is assumed to be a property name, not an index, even if it is an integer.
For rects and points, the second argument to getaProp() must be one of the valid rect or point properties (see Table 6-7). Use of
an integer position causes a "Symbol expected" error.
4 For linear lists, getaProp() is identical to getAt() and requires an integer index as the second argument. Specifying anything else
causes an "Integer Expected" error.
5 If the property is not found within a rect or a point, getaProp() causes a "Property not found" error. If the property is not found
within a property list, getaProp() returns VOID, which is indistinguishable from a property with a value of VOID.
VOID may be returned as an error code:
put getaProp ([#a:1, #b:3, #c:void], #d)

-- Void

VOID may also be returned as a property's value:
put getaProp ([#a:1, #b:3, #c:void], #c)

-- Void
6 Invalid indices cause an "Index out of Range" error. Check range first.
7 For linear lists, rects, and points, getOne() and getPos() are identical and return the position at which the first occurrence of the
value is found or 0 (zero) if it is not found.
8 For property lists, getOne() returns the name of the first property with the specified value. If not found, it returns 0 (zero), which
is indistinguishable from a property named 0, so you shouldn't use 0 as a property name.
Zero may be returned as an error code:
put getOne ([#a:1, #b:3], 7)

-- 0

Zero may also be returned as the matching property's name:
put getOne ([#a:1, 0:3], 3)

-- 0
9 Causes a "Handler not defined" error.
10 For property lists, getProp() causes a "Handler not defined" error if the property does not exist. Use getaProp() instead.
11 getProp() always fails for rects and points. Use getaProp() instead.
12 min() and max() work with all list element types, including strings. (They are case-sensitive; see Appendix C.)
13 Using the property of list causes a "Property not found" error if the property does not exist. For property lists,
use getaProp() instead. For rects and points, use only valid rect and point properties.

Performing Math with Lists

You can use standard math operators (+, -, *, /, and mod) to alter the contents of a
single list as shown in Example 6-17.

                                                        Lingo List Commands 199
Lingo List Commands

        Example 6-17: Math Operations Performed on Entire Lists
         put [1,2,4] * -6
         -- [-6, -12, -24]
         put [1,2,4] - 7
         -- [-6, -5, -3]
         put -[1,2,4]
         -- [-1, -2, -4]
         put [1,2,4] / 2.0
         -- [0.5000, 1.0000, 2.0000]
         put [1,2,4] mod 2
         -- [1, 0, 0]

        You can also perform calculations using two lists as shown in Example 6-17.
        The resulting list is the length of the shorter of the two lists.

        Example 6-18: Math Operations Performed with Two Lists
         put [1,2,4] + [7,8,9,10]
         -- [8, 10, 13]
         put [1,2,4] - [7,9]
         -- [-6, -7]
         put [1,2,4,12,15] * [4,5,6,12]
         -- [4, 10, 24, 144]
         put [10,20,40] / [4,5,6]
         -- [2, 4, 6]
         put [10,20,40] mod [4,5,6]
         -- [2, 0, 4]

        See also Example 8-6, "Summing a List of Values" and other examples in
        Chapter 8.

      Lists in Expressions

        Lingo treats lists within expressions in a somewhat arbitrary, if not capricious,
        manner. Testing is the only way to determine how Lingo will interpret a given
        expression, usually falling into one of these categories:

       The list is treated as a single entity.

        Note that the entire list is converted to a string:
                put string (myList)
                -- "[1, 3, 4]"

        The logical expression is not applied to each element. The list itself is a non-zero
        entity, so the logical not of the list is FALSE.

                put not ([0,2,3])
                -- 0
        The entire list, not just the first element, is compared to the other operand when
        using = or <>, such as:

        200 Chapter 6  Lists
                                                                                         Lingo List CommandsLists

      put ([4,5,6]) <> 4
      -- 1
      put ([4,5,6]) = 4
      -- 0
Contrast this with the inequality operators below.
Lists are compared on an element-by-element basis. Two variables pointing to two
different lists are considered equal if the lists contain identical elements.

      set x = [1, 2, 3]
      set y = [1, 2, 3]
      put x = y
      -- 1

The first element of the list is used in the expression.

In the following example, the comparison is made between the first element of the
list and the right side of the expression:

      put ([4,5,6]) > 3
      -- 1
      put ([4,5,6]) > 5
      -- 0
Contrast this behavior with that of = and <>. Comparisons involving two items,
with <, >, and =, can all be FALSE because of Lingo's differing rules for evaluating
inequalities and equalities.

The operation is invalid or otherwise ignored.

Attempting to use a list in a Boolean expression causes an "Integer expected" error:

      if (myList) then put "foo"
Both of these comparisons are FALSE, so nothing is printed:

      if myList = FALSE then put "It's FALSE"
      if myList = TRUE then put "It's TRUE"
To check the existence of a list, use listP(). One of the following two statements
will cause a message to print:

      if listP(myList) = FALSE then put "It's FALSE"
      if listP(myList) = TRUE then put "It's TRUE"
The float() function is ignored when used with lists:

      put float ([1,2,3])
      -- [1, 2, 3]
A list is a complex data structure that cannot be integer-ized:

      put integer ([9,8,7])
      -- Void
The results returned from various Lingo functions are not always consistent. Note
that a list is an object according to objectP() but not according to ilk():

      put objectP([1,2,3])
      -- 1

                                                                        Lingo List Commands 201
Commands by List Type

                put ilk([1,2,3], #object)
                -- 0

       Non-list Variables in Compound Expressions

        In the following expression, if myList is not a list, the expression count(myList)
        will cause a "Handler not defined" error (you can't use count() on something that
        is not a list).

                if listP(myList) and count(myList) > 5 then
                    -- whatever

                end if

        Use the construct shown in Example 6-19 instead:

        Example 6-19: Preventing Non-list Arguments from Being Passed to List Commands

         if listP(myList) then
             if count(myList) > 5 then
                 -- whatever
             end if

         end if

        See Example 5-3, "Avoiding Evaluation of the Second Clause in a Compound
        Expression," under "Boolean Properties and Logical Operators" in Chapter 5 for
        details on logical expression evaluation.

     Commands by List Type

        The following section details the commands that perform common operations on
        each type of list. Refer to prior tables for functions common to all lists, such as
        min(), max(), and count().

      Determining a List's Type

        You may need to determine a list's type to decide which commands to use with it.
        You can use listP() to determine whether a datum is any of the four possible types
        of lists, and you can use ilk() for more detailed information about a list's type. You
        can use listP() in if...then statements and ilk() in case statements (see Chapter 5
        for a comparison between ilk() and listP()). Two forms of the ilk() command are
        used with lists:
        ilk(variableName)

              This form of ilk() returns a symbol indicating the data type of the item, such
              as #list, #propList, #rect, or #point for the four list types. Note that linear
              lists return #list, not #linearList. There are dozens of possible return values
              when using ilk() with other data types, such as #integer and #float. See
              Table 5-4.
        ilk(variableName, #dataType)
              This form of ilk() returns a Boolean indicating whether the item is of the spec-
              ified data type. Note that ilk(list, #list) returns TRUE for all types of lists
              and is equivalent to listP(list). Use ilk(list, #linearList) to check

        202 Chapter 6  Lists
                                                                       Commands by List Type

      only whether a list is a linear list. There are many symbols against which you
      can check an item's data type, as shown in Table 16-1.
With the exception of #list and #linearList, note that these two forms of ilk()
are equivalent when used with lists:
      if ilk(list) = #dataType then ...
or:
      if ilk(list, #dataType) = TRUE then...
For example, to check if a list is a property list, use either:
      if ilk(list) = #propList then ...
or:
      if ilk(list, #propList) = TRUE then...
Table 6-6 shows the return values of the ilk() function. The second column shows
the symbolic values returned by the ilk(list) form, and the remaining columns
show the Boolean values returned by the ilk(list, #dataType) form.

Table 6-6: Ilk() Return Values

Data Type ilk()                #list1    #linearList #propList #point        #rect

linear list #list              TRUE      TRUE   FALSE  FALSE                 FALSE

property list #propList TRUE             FALSE  TRUE   FALSE                 FALSE

point    #point                TRUE      FALSE  FALSE  TRUE                  FALSE

rect     #rect                 TRUE      FALSE  FALSE  FALSE                 TRUE

Nonlist  other                 FALSE     FALSE  FALSE  FALSE                 FALSE

1 Same results a list().

Linear List Operations                                                                                                  Lists

Table 6-7 details operations for linear lists. You can also use count(), min(),
max(), and duplicate() in the standard ways. Sorted linear lists are sorted by
value.

Table 6-7: Linear List Operations

To Do This                     Use This         Notes
Initialize a linear list
                               [ ], list(), duplicate(), value(string()) The list must be initialized before using any
Determine if list is a linear                                       other list functions.
list
                               if ilk (list, #linearList) or if ilk(list) = Note different symbol names for the two

                               #list            forms of ilk(). ilk(list) never returns

                                                #linearList. See Table 6-6.

                                                       Commands by List Type 203
Commands by List Type

Table 6-7: Linear List Operations (continued)

To Do This                   Use This                                 Notes

Add a value in sorted order add(list, val)                            Adds item to end of unsorted list or in
                                                                      order for sorted list.

Add a value at a specific    addAt(list, index, val), or              Pads missing elements with zeroes. Unsorts
position                     add(list, index, val)1                   sorted lists.

Add a value to the end of the append(list, val), or add(list, Append unsorts a previously sorted list.

list                         val)                                     Add only appends to unsorted lists.

Replace an element by posi- setAt(list, index, val), or               Element is added if it doesn't already exist.
                                                                      Pads missing elements with zero.
tion                         setaProp(list, index, val)

Delete elements by position deleteAll(list), deleteAt(list, Deleting elements changes indices of

or value.                    index), or deleteOne(list, val)2 subsequent elements.

Get the value at a specific  getAt(list, index), or                   getAt() and getaProp() are identical for
position or last position    getaProp(list, index), or                linear lists.
                             getLast(list)
Find the position of a                                                Returns position of first match or zero if no
specific value               getOne(list, val)2 or                    match
                             getPos(list, val)2

Sort items by value          sort(list)                               Commands that append data unsort the
                                                                      list.

1 Undocumented variation of add() function.
2 Case-sensitive

Property List Operations

Table 6-8 details operations for property lists. You can also use count(), min(),
max(), and duplicate() in the standard ways. There is no addPropAt() command.
Properties are added to the end of unsorted property lists or sorted by property
name in sorted property lists.

Table 6-8: Property List Operations

To Do This                   Use This                                 Notes
Initialize a property list   [ :], duplicate(), value(string())
                                                                      The list must be initialized before using any
Determine if list is a property ilk (list, #propList) or ilk(list) =  other list functions.

list                         #propList                                Correct symbol is #propList, not
                                                                      #propertyList. See Table 6-6.
Add a property:value pair    addProp(list, prop, val) or
                             setaProp(list, prop, val)                addProp() adds item to end of unsorted
                                                                      list or in order for sorted list.
                                                                      setaProp() adds the property if it does not
                                                                      already exist.

204 Chapter 6  Lists
                                                                     Commands by List Type

Table 6-8: Property List Operations (continued)

To Do This                   Use This                         Notes

Replace a property's value by setaProp(list, prop, val) or    setaProp() adds the property if it does not
                                                              already exist.
its property name            setProp(list, prop, val)
                                                              setProp() causes error if property does not
                                                              exist.

Replace a property's value by setAt(list, index, val)         setAt() causes error if index is out of range.
position                                                      It does not add elements when used with
                                                              property lists.
Delete elements by position deleteAll(list), deleteAt(list,
                                                              An element's property:value pair is always
or value                     index), deleteOne(list, val)1    deleted as a unit.

Get the value of a specific  getaProp(list, prop), or         If property is missing, getaProp() returns
property                     getProp(list, prop), or put the  VOID, whereas getProp() and put the
                                                              prop of list cause errors.
                             prop of list
                                                              Index must be within range.
Get the name of the property getPropAt(list, index),
at a specific position

Get the value at a specific  getAt(list, index) or getLast(list) Index must be within range.
position or last position.
                             getOne(list, val)1               getOne() is case-sensitive! Returns prop-
Get the first property name  findPosNear(list, prop)1         erty name or zero if not found.
with a specific value
                                                              Works best with sorted lists. See footnote 2
Find the position of the                                      to Table 6-4 for return values.
nearest property name
matching input               findPos(list, prop)1             Returns index number or VOID.

Find the position of a       getPos(list, val)1               Returns index number of first match or zero     Lists
specific property                                             if not found.

Find the position of a
specific value

Sort items by property name sort(list)                        Commands that append data, unsort the
                                                              list.

Sort items by value          Can't be done automatically for  Use a linear list, or sort it manually
                             property lists                   instead.

1 Case-sensitive

Rect and Point Operations

Lingo's list commands interact with rects and points in bizarre ways. Some
commands treat rects and points as linear lists, and others treat them as property
lists.

A point can be thought of as a list of the form point(x, y) = [#locH:x, #locV:y].

                                                              Commands by List Type 205
Commands by List Type

        A rect can be thought of as a list of the form rect(l, t, r, b) = [#left:l, #top:t,
        #right:r, #bottom:b]. A rect can also be specified as rect(point(l, t), point(r, b),
        but it is immediately converted to the rect(l, t, r, b) form.
        The embedded properties of points and rects can be shown with this utility that
        reads the property names from any list.

        Example 6-20: Extracting Unknown Properties from a List
        on readProps listObj

           set objectType = ilk (listObj)
             put "This #" & objectType && "has" && [LC]

                            count (listObj) && "properties"
           repeat with x = 1 to count (listObj)

               set thisProp = getPropAt (listObj, x)
               set thisValue = getaProp (listObj, thisProp)
                 put "#" & thisProp & ":" && thisValue
             end repeat
         end readProps

         readProps(the clickLoc)
         -- "This #point has 2 properties"
         -- "#locH: 114"
         -- "#locV: 83"

         readProps(the rect of the stage)
         -- "This #rect has 4 properties"
         -- "#left: 0"
         -- "#top: 0"
         -- "#right: 160"
         -- "#bottom: 120"

                    The readProps() utility in Example 6-20 can read properties from a
                    child object or Behavior instance, too. See Chapter 12.

        The names #locH and #locV (for points), and #left, #top, #right, #bottom (for rects)
        are generally the only valid property names for use with list commands requiring a
        property name. You can use them as:

                set the locH of myPoint = 17
                set the top of myRect = 52
        Rects also support reading two additional properties; height and width
                put the width of myRect
                set someVar = the height of myRect
        Table 6-9 details the list operations for rects and points. You can also use count(),
        min(), max(), and duplicate() in the standard ways. Note that rects and points are

        206 Chapter 6  Lists
                                                                             Commands by List Type

generally not affected in a useful way by commands that add or delete elements,
but they do work with commands that get and set the value of elements.

Table 6-9: Rect and Point Operations

To Do This                   Use This                          Notes

Define a rect                rect(l, t, r, b), or rect(point(l, Rects always have four elements and

                             r), point(t, b))                  cannot be defined with list(), [ ], or [:].

Define a point               point(x, y),                      Points always have two elements and
                                                               cannot be defined with list(), [ ], or [:].

Determine if list is a rect  ilk(rect) = #rect or ilk (rect,   ilk (rect, #list) returns TRUE.
                             #rect) = TRUE

Determine if list is a point ilk(point) = #point, or ilk (point, ilk (point, #list) returns TRUE.
                             #point) = TRUE

Add a value                  Can't be done. Rects and points   Points always have two elements, and rects
                             ignore the add(), addAt(), and    always have four.
                             append() commands and
                             addProp()causes an error.

Replace a value by property setaProp(rectOrPoint, prop,        Don't use setProp(). It causes errors in all
                                                               cases, even when using "standard" rect
name                         val), or set the prop of          and point properties.

                             rectOrPoint                       Use an index within range. (1-2 for points,
                                                               1-4 for rects).
Replace a value by position setAt(list, index, val)

Delete elements              Can't be done. deleteAll(),       deleteOne() corrupts the point or rect
                             deleteAt(), and deleteProp() are  structure.
                             ignored.

Get the value of a specific getaProp(rectOrPoint, prop) or Don't use getProp(). It causes errors in all         Lists

property (#left, #top, #right, put the prop of rectOrPoint1 cases, even when using "standard" rect

#bottom, #locH, or #locV)1                                     and point properties.

Get the value at a specific getAt(rectOrPoint, index) or Index must be within range.
position, or last position getLast(rectOrPoint)

Find the position of a       The order of properties for rects and Rects are always in the order (#left, #top,
specific property
                             points is fixed.                  #right, #bottom). Points are always in the

                                                               order (#locH, #locV).

Find the position of a       getPos(rectOrPoint, val), or Returns index number of first match or zero
specific value
                             getOne(rectOrPoint, val)          if no match.

Sort items by value or prop- Can't be done for points and rects. Points and rects ignore the sort()

erty name                                                      command.

1 You can also use put the width of rect, and put the height of rect, but you cannot set these properties.

                                                               Commands by List Type 207
List Utilities

      Looping with Lists

        There are two ways to extract each element in a list (see "Repeat Loops"in
        Chapter 1 for an overview of Lingo repeat loops). The following work for both
        linear lists and property lists.
        You can loop for the number of elements returned by count(), using an integer
        index to extract data from the list. This gives you complete control, especially if
        the number of elements in the list is changing. The index variable (i) can also be
        used for other purposes, such as printing out an element's number.

        Example 6-21: Printing Each Element's Position in a List

         on showList someList
             set numElements = count (someList)
             repeat with i = 1 to numElements
                 put "Element number" && i && "is" && getAt(someList, i)
             end repeat

         end showList

        Note that we counted the number of elements only once, rather than every time
        through the loop. If adding or deleting elements within the loop, you must instead
        recalculate the number of elements each time.
        You can also use the repeat with...in syntax, which automatically extracts each
        value from the list.

        Example 6-22: Printing Each Element's Value Only

         on showList2 someList
             repeat with listValue in someList
                 put "The value is" && listValue
             end repeat

         end showList2

        Note in Example 6-22 that listValue is the value of the current element, not an
        index (as was i). See "Repeat Loops" in Chapter 1 for important additional tips for
        working with the repeat with...in command.

     List Utilities

      Randomized Lists

        The following handler creates a nonrepeating random list of n numbers (Refer to
        Chapter 8 for details on the random() function.) The trick is to place the numbers
        1 through n into random locations throughout the list as it is built.

        Example 6-23: Creating a List of Random Numbers

         on randomNumberList n
             -- Initialize an empty list
             set myList = [ ]
             -- Create a list with the requested number of elements

        208 Chapter 6  Lists
                                                                                                       List UtilitiesLists

Example 6-23: Creating a List of Random Numbers (continued)

   repeat with x = 1 to n
    -- Insert the next number in a random place in the list

       addAt (myList, random(x), x)
   end repeat
   return myList
end randomNumberList

put randomNumberList (10)
-- [8, 10, 7, 5, 1, 3, 9, 4, 2, 6]

The following incorrect routine (which you'll often see used) will likely result in
some numbers being repeated in the list. It incorrectly adds random numbers that
may already exist in the list because the random() function may generate the
same number multiple times. See "How Random Is Random?" in Chapter 8 for
details.

Example 6-24: Incorrect (Nonrandom) List Creation

on incorrectRandom n
   -- Initialize an empty list
   set myList = [ ]
   -- Create a list with the requested number of elements
   repeat with x = 1 to n
   -- Add a random number to the list
       add (myList, random(n))
   end repeat
   return myList

end incorrectRandom

put incorrectRandom (10)
-- [9, 1, 6, 4, 4, 10, 2, 3, 9, 4]

This handler returns a randomized version of any linear list or property list,
leaving the original list intact. Note that this randomizes an existing list, which
differs from creating a random list, as shown above.

Example 6-25: Randomizing an Existing List

on randomizeList inList
   -- Exit if a valid list is not passed in
   if not listP(inList) then
       return void
   end if

   -- Initialize any empty list of the correct type
   if ilk (inList, #propList) then

       set outList = [:]
       set propList = TRUE
   else
       set outList = [ ]
       set propList = FALSE
   end if

                                                                                      List Utilities 209
List Utilities

        Example 6-25: Randomizing an Existing List (continued)

             -- Work with a separate copy of the list
             set work = duplicate (inList)
             -- Loop while there are still elements in the list
             repeat while count(work)

                 -- Select an element at random
                 set next = random (count(work))
                 if propList then
                 -- Add the property element to the output list

                    addProp (outList, getPropAt(work, next), 
                                                     getAt (work, next))

                 else
                    -- Add the linear element to the output list
                    add (outList, getAt (work, next))

                 end if
                 -- Delete the element just selected
                 -- so that it can't be used again
                 deleteAt (work, next)
             end repeat

             return outList
         end randomizeList

      Nonrepeating Random Numbers in a Range

        Suppose you want to simulate a game of Bingo. You'll need to generate a nonre-
        peating list of items that are chosen at random from the pool of remaining "game
        pieces."

        One approach is to create a randomized list and then step through it sequentially.
        You can retraverse the list to repeat the "random" pattern.

        An alternate technique is to create a sequential list, but randomly choose an item
        which you then delete from the list. (We'll use this technique in Chapter 8 to simu-
        late a deck of cards.) The latter approach requires us to rebuild the list when it is
        emptied.

        Suppose you want to create a randomized slide show. You may want to reran-
        domize the list of slides each time through and prevent the same slide from being
        shown twice in a row (if the last item from the previous round is the first item
        chosen in the next round). The following handler returns a nonrepeating random
        number from 1 to n. Every number from 1 to n is used once before any number is
        used twice, and the same number is never returned twice in a row. The key is to
        store the last number in a global variable and perform a lookup using getPos() to
        delete it from the newly regenerated list.

        Example 6-26: A Nonrepeating Random Number Generator

         on getUniqueRandomNumber n
             global gList, gLastNumber

             if voidP(gList) then set gList = randomNumberList(n)

        210 Chapter 6  Lists
                                                                                                       List UtilitiesLists

Example 6-26: A Nonrepeating Random Number Generator (continued)

   if count (gList) = 0 then
       -- Recreate the list
       set gList = randomNumberList(n)
       -- Locate and delete the last number from the new list
       set pickIt = getPos (gList, gLastNumber)
       deleteAt (gList, pickIt)

   end if

   -- Pick a random number and delete it from the list
   set pickIt = random (count(gList))
   set gLastNumber = getAt (gList, pickIt)
   deleteAt (gList, pickIt)
   return gLastNumber
end getUniqueRandomNumber

Converting List Types

Example 6-27 creates a linear list from a property list by stripping off the property
names. It also works with rects and points.

Example 6-27: Converting a Property List to a Linear List

on convertToLinearList inList
   set outList = [ ]
   repeat with x in inList
       add outList, x
   end repeat
   return outList

end convertToLinearList

put convertToLinearList ([#fee: 3, #fie: 5, #fo: 6, #fum: 2])
-- [3, 5, 6, 2]

Example 6-28 builds a property list from two linear lists. The first list contains
property names, and the second list contains values. The two lists must be of
equal length.

Example 6-28: Creating a Property List from Two Linear Lists

on linearListToPropList symbolList, valueList
   set outList = [:]

   if not listP (symbolList) or not listP (valueList) then
       alert "This handler requires two lists"
       return VOID

   else
       set elements = count(valueList)
       set symbolCount = count (symbolList)
       if elements <> symbolCount then
          alert "Both lists must have the same length"
          return VOID
       end if

                                                                                      List Utilities 211
Other Lingo Commands That Use Lists

        Example 6-28: Creating a Property List from Two Linear Lists (continued)
             end if

             repeat with n = 1 to elements
                 addProp outList, getAt(symbolList, n), getAt(inList, n)

             end repeat
             return outList
         end linearListToPropList

         linearListToPropList ([#fee, #fie, #fo, #fum], [3,5,6,2])
         put the result
         -- [#fee: 3, #fie: 5, #fo: 6, #fum: 2]

        This example could be modified to use the createPropList() handler from
        Example 6-1. That would allow people lacking square brackets on their keyboards
        to create property lists from two linear lists defined with the list() function.
        Congratulations, you are now a ListMeister as well as a Lingo God!

     Other Lingo Commands That Use Lists

        Many Lingo commands and properties return or require linear lists, property lists,
        rects, and points. Refer to Chapter 5 in Director in a Nutshell for a detailed list of
        commands using rects and points.

      Linear Lists

        The following Lingo commands use true Lingo linear lists (not property lists).
        These can be manipulated like any other Lingo list, although many can be only
        read, not set.

              the alertHook1 (can assign to a list of script instances)
              the actorList (list of objects)
              the castMemberList of member1 (list of members for Custom Cursor Xtra)
              the cuePointNames of member1 (list of strings)
              the cuePointTimes of member1 (list of integers)
              the cursor of sprite (list of one or two 1-bit cast members)
              cursor (list of one or two 1-bit cast members)
              the deskTopRectList (list of rects)
              the scoreSelection (list of lists that has changed format in D6)
              the searchPath (list of strings)
              the searchPaths ( list of strings)
              the selection of castLib (list of lists)
              the windowList (list of windows)
              the scriptInstanceList of sprite1 (list of script instances)

         1 New in D6

        212 Chapter 6  Lists
                                                                    Other Lingo Commands That Use ListsLists

Property Lists

The following Lingo functions use true Lingo property lists (not linear lists). These
lists can be manipulated like any other Lingo list.
These two handlers both return property lists that describe the parameters used in
a Behavior. The author of a Behavior must define these lists in these handlers.
Director asks for them when needed (see Chapter 12).

      on getPropertyDescriptionList (returns list use to create dialog)
      on runPropertyDialog (returns list of custom values for properties)
The UI Helper Xtra included with D6.5 provides a getBehaviorInitializers() func-
tion that returns the property list passed to on runPropertyDialog.
The MUI Dialog Xtra is a veritable orgy of property lists and nested lists. Refer to
Chapter 15, The MUI Dialog Xtra, and to the downloadable Chapter 21, Custom
MUI Dialogs, for details on these commands that use property lists:
      Alert()
      GetItemPropList()
      GetWidgetList()
      GetWindowPropList()
      Initialize()
      ItemUpdate()

Pseudo-Lists

There are several Lingo commands that don't use Lingo lists but use pseudo-lists
that you might confuse with, or wish to convert to, true Lingo lists.

Child Objects Properties

Although child objects are not identical to property lists, they can also contain
properties that can be manipulated like a property list using the count(), getAt(),
getPropAt(), and setaProp() commands. Refer to Chapter 12 for details. The prop-
erties of a child object can be extracted using the readProps() handler in
Example 6-20.

Text Lists and Pick Lists

These commands don't use true Lingo lists but rather use text strings that are list-
like:

      item of, word of, line of, char of chunk expressions (see Chapter 7)
      the labelList (see Example 6-29)
      mMessageList (see Chapter 13)
      xFactoryList (see Chapter 13)
For example, the labelList returns a text string with each marker label name on a
separate line. Such strings can not be used with the list commands but can be
parsed as described under "Text Parsing" in Chapter 7. It is, however, fairly trivial

                                                   Other Lingo Commands That Use Lists 213
Other Lingo Commands That Use Lists

        to convert a text string delimited by carriage returns (as is the labelList) to a true
        Lingo list.

        Example 6-29: Converting a Text String to a Lingo List
         on convertLinesToList textList

             set realList = []
             -- Convert a list from a text string
             -- to a true Lingo list
             repeat with x = 1 to the number of lines in textList

                 add (realList, line x of textList)
             end repeat
             return realList
         end convertLinesToList

        The output below will depend on your labelList:
                put convertLinesToList (the labelList)
                -- ["menu1", "menu2", "New Marker"]

        The generalized handler above can extract lines of text from any string:
                put convertLinesToList ("Oh" & RETURN & "Atlanta")
                -- ["Oh", "Atlanta"]

        Refer to the example under "Text Parsing" in Chapter 7 that parses all types of
        strings, not just those with multiple lines delimited by carriage returns.
        Don't confuse Lingo lists with text lists from which the user can choose an item.
        There is no way for the user to "see" a Lingo list unless its contents are copied to a
        field cast member. Use field cast members themselves for user interaction.
        Refer to Chapter 12, Text and Fields, in Director in a Nutshell.

       Variable-Length Parameter Lists
        Lingo handlers can accept any number of parameters. The Lingo commands
        param() and the paramCount are list-like functions that decipher the parameters
        passed into a handler. The paramCount represents the total number of parame-
        ters, and param(n) returns the nth parameter, analogous to the count() and getAt()
        list functions. Refer to "Parameters and Arguments" in Chapter 1 for a detailed
        discussion of using the paramCount and param() to decipher variable-length
        parameter lists.
        Likewise, the externalParamCount(), externalParamName(), and externalParam-
        Value() functions are used to access a "list" of the parameters specified in the
        HTML tag used to embed a Shockwave movie in an HTML page. Refer to Chapter
        11, Shockwave and the Internet, in Director in a Nutshell for details.

        214 Chapter 6  Lists
         Chapter 9Mouse Events                                                       Mouse Events

                           CHAPTER 9

                  Mouse Events

Mouse Events

Let's explore Director's sometimes counter-intuitive handling of mouse-related
events. (See Chapter 2, Events, Messages, and Scripts, for details on Director's
overall event handling and script creation.) This chapter is about understanding
mouse event processing, not about creating buttons per se. Refer to Chapter 14,
Graphical User Interface Components, in Director in a Nutshell for details on
custom cursors and on creating well-behaved buttons and using the new Custom
Button Editor Xtra. See also Example 4-6. "Manipulating Sprite Properties to Add
Interactivity to a Button" in Chapter 4, CastLibs, Cast Members, and Sprites, in
Director in a Nutshell.
Whenever the mouse button is pressed or released, Director generates mouseUp,
mouseDown, rightMouseUp, or rightMouseDown events. Attach scripts with
matching event handlers to turn the sprite into a clickable button.
Note that for simple linear presentations, the Tempo channel can be used to wait
in a frame for a mouse click (or key press) before advancing the playback head. In
prior versions of Director, the Tempo channel would ignore mouse events while
waiting for time to elapse or for a sound or digital video to play. This limitation
has been removed in Director 6 (although the Tempo channel doesn't work in
Shockwave).

            The new mouseEnter, mouseLeave, and mouseWithin events are sent
            when the cursor enters or leaves a sprite with a corresponding han-
            dler attached (no mouse click is required). Leave the idleHandler-
            Period at its default setting (0) when using these events.

                                                    251
Mouse Events

        Suppose you have two overlapping sprites in channels 1 and 2, as shown in
        Figure 9-1. The top-most sprite in the higher channel (channel 2) with be in the
        foreground, and the sprite in the lower channel (channel 1) will be obscured
        (covered partially by the sprite in channel 2). (If I say that sprite 1 is below sprite
        2, I am referring to their appearance on the Stage, not their relative positions in
        the Score window sprite channels.)

                                                                           Sprite 1
                                                                           Sprite 2 is
                                                                           "mouse-transparent"

                                                     Mouse click passes through
                                                     Sprite 2 to reach Sprite 1

                                                                           Sprite 1
                                                                           Sprite 2 is
                                                                           "mouse-opaque"

                                                     Mouse click stops at Sprite 2

        Figure 9-1: Two overlapping sprites
        Create two rectangular bitmap sprites in the Paint window and overlap them
        partially on Stage, as shown in Figure 9-1. Attach the following sprite script to the
        sprite in channel 1 (not channel 2).
        Example 9-1: Basic Mouse Events
         on mouseUp

             put "MouseUp detected by sprite" && the clickOn
         end
        Set the movie to loop using the Control Panel, then rewind and play the movie. If
        you click on the top-most sprite in channel 2 (which has no script) in the region
        where it overlaps sprite 1, you should see the following in the Message window:

                -- "MouseUp detected by sprite 1"

        252 Chapter 9  Mouse Events
                                                                                                    Mouse EventsMouse Events

Note that the event registers for sprite 1, not sprite 2, because Director generally
ignores sprites that don't have scripts attached. As far as Director is concerned, the
top-most sprite is mouse-transparent (mouse clicks pass right through it).
Now attach the following mouseDown script to the sprite in channel 2.

      on mouseDown
          put "MouseDown detected by sprite" && the clickOn

      end
Rewind and play the movie and click on the top-most sprite again. Notice that the
mouseDown handler in sprite 2 not only intercepted the mouseDown event, it also
prevented the mouseUp event from reaching the obscured sprite behind it in
channel 1.

            Sprites intercept events that occur within their boundary. Use the
            matte ink to respond only to events within the irregular outline of
            the sprite. When other inks are used, the sprite responds to mouse
            events within its entire bounding rectangle.

Mouse-Opaque Sprites

It is important to understand mouse event handling clearly because it is at the
heart of every Director project--and many programmer bugs. Macromedia uses the
term mouse-opaque in the D6.0 ReadMe file to describe sprites that intercept
mouse click events as described previously.

            A sprite that has an on mouseUp, on mouseDown, on rightMouseUp,
            or on rightMouseDown handler attached becomes mouse-opaque and
            prevents all four of those mouse events from passing through to any
            sprites beneath it.

You can think of a mouse-opaque sprite as a sponge that absorbs mouse clicks or
as an umbrella that prevents mouse events from landing on any sprites below. A
mouse-transparent sprite can be thought of as a piece of clear glass that casts no
shadow. It neither detects the events nor prevents them from reaching other
sprites. In Director 5, any script attached to a sprite turned the sprite mouse-
opaque (that is, would prevent underlying sprites from receiving mouse events). In
Director 6, this was changed so that only those four handlers named previously
cause a sprite to become mouse-opaque. This allows sprites to react to new
messages, such as beginSprite, without necessarily being mouse-opaque. To force
a sprite to be mouse-opaque in Director 6, you can attach a dummy script that has
only a comment in it (and no handlers declared), such as:

      -- This dummy script makes the sprite mouse-opaque

                                                                                   Mouse Events 253
Mouse Events

        This makes the sprite mouse-opaque without actually trapping one of the four
        special mouse click events. See text that follows for details on the clickOn, which
        works only for sprites that have a script attached.

                    Mouse-opaque sprites prevent the four mouse click messages only
                    from being sent to other sprites. They don't prevent untrapped
                    mouse events from passing to frame scripts or movie scripts, nor do
                    they prevent other scripts attached to the same sprite from receiving
                    events.

        For example, even if a sprite has a mouseDown handler attached, it prevents only
        mouseDown events from, say, reaching the frame script. Any mouseUp events
        would still reach the frame script (if the latter had a mouseUp handler). See
        Chapter 2 for details on how events are usually passed through the script
        hierarchy.

        If a mouseUp, mouseDown, rightMouseUp, or rightMouseDown handler passes an
        event with the pass command, the event is not forwarded to other sprites. It passes
        first to the sprite's cast script (if any) and then on to the frame script and possibly
        the movie script. You must manually broadcast the mouse click message using
        sendSprite or sendAllSprites for it to reach multiple sprites.

        This discussion of mouse-opaque sprites pertains only to mouse click events.
        Other types of mouse cursor events are discussed next.

      Cursor-Opaque Sprites

        The mouse-opacity of a sprite has no effect on how the new mouseEnter, mouse-
        Leave, and mouseWithin events are handled. I've coined the name cursor-opaque
        sprites to describe Director's special handling of these new events based on the
        cursor position (not mouse clicks). Again, suppose you have two overlapping
        sprites (see Figure 2-1), and the bottom (partially obscured) sprite has mouseEnter,
        mouseLeave, and mouseWithin handlers attached. If the top-most sprite does not
        have one of these three handlers attached, too, it is cursor-transparent and is
        completely ignored by Director in regard to cursor-related events. Thus, if the
        cursor enters the top-most sprite but is still within the obscured sprite's bound-
        aries, the obscured sprite continues to receive mouseWithin messages. MouseEnter
        or mouseLeave messages are not generated as the cursor enters or leaves the over-
        lapping area of the two sprites. It is as if the top-most sprite didn't even exist.

        Now if you add a mouseEnter, mouseLeave, or mouseWithin handler to the top-
        most sprite, it will become cursor-opaque and be "seen" by Director cursor events.
        Rolling into the overlap area will now send mouseWithin events to the top-most
        sprite, not the bottom sprite. Paradoxically, even though the top-most sprite now
        prevents mouseWithin events from reaching the obscured sprite, rolling between
        the two overlapped sprites now generates mouseEnter and mouseLeave events for
        both sprites. The second cursor-opaque sprite acts as a "foil" (in the dramatic
        sense) for the first sprite.

        254 Chapter 9  Mouse Events
                                                                                                    Mouse EventsMouse Events

            A cursor-opaque sprite receives a mouseLeave event when it
            becomes invisible or is moved off-stage.

Custom Buttons created with the Button Editor Xtra ignored mouseEnter, mouse-
Within, and mouseLeave events in D6.0, but this problem was fixed in D6.0.1.

Checking for Mouse Events

The sections below explore the question, "Who am I?". Use them to write general-
ized Behaviors that work regardless of the sprite to which they are attached.

            Director automatically dispatches events to the correct sprite. You
            need not attempt to determine which sprites were clicked from a
            frame script. Instead, attach appropriate mouse event handlers
            directly to the sprites of interest.

Frame scripts that manually check which sprite was clicked are considered
extremely poor style in Director. The following approach should be avoided:

      on exitFrame
          if the clickOn = 1 then
              -- Do action for sprite 1
          else if the clickOn = 2 then
              -- Do action for sprite 2
          end if

      end
Instead, attach, say, on mouseUp handlers to each sprite of interest, as in:

      on mouseUp me
          -- Perform some action for this sprite

      end
See the tip under "Determining Which Sprite Was Rolled Over" regarding the anal-
ogous issue with rollover-related events.

Determining the Current Sprite's Number
In Chapter 1, How Lingo Thinks, we discussed generalizing a handler to make it
more flexible. To reiterate, you should avoid "hardcoding" sprite channel numbers,
such as:

      on mouseUp
          set the foreColor of sprite 2 = random (255)

      end
If possible, you should instead use a system property to determine the sprite's
channel number automatically, so that the script will work for any sprite to which
it is attached, even if you move the sprite to another channel.

                                                                                   Mouse Events 255
Mouse Events

        In the "To Me or Not To Me" section of Chapter 2, we saw how the
        currentSpriteNum and the spriteNum of me always indicate the sprite channel
        number to which the script is currently attached.

        Example 9-2: What's My Sprite Number?
         on mouseUp

             -- Set the current sprite's foreColor to a random color
             set the foreColor of sprite (the currentSpriteNum) = 

                 random (255)
         end

        To use the spriteNum of me property, you must declare me as a parameter
        following the handler name as shown:

                on mouseUp me
                   -- Declare "me" (see above) when using "the spriteNum of me"
                    set the foreColor of sprite (the spriteNum of me) = 
                       random (255)

                end

       Determining Which Sprite Was Clicked
        Use the clickOn property or clickOn() function to determine the last sprite that the
        user clicked.

                    The clickOn. property and clickOn() function ignore sprites without
                    scripts.

        If you click a scriptless sprite, the clickOn will register for the first sprite beneath it
        that has a script attached. If no sprites under the mouse click have scripts, the
        clickOn returns 0, as it does if you click on the Stage.
        From within the mouseUp or mouseDown handler of the sprite that was clicked,
        the clickOn would be the same as the currentSpriteNum. In prior versions of
        Director you will often see Lingo code such as:

                on mouseUp
                    set the foreColor of sprite (the clickOn) = random (255)

                end
        The spriteNum of me and the currentSpriteNum were added in Director 6 because
        sprites receive many new events that do not require mouse clicks. They are useful
        from within beginSprite, endSprite, mouseEnter, mouseLeave, and mouseWithin
        handlers, as well as mouseUp and mouseDown handlers. The SpriteNum of me is
        useful only from within script scripts (where it returns the current sprite's number);
        from within cast scripts (which don't receive the me instance) use the
        CurrentSpriteNum instead. From within frame scripts and movie scripts the current
        SpriteNum and the SpriteNum of me are not meaningful.

        256 Chapter 9  Mouse Events
                                                                                                    Mouse EventsMouse Events

However, the clickOn returns the last sprite clicked even when checked from a
frame script, movie script, or different sprite script. (The clickOn and clickOn() do
not update within a handler. The value returned is that obtained from before the
handler was called.)
The clickLoc property (or clickLoc() function) returns the point where the mouse
was last clicked, relative to the upper left corner of the Stage. The mouse may
have moved since it was clicked, so check the clickLoc rather than the mouseH or
the mouseV. (The clickLoc does not update within a handler. The value returned is
that obtained from before the handler was called.)

Determining Which Sprite Was Rolled Over

Director 6 vastly simplifies rollover detection. Simply attach mouseEnter and
mouseLeave handlers that highlight and unhighlight the button of interest (say, by
swapping and restoring its member of sprite property). In prior versions of
Director, you must use the rollover() function from within a frame script or movie
script.
The rollover property and rollover() function (without any argument) return the
number of the sprite being rolled over (or 0 when rolling over the Stage). The roll-
over(n) function (where n is a sprite number) returns a Boolean value indicating
whether the cursor is over the specified sprite. Theoretically, if the rollover equals
n, then rollover(n) should return TRUE, but the different forms of the rollover
command disagree when the cursor is over the Stage. So rollover(0) is always
FALSE, even though it should theoretically return TRUE when the rollover or roll-
over() returns 0.
Furthermore, the different forms of the rollover command may disagree when
testing the rollover for overlapping or invisible sprites. The rollover returns the
number of the top-most visible sprite. Rollover(n) will return TRUE even if sprite n
is invisible or not the top-most sprite. But the rollover and rollover() forms of the
command ignore invisible sprites. Either refrain from testing rollover(n) on invis-
ible sprites, or move the sprite off-stage instead.
The mouseMember property returns the member of sprite property of the top-most
visible sprite over which the mouse resides. You can check it against the roll-
over(n) value, such as:

      on exitFrame
          if rollover(5) and [LC]
               (the mouseMember = the member of sprite 5) then
              put "We are apparently rolling over sprite 5"
          end if

      end

This code is reliable only if the same cast member is not used for multiple overlap-
ping sprites.

                                                                                   Mouse Events 257
Mouse Events

                    In Director 6, you rarely need to use the rollover property or roll-
                    over() function. Instead use mouseEnter, mouseWithin, and mouse-
                    Leave handlers attached to the sprites of interest to handle rollover
                    conditions, or the Custom Button Xtra to handle button rollover
                    states automatically.

       Invisible Sprites
        In Director 5, only mouse-related events were sent to sprites. In Director 6, sprites
        receive other new events unrelated to the mouse. In Director 5, setting the visible
        of sprite property to FALSE hid the sprite and disabled all of its handlers (which
        were all mouse-related). This was equivalent to muting the sprite's channel in the
        Score window. In Director 6, the visible of sprite property affects only mouse-
        related events for that sprite. The beginSprite, endSprite, prepareFrame, enter-
        Frame, and exitFrame handlers can be disabled only by muting the sprite's
        channel in the Score window. (Muting disables all events for that sprite channel,
        but setting the visible of sprite affects only its visibility and mouse-related events).

      Standard Mouse Events

        In the simplest case, Director generates a mouseDown event when the user
        depresses the mouse button and a mouseUp event when the user releases the
        mouse button. A given script may contain handlers that trap all, some, or no
        mouse events.

                    You should generally trap either mouseUp or mouseDown events
                    (see text that follows for caveats when trapping both events).

        The mouseDown and mouseUp messages may be sent to different sprites possibly
        in different frames if the mouseDown handler moves the playback head. Trapping
        both messages can lead to two different sprites unintentionally responding to a
        single mouse click sequence. During the time between the two events, other
        messages, such as mouseEnter, may be generated. Table 9-1 lists mouse events in
        the order in which they are generated, assuming the simplest case in which a user
        clicks a sprite. In reality, multiple mouseEnter, mouseWithin, and mouseLeave
        events can be generated after the mouseDown event and before the mouseUp
        event. As the user moves the cursor among various sprites, many mouse rollover
        events may be generated without any mouse click events being sent.

        258 Chapter 9  Mouse Events
                                                                                 Mouse Events

         The frequency of mouseEnter, mouseLeave, and mouseWithin events
         depends on the idleHandlerPeriod. Rollover events are unusably
         sluggish if the idleHandlerPeriod. is not set to 0.

The events shown in column 1 of Table 9-1 should not be confused with the prop-
erties in Table 9-5.

Table 9-1: Mouse Click and Roll Events

Event          Generated When or If:                                          Left Right
mouseEnter1    Cursor enters a sprite's outline2                                
mouseWithin1   Cursor is within a sprite's outline2 (sent repeatedly)           

mouseDown      Left mouse button depressed                                    

rightMouseDown Right mouse button depressed                                      

mouseLeave1    Cursor leaves a sprite's outline2                              

mouseUpOutside1,3 Either mouse button released outside a sprite2 after being depressed  
                      inside a sprite

mouseUp        Left mouse button released                                     

rightMouseUp3  Right mouse button released                                       

buttonClicked1,4 Mouse is released (not pressed) over a Custom Button sprite  

1 New in Director 6.0.
2 See the "Cursor-Opaque Sprites" section earlier in this chapter. The mouseEnter, mouseWithin, and mouseLeave events obey
the matte outline of bitmap sprites using the matte ink, but not for QuickDraw shape sprites. For other inks, the outline is the
sprite's bounding box.
3 There is no on rightMouseUpOutside event.
4 The buttonClicked message is sent only if the enabled of member or enabled of sprite property of the custom button is TRUE.
See Chapter 14 in Director in a Nutshell.

Table 9-2 shows how each mouse event is passed through the Lingo messaging
hierarchy. A given event may be handled by a primary event handler, sprite
script(s), cast script, frame script, or movie script. Refer also to the Table 2-7 in
Chapter 2.

         See the discussion of mouse-opaque and cursor-opaque events at
         the beginning of this chapter. Untrapped mouse click events are
         passed onto frame or movie scripts.

                                                                              Mouse Events 259                                    Mouse Events
Mouse Events

Use rollover(), which is a function, not an event, to check for rollovers from within
frame and movie scripts

Table 9-2: Mouse Event Passing

Event/Message Type Message Passing

mouseDown        mouseDownScriptSprite scripts and/or cast scripts of mouse-opaque sprites
                 Frame scriptMovie scripts.

mouseUp1         mouseUpScriptSprite scripts and/or cast scripts of mouse-opaque sprites
                 Frame scriptMovie scripts.

mouseEnter       Sprite scripts and/or cast scripts of cursor-opaque sprites. (See "Cursor-Opaque
mouseLeave       Sprites" earlier in this chapter.) These events are never passed to frame or movie
mouseWithin      scripts.

mouseUpOutside   Sprite scripts and/or cast scripts of sprite that received original mouseDown or right-
                 MouseDown event. See "MouseUpOutside Events" later in this chapter.

rightMouseDown2  Sprite scripts and/or cast scripts of mouse-opaque spritesFrame scriptMovie
rightMouseUp1,2  scripts.

buttonClicked    Sent by Custom Buttons to sprite scripts and/or cast script of clicked sprite only. Not
                 sent to obscured sprites or passed to Frame script or Movie script.

1 The mouseUp and rightMouseUp outside events are sent directly to the frame script, bypassing the sprite and cast scripts, if
they follow a mouseUpOutside event and the buttonStyle property is TRUE.
2 There are no primary event handlers for the rightMouseUp and rightMouseDown events.

MouseUpOutside Events and the ButtonStyle

Director 6 generates a new event, mouseUpOutside, if the user depresses the
mouse button over a mouse-opaque sprite and then subsequently releases the
mouse button over a different sprite or no sprite. It is not generated if the user
clicks first on the Stage or a non-clickable sprite.

There is no rightMouseUpOutside event. MouseUpOutside is generated whether the
original mouse click was a mouseDown or rightMouseDown event. MouseUpOut-
side events are sent, if appropriate, before and in addition to (not instead of)
mouseUp or rightMouseUp events. The system property the buttonStyle determines
whether Director sends a mouseUp (or rightMouseUp) event following a mouseUp-
Outside event.

              The mouseUpOutside event is sent only to the original sprite over
              which the mouseDown or rightMouseDown occurred. The second
              sprite, over which the cursor is released, receives the mouseUp or
              rightMouseUp event instead (only if the buttonStyle is FALSE, the
              default).

260 Chapter 9  Mouse Events
                                                                                                    Mouse EventsMouse Events

If the buttonStyle is FALSE (the default) a button will highlight as the mouse rolls
over it, even if the mouse button was pressed over another sprite initially. (A
bitmap sprite will only highlight if its Hilight When Clicked option is set in its Cast
Member Properties dialog box. This option is unrelated to the hilite of member
property. Mouse-opaque shape sprites always highlight when clicked.) When the
mouse button is released, the sprite under the mouse will receive a mouseUp (or
rightMouseUp) event. This is called list style in the Lingo Dictionary and is appro-
priate for buttons that make up a list of choices.
If the buttonStyle is TRUE (so called dialog style) only the initial button receiving
the mouseDown will highlight. When the mouse button is released, the sprite
under the mouse will not receive a mouseUp (or rightMouseUp) event, unless it
was the original sprite. In this case, the mouseUp (or rightMouseUp) event is sent
directly to the frame script (and possibly the movie script), bypassing any sprite
scripts or cast scripts attached to the sprite over which the mouse was released.

Double-Clicks

The Boolean system property the doubleClick indicates whether the two last
mouse clicks occurred within the time interval set in the Macintosh or Windows
Mouse Control Panel. The doubleClick depends on the interval between the two
mouseDown or rightMouseDown events, not the two mouseUp or rightMouseUp
events. The Mac Finder is slightly different in that it requires that both the two
mouseDown and two mouseUp events all occur in the prescribed interval. Under
Windows, even if the two clicks involve the two different mouse buttons (right
and left), they would still constitute a double-click. The doubleClick is automati-
cally reset to FALSE when the elapsed interval between clicks exceeds the
operating system's double-click setting.
There is no way to read or change the user-defined double-click interval from
Lingo, but you can create your own double-click handler to simulate this. Like-
wise, you must manually detect triple-clicks, if so desired.

            Consumer titles should avoid requiring the user to double-click the
            mouse. Especially in children's games, you should ignore rapid-fire
            events.

For example, if a single button is used to start and stop a song in a children's
game, many children will click the button rapidly twice. This would start and then
immediately stop the song. If the double-click interval is very short, checking the
doubleClick property will not prevent spurious mouse clicks.

            The doubleClick is a system property that can be checked, not an
            event that can be trapped. The first mouse event is always sent sepa-
            rately from the second mouse event that sets the doubleClick.

                                                                                   Mouse Events 261
Mouse Events

        In Example 9-3, the mouseUp handler will be called twice if the user double-
        clicks--once with the doubleClick equal to FALSE and again with it equal to TRUE.
        Thus, the singleClickAction will be called first, before the user has double-clicked.

        Example 9-3: Responding to Both Single- and Double-Clicks

         on mouseUp
             if the doubleClick then
                 doubleClickAction
             else
                 singleClickAction
             end if

         end

        Solve the problem using the following handler described in detail in Macro-
        media's Lingo Dictionary or online Help under the doubleClick keyword entry.
        (Note that this example tramples any existing timers that use the timer property.
        See Chapter 11, Timers and Dates, for ways to avoid this.)

        Example 9-4: Preventing a Double-Click from Executing the Single-Click Action

         on mouseUp
             if the doubleClick then
                 exit
             else
                 startTimer
                 repeat while the timer < 20
                    -- Simulate check for double-click before
                    -- deciding whether to perform singleClickAction
                    if the mouseDown then
                        doubleClickAction
                        exit
                    end if
                 end repeat
                 singleClickAction
             end if

         end

       Eating Rapid-Fire Clicks

        The system property the lastClick is reset to 0 at the time of each click. Therefore,
        it reflects the time since the current click. It is not useful for preventing double-
        clicks unless you store the previous value in a variable and do some extra math, as
        follows. Example 9-5 prevents clicks closer than 60 ticks (1 second) apart from
        being allowed.

        Example 9-5: Preventing Rapid-Fire Clicks

         property pLastMouseClick

         on mouseDown me
             if voidP(pLastMouseClick) then
                 set pLastMouseClick = the ticks - 61
             end if

        262 Chapter 9  Mouse Events
                                                                                                    Mouse EventsMouse Events

Example 9-5: Preventing Rapid-Fire Clicks (continued)

   if (the ticks - pLastMouseClick) < 60 then
       exit

   else
       set pLastMouseClick = the ticks

   end if
   -- Perform work here.
end

Use this to disable double-clicks entirely:

      set the mouseUpScript = "if the doubleClick then stopEvent"

Multi-button Mice

Most projects use only the left mouse button under Windows and the single
Macintosh mouse button, but Director supports two of the three Windows mouse
buttons and can emulate a two-button mouse on the Macintosh.

            In the authoring mode, Director uses the right mouse button under
            Windows and Control-click on the Macintosh for context-sensi-
            tive menus. Refer to Chapter 2, Being More Productive, in Director in
            a Nutshell for details on these shortcuts.

Note that the following commands ignore the right mouse button:

      on mouseUp
      on mouseDown
      the mouseUpScript
      the mouseDownScript
Conversely, the following do respond to, affect, or reflect the state of the right
mouse button:

      on mouseUpOutside
      on rightMouseUp
      on rightMouseDown
      the clickOn
      the doubleClick
      the emulateMultiButtonMouse
      the lastClick
      the lastEvent
      the mouseDown
      the mouseUp
      the rightMouseDown
      the rightMouseUp
      the stillDown

The following are not affected by the left mouse button:

      on rightMouseUp
      on rightMouseDown

                                                                                   Mouse Events 263
Mouse Events

      the rightMouseDown
      the rightMouseUp

Windows Right Mouse Button

Director for Windows supports the left and right mouse buttons. The middle
button, if any, is always ignored. The Windows 95 Mouse Control Panel allows the
user to configure the mouse for a right-handed user (left mouse button is the
primary button) or a left-handed user (right mouse button is the primary button).
For simplicity, Director uses the primary mouse button in the default case and
refers to the secondary button as the "right" button. For a left-handed mouse
setup, Director treats the physically rightmost button as the primary button, and
events such as rightMouseUp and rightMouseDown would correspond to the user's
physical left mouse button. In short, Director for Windows remaps the buttons
properly, so you don't have to worry about the user configuration. For simplicity, I
refer to the secondary mouse button as the "right" mouse button. Penworks (http://
www.penworks.com) publishes a free utility, SwapEm, which dynamically reverses
the right and left mouse buttons via Lingo.

Table 9-3 shows the events generated by each of the Windows mouse buttons and
the simulated Macintosh mouse buttons. It also shows the properties that each
action sets. Note that mouseUpOutside events may be generated for either mouse
button. See "Mouse Event Idiosynchrasies" for possible errors when using multi-
button mice.

Table 9-3: Mouse Button Events

User Action                  Message Sent    Also Sets Properties
left mouse button click      mouseDown
                                             the mouseDown
left mouse button release    mouseUp         the stillDown
left mouse released outside  mouseUpOutside  the clickOn
right mouse button click     rightMouseDown  the clickLoc
                                             the lastEvent
                                             the lastClick
                                             the doubleClick (if applicable)

                                             the mouseUp

                                             the mouseUp

                                             the rightMouseDown
                                             the mouseDown
                                             the stillDown
                                             the clickOn
                                             the clickLocthe lastEvent
                                             the lastClick
                                             the doubleClick (if applicable)

264 Chapter 9  Mouse Events
                                                                                                                  Mouse Events

Table 9-3: Mouse Button Events (continued)

User Action                   Message Sent    Also Sets Properties

right mouse button release    rightMouseUp    the rightMouseUp
                                              the mouseUp

right mouse released outside  mouseUpOutside  the mouseUp
middle mouse button click     <none>1         N/A
middle mouse button release   <none>1         N/A

1 Some of the third-party Xtras cited at the end of this chapter can read the middle mouse button under Windows.

Note that your standard mouseUp and mouseDown handlers will never be trig-
gered if the user clicks the right mouse button. You can remind him to click the
left mouse button by placing a handler such as this in a movie script:

      on rightMouseDown
          alert "Please use the left mouse button instead."

      end

In practice, using the alert command can interfere with custom palettes. Refer to
Chapter 13, Graphics, Color, and Palettes, and to Chapter 14 in Director in a
Nutshell.

The system property emulateMultiButtonMouse and the state of the Control key
are always ignored in regard to mouse events under Windows.

Macintosh Right Mouse Button

Macintosh mice typically have only one button. If the system property emulate-
MultiButtonMouse is TRUE (the default is FALSE), Director generates rightMouseUp
and rightMouseDown events when you Control-click, as shown in Table 9-4.
Note that the event type (right versus left) is determined when the mouse button is
first pressed, regardless of whether the state of the Control key changes before
the mouse button is released. That is, there is never a rightMouseUp event without
a preceding rightMouseDown event, nor a mouseUp event without a preceding
mouseDown event. Note that mouseUpOutside events may be generated in either
case.

Table 9-4: Macintosh Mouse Button Mapping

User Action                   emulateMulti-ButtonMouse  Control Key Message Sent
mouse click                   FALSE
mouse release                 FALSE                     N/A         mouseDown
mouse click                   TRUE
mouse release                 TRUE                      N/A         mouseUp

                                                        Up          mouseDown

                                                        Up          mouseUp                                       Mouse Events

                                                                Mouse Events 265
Mouse Properties

Table 9-4: Macintosh Mouse Button Mapping (continued)

User Action                            emulateMulti-ButtonMouse     Control Key Message Sent
mouse click                            TRUE
mouse release                          TRUE                         Down     rightMouseDown
mouse release outside original sprite  N/A
                                                                    Down     rightMouseUp

                                                                    N/A      mouseUpOutside

Mouse Properties

Numerous system properties provide information about the current mouse button
state, the last mouse click event, and the current mouse position. Most of these
events can be tested but not set. Table 9-5 summarizes all the system properties
related to the mouse button state, and Table 9-6 summarizes the system proper-
ties related to the position of the mouse cursor.

Table 9-5: Mouse Button State System Properties

Property Name         Usage                                               Left Button Right Button

the buttonStyle       Determines whether mouseUp and rightMou-              

                      seUp event are sent to other sprites or only to

                      the frame following a mouseUpOutside event.

the clickLoc          Point on stage where mouse was last clicked.          

                      See Chapter 5, Coordinates, Alignment, and

                      Registration Points, in Director in a Nutshell.

the clickOn           Sprite number of last mouse-opaque sprite             

                      clicked, or 0 (zero) to indicate the Stage.1

the currentSpriteNum  Sprite number of the sprite to which the current      

                      Lingo handler is attached.1

the doubleClick       Boolean indicating whether last mouse event           

                      constituted a double-click.

the emulateMultiButtonMouse Boolean indicating whether to treat Control-     

                      clicks as right mouse clicks on Macintosh.

the lastClick         Time (in ticks) since last mouse click. See           

                      Chapter 11.

the lastEvent         Time (in ticks) since last mouse click, mouse         

                      roll, or key press. See Chapter 11.

the mouseDown         Boolean indicating whether either mouse button        

                      (left or right) is depressed.

the mouseDownScript   Primary event handler for mouseDown events.         

                      Not called for rightMouseDown events.2

266 Chapter 9  Mouse Events
                                                                                Mouse Properties

Table 9-5: Mouse Button State System Properties (continued)

Property Name            Usage                                               Left Button Right Button

the mouseUp              Boolean indicating whether both mouse buttons         

                         (left or right) are up.

the mouseUpScript        Primary event handler for mouseUp events. Not       

                         called for rightMouseUp events.2

the rightMouseDown       Boolean indicating whether the right mouse             

                         button is depressed.

the rightMouseUp         Boolean indicating whether the right mouse             

                         button is up.

the spriteNum of me      Sprite number of the sprite receiving the              

                         message.1

the stillDown            Boolean indicating whether the mouse button is        

                         still depressed following a mouseDown or right-

                         MouseDown event. Returns FALSE if mouse has

                         been released in the interim.

1 See "Which Sprite Was Clicked On or Rolled Over?" earlier in the chapter.
2 Note there are no rightMouseUpScript or rightMouseDownScript properties.

The properties in Table 9-6 change when the cursor moves, regardless of the state
of the mouse button(s).

Table 9-6: Mouse Location/Movement System Properties

Property Name            Usage
cursor whichCursor       Changes cursor when cursor is over the Stage. See Chapter 14 in Director in
                         a Nutshell.
the cursor of sprite     Changes cursor when cursor is over a particular sprite. See Chapter 14 in
                         Director in a Nutshell.
whichSprite              Time (in ticks) since last mouse click, mouse roll, or key press.
                         Time (in ticks) since last mouse movement.
the lastEvent            Obsolete; required in Director 3.1.3 to detect mouseDown events.
the lastRoll
the immediate of sprite  Obsolete; use the mouseMember instead.
                         Cast member over which cursor is located (even sprite's without scripts).
whichSprite              Character position under cursor in field sprite.
                         Cursor's horizontal position relative to left edge of the Stage.
the mouseCast1
the mouseMember1
the mouseChar2
the mouseH

                                                                             Mouse Properties 267      Mouse Events
Mouse Tasks

Table 9-6: Mouse Location/Movement System Properties (continued)

Property Name                        Usage
the mouseItem2                       Item number under cursor in field sprite. See the itemDelimiter.

the mouseLine2                       Line number under cursor in field sprite.

the mouseV                           Cursor's vertical position relative to top of Stage.
the mouseWord2                       Word number under cursor in field sprite.

the preLoadEventAbort                Determines whether a mouse event aborts preloading.

rollover (n)                         Boolean function, returning TRUE if cursor is over sprite number n., even if
                                     it is invisible, has no scripts, or is obscured by other sprites.1

the rollover                         Indicates the top-most mouse-opaque sprite under the cursor.1
rollover()

the timeoutMouse                     Determines whether mouse clicks reset the timeoutLapsed property to 0.
                                     See Chapter 11.

1 See "Which Sprite Was Clicked On or Rolled Over?" earlier in the chapter.
2 Refer to Chapter 12, Text and Fields, in Director in a Nutshell for details on using the mouseChar, mouseItem, mouseLine, and
mouseWord properties.

Mouse Tasks

Table 9-7 shows the handler(s) and scripts(s) used to accomplish common tasks
related to the mouse. The trick is to place the correct type of handler in the correct
type of script, so that it will be called when the event of interest occurs. For the
purposes of this table, I've made up the following short-hand notations:

 "Mouse click handlers" include on mouseDown, on mouseUp, on right-
      MouseUp, on rightMouseDown, and on mouseUpOutside.

 "Mouse rollover handlers" include on mouseEnter, on mouseLeave, and on
      mouseWithin (new in D6). In D5 use the rollover() function or the rollover
      property instead).

 "Frame handlers" include on exitFrame, on enterFrame, on idle, and on pre-
      pareFrame.

Note that the effect of these handlers depends on the script in which they are
placed.

Table 9-7: Common Mouse Tasks

To Detect This Event or System                                                        In This Type of
Property:                            Use This Type of Handler, Property or Function: Script:

Mouse clicks on all sprites using a  Mouse click handler                                   Cast member script
particular cast member

268 Chapter 9  Mouse Events
                                                                                                    Mouse Tasks

Table 9-7: Common Mouse Tasks (continued)

To Detect This Event or System                                                       In This Type of
Property:                           Use This Type of Handler, Property or Function: Script:

Mouse clicks on a sprite            Mouse click handler                              Sprite script

Mouse clicks ignored by all sprites in Mouse click handler                           Frame script
a frame

Mouse clicks throughout the entire  Mouse click handler                              Movie script
movie otherwise ignored by other
scripts

All left mouse clicks before they are the mouseDownScript or the mouseUpScript       Movie script
passed to individual sprites

Rollovers on all sprites using a partic- Mouse rollover handler                      Cast member script
ular cast member

Rollovers for an individual sprite Mouse rollover handler                            Sprite script

Rollovers for all sprites within a frame rollover(n) or the rollover within a frame  Frame script
                                     handler

Mouse rollovers throughout the entire rollover(n) or the rollover within a frame     Movie script

movie.                              handler

Location of last mouse click        the clickLoc property in a mouse click handler Any script

Current cursor position             the mouseH and the mouseV properties in any Any script
                                    handler

The last sprite clicked             the clickOn property in any handler              Any script

A sprite's channel number           the spriteNum of me or the currentSpriteNum Sprite or Cast
                                    properties in a mouse click handler or mouse roll- member script
                                    over handler

Wait in a frame until the user clicks the mouseDown property in an exitFrame handler Frame script (or

the mouse                           or the Tempo Channel Wait for Mouse Click option Tempo channel)

Creating Draggable Sprites

There are a number of ways to allow the user to drag a sprite around the Stage.
You can set the moveableSprite of sprite property, or you can use the Moveable
checkbox in the Sprite Inspector or Sprite Toolbar.

You can also use the following script to make a sprite moveable. (In Director 5,
you must manually puppet the sprite to move it in this manner. Director 6's auto-
puppeting feature handles this for you.) Note that it accounts for the potential
offset between the click location and the regPoint of the sprite's cast member to
prevent the sprite from jumping when it is first clicked. This is also a good

                                                                                     Mouse Tasks 269     Mouse Events
Mouse Tasks

        example of using point-based math. Refer to Chapter 5 in Director in a Nutshell
        and Chapter 6 of this book.

        Example 9-6: Dragging a Sprite

         on mouseDown me
             set mySprite = the spriteNum of me
             set offset = the loc of sprite mySprite - the clickLoc
             repeat while the stillDown
                 set the loc of sprite mySprite = 
                        point (the mouseH, the mouseV) + offset
                 updateStage
             end repeat

         end mouseDown

      Mouse Traps

        There are a number of ways to prevent mouse events from being processed. See
        "Mouse-Opaque Sprites" at the beginning of this chapter for important details. See
        item 3 below for a way to prevent rollover events from being recognized.

           1. Use the lastClick to prevent rapid-fire mouse clicks from being acknowledged
              (see Example 9-5).

           2. Send the user to a frame in which no sprites have mouse handlers attached,
              so that mouse events are ignored.

           3. Use an unstroked, unfilled QuickDraw rectangle (a shape sprite with a zero-
              width border) in the top-most animation channel with a dummy mouseUp and
              mouseEnter handlers. You can alter its visible of sprite or loc of sprite proper-
              ties to turn it on or off.

           4. You can disable or enable mouse events by calling the handler in
              Example 9-7 with a Boolean flag, such as mouseTrap(TRUE) or mouse-
              Trap(FALSE): Note that this only enables/disables events generated by the left
              mouse button, not the right mouse button.

        Example 9-7: Build a Better Mouse Trap

         on mouseTrap flag
             if (flag = TRUE) then
                 -- Disable mouse events
                 set the mouseDownScript = "stopEvent"
                 set the mouseUpScript = "stopEvent"
             else
                 -- Allow mouse events
                 set the mouseDownScript = EMPTY
                 set the mouseUpScript = EMPTY
             end if

         end mouseTrap

        The Buddy API Xtra (http://www.mods.com.au/budapi) claims to be able to disable
        mouse events under Windows. (I have not personally verified this claim.)

        270 Chapter 9  Mouse Events
                                                                                                     Mouse TasksMouse Events

Simulating Mouse Events

Lingo does not provide a way to send a mouse event to Director's event queue or
to change the cursor's position (the clickLoc, the mouseH, and the mouseV are all
read-only).
The DirectOS Xtra (http://www.directxtras.com/do_doc.htm) claims to be able to
set the cursor position and generate a mouse click for any one of three buttons
under Windows. (I have not personally verified these claims.)
The Buddy API Xtra (http://www.mods.com.au/budapi) claims to be able to set the
cursor position under Windows and also restrict the cursor to certain subsections
of the screen. (I have not personally verified these claims.) A Macintosh version of
the Xtra should be available by the time you read this, but it may not include all
the functionality of the Windows version.
Both the DirectOS and Buddy API Xtras provide many other OS-level functions.
See also Chapter 10, Keyboard Events, and Chapter 14, External Files.
The SetMouse Xtra (http://www.gmatter.com/donationware.html or http://www.
scirius.com) sets the position of the cursor (cross-platform).
You can manually send mouse messages using sendSprite, sendAllSprites, and call,
such as:

      sendSprite (spriteNumber, #mouseDown {, args...})
      sendAllSprites (#mouseUp {, args...})
You can also call a mouse handler in a specific script, using:
      call (#mouseDown, script n {, args...})
You can send a message to a script instance, using:
      call (#mouseDown, scriptInstance {, args...})
If using Director 4.0.4 or Director 5.0, use the form:
      mouseDown (script n {, args...})
as described in the Lingo Issues ReadMe file that came with the 4.0.4 update.

            Mouse messages sent via call are sent only to the specified entity.
            They are not passed to additional scripts through the usual messag-
            ing hierarchy.

Custom Mouse Events
Some Sprite Xtras may generate their own mouse-related events that are more
useful than Director's default events. For example, the Custom Button Xtra's sprites
generate buttonClicked events, but only if the Custom Button is enabled. MouseUp
and mouseDown events are generated even for disabled custom buttons, which is
often undesirable. Likewise, version 3.10 (and later) of the Pop-up menu Xtra

                                                                                    Mouse Tasks 271
Mouse Tasks

        generates a menuItemSelected event when the user selects a valid item from a
        pop-up menu sprite.

      Flushing Mouse Events

        Lingo does not provide a mechanism for flushing pending mouse or keyboard
        events from Director's event queue. We saw earlier how to prevent double-clicks
        or create a "mouse trap" to absorb all mouse events.
        The FlushEvents Xtra (http://fargo.itp.tsoa.nyu.edu/~gsmith/Xtras) is available for
        the Macintosh only (and I haven't tried it personally). The Buddy API Xtra will
        disable mouse events, although it doesn't specifically flush existing events. In most
        cases, there should be no need to flush mouse events. You should instead struc-
        ture your Lingo to allow Director to process mouse events continuously, and
        simply ignore them.

      Mouse Event Idiosyncrasies

        Mouse events are very reliable when you structure your Lingo correctly, but there
        are quirks. Consult this list of idiosyncrasies and work-arounds prior to tearing
        your Lingo apart and your hair out. Also see the quirk list at http://www.update-
        stage.com.

       MIAWs

        Sprites on the main Stage may receive rollover events even when they are
        obscured by a MIAW placed over the Stage. This is especially an issue with roll-
        overs that play sounds. The user will be confused when sounds are triggered for
        no apparent reason. Avoid using MIAWs on top of sprites with rollover Behaviors
        or trying to use a cursor-opaque sprite as the background of the MIAW or in the
        foreground of the main movie (see the earlier section, "Cursor-Opaque Sprites,"
        and the following section, Shockwave).
        MIAWs will continue to trap mouse events over their rect of window area even if
        the MIAW is closed. You must use forget window, or move the window off-screen
        to prevent it from trapping mouse events. See Chapter 6, The Stage and MIAWs, in
        Director in a Nutshell.

       Shockwave

        Unfortunately, Shockwave does not work identically with every version of every
        browser on all platforms. This is often beyond Macromedia's control.
        Allegedly, MIE 4 on the Macintosh doesn't pass mouseUp events to Shockwave
        movies. Search the 1998 DIRECT-L archives (cited in the Preface) for keywords
        such as "MIE" to find one workaround posted by Andrew White.
        Shockwave movies also allegedly respond to rollover events even when the
        browser window is not in the foreground (see the similar problem with MIAWs in
        the previous section).

        272 Chapter 9  Mouse Events
                                                                                                     Mouse TasksMouse Events

Mouse click response in Netscape 4 on the Macintosh may be sluggish through no
fault of Macromedia's. Again, search Macromedia's web site or the DIRECT-L
archives for details and possible work-arounds.
It has also been reported that Shockwave under Windows may not recognize
mouse clicks when the mouse buttons have been configured for left-handed users
in the Mouse control panel.

Editable Text Fields

The mouseUp event is sent to an editable field sprite only if the field does not
have focus. Once it gains focus, an editable field sprite responds to mouseDown
events but not mouseUp events. The mouseUp events are sent straight to the frame
script (bypassing the cast script or the scripts of any obscured sprites). If the edit-
able field sprite loses focus, it will again accept a single mouseUp event.

Right Mouse Button under Window

Under Windows, Director gets confused when multiple buttons are pressed simul-
taneously. The stillDown turns FALSE even if you hold down the original mouse
button while clicking another mouse button.
While the right mouse button is held down, any left mouse button clicks generate
rightMouseDown and rightMouseUp events, rather than the usual left mouse events
(mouseDown, mouseUp and the mouseDownScript and the mouseUpScript).
If the left and right mouse buttons are released simultaneously, subsequent left
mouse clicks continue to generate right mouse events. The error is not corrected
until the actual right mouse button is clicked separately. The same bug occurs in
D5.0.1, D6.0.2, and D6.5 and presumably other versions. One solution is to dupli-
cate mirror all mouseDown and mouseUp handlers with rightMouseDown and
rightMouseUp handlers. An Xtra that disables individual mouse buttons may
provide a complete solution.

Menu Bars

In version 4.0.3 and earlier of Director, mouse clicks in the top 20 pixels of the
screen would be ignored because that area was reserved for the menu bar, even if
no menu was in use. Mouse events could be sent manually using the techniques
described above from a mouseDown handler in a frame script.

Custom Buttons

Custom Buttons did not receive mouseEnter, mouseWithin, and mouseLeave events
in D6.0. Update to Director 6.0.2 or later. Even so, these events become extremely
sluggish if the idleHandlerPeriod is not 0.

Rollovers

Don't use rollover(n) where n is a sprite that is not present in the current Score
frame. Director will use the bounding rect of the last sprite to use that sprite

                                                                                    Mouse Tasks 273
Mouse Tasks
        channel to check for rollovers. Use mouseEnter and mouseLeave events instead, or
        move the sprites in question off stage in a prior frame.
        Mouse events are the core of Director, even more so with new mouse events in
        D6. Revisit this chapter whenever Director is not executing the Lingo you expect it
        to. Improper mouse handling is a common culprit.

        274 Chapter 9  Mouse Events
         Chapter 10Keyboard Events                                                        Keyboard
                                                                                       Events
                          CHAPTER 10

                Keyboard Events

Keyboard Events

Whenever a standard (non-modifier) key is pressed or released, Director gener-
ates a keyDown or keyUp event. Only script attached to editable field sprites, frame
scripts, and movie scripts receive keyboard events. All field sprites, even non-edit-
able ones, can receive the standard sprite events (mouseUp, mouseDown,
mouseEnter, mouseLeave, and so on) Refer to Chapter 7, Strings, for details on
manipulating strings and text. See especially Example 7-7. Refer to Chapter 12,
Text and Fields, in Director in a Nutshell for more details on working with fields.

            Keyboard characters are sent automatically to an editable field sprite
            with keyboard focus, unless the keyDown event is intercepted by an
            onkeyDown handler in a sprite or castmember script first (or explic-
            itly stopped in the keyDownScript primary event handler).

The key being pressed "rides along" with the keyDown event. If an editable field
sprite receives the keyDown event, the last key pressed will be added to the field.
Non-editable fields, editable fields without keyboard focus, and non-field sprites
do not receive keyDown and keyUp events. Rich text sprites can not be edited at
run time. You must use field sprites for dynamic text.
Your keyDown handler will be called even when special characters, such as the
arrow keys, are pressed. Simply pass these onto the field sprite.

            Fields will automatically recognize the arrow keys and Delete key to
            perform rudimentary editing (see "Editing Keys" later in this chapter).

                                                    275
Keyboard Events

        The Tempo channel can be used to wait for a key press (or mouse click) before
        advancing the playback head.

      Author-Time versus Runtime Keyboarding

        Director uses numerous keyboard shortcuts during authoring. Test your keyboard
        event handling from a Projector. For example, the Enter key on the numeric
        keypad is valid at runtime, but during authoring, it stops the movie. The following
        types of keys can be tested accurately only from a projector:
         Numeric Keypad Keys
         F1, F2, F3, and F4 function keys on Macintosh
         Key combinations using Command on the Macintosh, or Control or Alt

              under Windows, such as for menu shortcuts
         Arrow Keys
         Page Up, Page Down, Home, and End Keys
        Note that any open Director windows may interfere with keyboard input. When
        the Paint window has focus, many non-modifier keys switch between various
        paint tools (See Chapter 13, Graphics, Color, and Palettes, covering the Paint
        window in Director in a Nutshell.) To the extent that you do test keyboard events
        from within the authoring environment, close any windows, especially the
        Message window.

                    The Message window accepts keyboard focus and will interfere with
                    the selStart, selEnd, and selection properties.

      Standard Keyboard Events

        Director generates separate keyDown and keyUp messages when a non-modifier
        key is pressed and released. Modifier keys (such as Shift and Control) don't
        generate events by themselves, but rather set system properties such as the shift-
        Down and the controlDown.
        Pressing a non-modifier key also sets the system property the key Pressed, repre-
        senting the current key pressed. Even after a key is released, the system properties
        the key and the keyCode contain information about it. A given script may contain
        handlers that trap both, one, or neither keyboard event (keyUp and keyDown). If a
        sprite traps only the keyDown event, the keyUp event will be passed onto the
        frame script. The keyDown message is sent repeatedly while the key is being held
        down, as long as the playback head is moving.
        Table 10-1 shows how each key event is passed through the Lingo messaging hier-
        archy. A given event may be handled by a primary event handler, sprite script(s),
        cast script, frame script, or movie script. Primary event handlers pass keyboard

        276 Chapter 10  Keyboard Events
                                                                                        Keyboard Events

events by default. Refer also to Example 2-4 and Tables 2-3 and 2-7 in Chapter 2,                                                   Keyboard
Events, Messages, and Scripts.                                                                                                   Events

Table 10-1: Keyboard Event Passing

Event/Message Type  Message Passing
on keyDown1
                    keyDownScriptSprite scripts and/or cast script of editable field sprite with
on keyUp1           keyboard focus2Frame scriptMovie scripts.

                    keyUpScriptSprite scripts and/or cast script of editable field sprite with
                    keyboard focusFrame scriptMovie scripts.

TAB                 Refer to the autoTab of member property.

Quit Keys           Sent to OS, unless the exitLock is TRUE. See Tables 10-4 and 10-5.
Menu Keys3          Used with menu bar, if applicable.

OS Keys             Generally not trappable. See Tables 10-4 and 10-5.

1 A conflict in Director 6 for Windows may prevent Director from receiving keyboard events when RSX is installed.
2 If the keyDown message is not intercepted by a sprite or cast script, the typed character is sent to the field itself. Other-
wise, it is sent only if the keyDown handler includes the pass command.
3 The Command key on the Macintosh, and the Control and Alt keys under Windows may be intercepted by any
installed menus with keyboard shortcuts. See the "Menus" section in Chapter 14, Graphical User Interface Components, in
Director in a Nutshell.

Multiple and Repeat Keys

When you hold down a non-modifier key, Director will repeatedly send out the
corresponding character. It also repeatedly sends the keyDown message. On the
Macintosh, the cpuHogTicks, not the Keyboard control panel, determines the
frequency of auto-repeating keyDown events. Setting the cputlogTicks to 0 gener-
ates repeated keyDown events most often, but it can interfere with other
processes.

If the user presses multiple keys, each one will generate a keyDown message
when it is pressed and a keyUp message when it is released. Therefore, you may
receive multiple separate keyDown events before receiving any keyUp events.

Modifier keys don't generate separate keyDown or keyUp events, but releasing a
modifier key will stop Director from repeatedly sending keyDown events even if
other keys remain pressed. For example, if you hold down the Shift key and the
"A" key, Director will continually send keyDown events. If you then release the
Shift key, Director will stop generating keyDown events even if the "A" key is
still depressed. It will then generate the keyUp event when the "A" key is released.

         Lingo's system properties the key, the keyPressed, and the keyCode
         always indicate the last key pressed. Their values from within a
         keyUp handler may not necessarily reflect the last key released.

                                                                        Keyboard Events 277
Keyboard Properties

Director stores only the most recent keystroke. You can accumulate keystrokes in
a field or accumulate them manually in a variable string or list.
This script will accumulate any keystrokes it traps. Assign it to the keyDownScript
to track all keystrokes.

Example 10-1: Accumulating and Counting Keystrokes

on accumulateKeys
   global gKeyList
   if voidP(gKeyList) then set gKeyList = []
   add (gKeyList, the key)

end accumulateKeys

on startMovie
     set the keyDownScript = "accumulateKeys()"

end startMovie

Instead of accumulating the actual keystrokes, you could simply count them:

      on countKeys
          global gKeyCount
          set gKeyCount = gKeyCount + 1

      end countKeys

      on startMovie
            set the keyDownScript = "countKeys()"

      end startMovie

Keyboard Properties

Table 10-2 summarizes system properties regarding the current keyboard state and
the last key typed. Note that there is no property to indicate whether a non-modi-
fier key is currently being pressed (although you would ordinarily receive repeated
keyDown events during this time). That is, there is no the keyDown property. Refer
to the Xtras cited under "Keyboard Xtras" later in this chapter to detect whether a
non-modifier key is currently being pressed.

Table 10-2: Keyboard System Properties and Constants

Property Name          Usage
BACKSPACE
                       Constant indicating the Backspace key at the upper right of the main
the boxType of member  keyboard (marked "delete" or with an arrow on most keyboards).

charToNum (the key)    Limits the size of keyboard input fields (possible values are #adjust, #limit,
the commandDown        #fixed, and #scroll). See Chapter 12 in Director in a Nutshell.

                       The ASCII value1 of the last key pressed.

                       Boolean indicating whether the Command key (Mac) or the Control key
                       (Windows) is being pressed.

278 Chapter 10  Keyboard Events
                                                                                             Keyboard Properties

Table 10-2: Keyboard System Properties and Constants (continued)

Property Name       Usage                                                                             Keyboard
                                                                                                   Events
the controlDown     Boolean indicating whether the Control key (either platform) is being
                    pressed.

the emulateMultiButton- Boolean indicating whether to treat Control-clicks on the Macintosh as

Mouse               equivalent to right mouse clicks on Windows. See Chapter 9, Mouse Events.

ENTER               Constant indicating the Enter key on the numeric keypad only.

RETURN              Constant indicating the Return key on the main keyboard (usually marked
                    "Enter" on PC keyboards).

the exitLock        Boolean indicating whether to prevent the user from quitting the Projector
the key             with various keyboard shortcuts. Default is FALSE (allows user to quit).2
the keyCode
                    The ASCII character1 of the last key pressed. Does not update in a repeat
                    loop or keyDown handler.

                    The numeric code1 to the last key pressed, not its ASCII value. Unaffected by
                    modifier keys.

the keyDownScript   Sets primary event handler for keyDown events.

the keyPressed      The ASCII character1 of the last key pressed. Updates in a repeat loop. New
                    in D6.

the keyUpScript     Sets primary event handler for keyUp events.

the lastEvent       Time, in ticks, since last key press, mouse click, or any cursor movement.

the lastKey         Time, in ticks, since last key press.

the optionDown      Boolean indicating whether the Option key (Macintosh) or Alt key
                    (Windows) is being pressed.

the preLoadEventAbort Determines whether a key event aborts preloading of cast members (see
                           Chapter 9, Performance and Memory, in Director in a Nutshell).

the shiftDown       Boolean indicating whether either of the two Shift keys is being pressed.
                    Not affected by the state of the Caps Lock key. See the CapsLock Xtra
                    (http://www.gmatter.com/donationware.html).

the timeoutKeyDown  Boolean indicating whether keyboard events reset the timeoutLapsed prop-
                    erty to 0 (default is TRUE). See Chapter 11, Timers and Dates.

1 Refer to Appendix A, ASCII Codes and Key Codes, for a list of key codes and ASCII values.
2 See "Preventing the User from Quitting" later in this chapter.

Determining Which Key Was Pressed

The best method for deciphering keystrokes depends on the type of key for which
you are looking.

                                                                    Keyboard Properties 279
Keyboard Properties

                    Use the key property to distinguish printable characters, such as
                    alphanumerics. Use the keyCode to distinguish non-printable keys
                    such as the arrow keys. Use charToNum(the key) to determine a
                    key's ASCII value.

        The key
              The key returns the character string of the last key pressed, or even a non-
              printable character, such as Ctrl-M. Multiple keys may set the same value for
              the key. For example, the character "7" may be generated from the "7" key on
              either the standard keyboard or the numeric keypad.

        The keyPressed
              The keyPressed returns the same character as the key, but its value updates
              during a repeat loop. The keyPressed is not a Boolean value indicating
              whether a key is pressed.

        ASCII--charToNum(character)
              To determine the ASCII value of a character, use:

                Set asciiVal=chartoNum(the key)
              This is especially useful for distinguishing between uppercase and lowercase
              letters. Refer to Appendix C, Case-Sensitivity, Sort Order, Diacritical Marks,
              and Space-Sensitivity. It is also convenient when working with comparing the
              ASCII values of numeric digits (see Appendix A).
        numToChar(integer)
              NumToChar() converts a number from 0 to 255 into the corresponding char-
              acter from the ASCII table. Use it to add non-printable characters to an output
              string, such as:

                set linefeed = numtochar (10)
              Note that ASCII values above 127 vary for different fonts. Refer to the char-
              acter mapping feature of the FONTMAP.TXT file as covered in Chapter 12, in
              Director in a Nutshell. Use the Macintosh Key Caps desk accessory or the
              Windows Character Map utility (under the Windows 95 Start Menu under
              ProgramsAccessories) to view various characters in different fonts. Under
              Windows. you can create ASCII characters by holding down the Alt key
              while typing in their ASCII code on the numeric keypad with Num Lock on
              (that is, Alt+6+5 will create a capital "A").
        The keyCode
              The keyCode returns a fixed number based on the key's position on the
              keyboard. It is unaffected by modifier keys and is unique for each key.
              Whereas the key properties returned by the "7" from the standard keyboard
              and from the numeric keypad are identical, their keyCode properties are
              different. Use the keyCode to detect keys for which there are no Lingo equiva-
              lents, such as the arrow keys, or whose ASCII values are not standardized. All
              keyboards on all platforms seem to send the same key codes for each key.

        280 Chapter 10  Keyboard Events
                                                                               Keyboard Properties   Keyboard
                                                                                                  Events
Refer to Appendix A for a complete list of key codes and ASCII
codes.

Detecting the Key's Case

The key differentiates between uppercase and lowercase characters, such as "q"
and "Q," but Lingo ignores strings' case when compared using the equals sign (=)
or the not equals sign (<>). The following is therefore somewhat redundant:

      if the controlDown and (the key = "Q" or the key = "q") then
          statement(s)

      end if

There is no point in checking the state of the Shift key to distinguish between
uppercase and lowercase characters, or other keys that have different shifted
states. To distinguish between uppercase and lowercase letters, check their ASCII
values using charToNum(). See Appendix C for complete details, especially
Examples C-3 and C-5, which perform case-sensitive comparision and convert text
to uppercase. See "Shift Key" later in this chapter.

Modifier Keys

Modifier keys are keys that do not generate their own keyDown events but rather
affect the character generated by other keys. In many cases, they indicate special
commands, such as with custom menus (see the "Menus" section Chapter 14 of
Director in a Nutshell.). The modifier keys are different between Macintosh and
Windows. Table 10-3 shows the system properties and constants that correspond
to various keys.

Table 10-3: Cross-Platform Key Equivalents and Properties

Key          Macintosh                    Windows
Alt Key      N/A                          the optionDown
Command Key  the commandDown              N/A
Control Key  the controlDown              the controlDown, or
                                          the commandDown
Option Key   the optionDown               N/A
Shift Key    the shiftDown                the shiftDown
Caps Lock    Can't tell without Xtra      Can't tell without Xtra
BACKSPACE    delete                       backspace
ENTER1       Enter key on numeric keypad  Enter key on numeric keypad

                                          Keyboard Properties 281
Keyboard Properties

Table 10-3: Cross-Platform Key Equivalents and Properties (continued)

Key                  Macintosh                     Windows
RETURN1                                            Enter key on main PC keyboard
                     Return key on main Macintosh
                     keyboard

1 ENTER refers only to the Enter key on the numeric keypad. The key labeled "Enter" on the main portion of PC keyboards
generates a RETURN character. The Enter key on the numeric keypad will stop the movie during authoring, so you can trap it
only from a Projector.

         The modifier key properties update if the state of the relevant key
         changes, even during a handler's execution. To ensure that you are
         checking the initial state of a modifier key, store the appropriate
         Lingo property in a variable.

You can then check the variable throughout the handler without fear of its
changing. Note below that we store the value of the shiftDown, but not the value
of the key. The latter does not change during a Lingo handler.

Example 10-2: toring the State of Modifier Keys

on keyDown
   set shiftKeyDown = the shiftDown
   if shiftKeyDown and the key = "A" then
       statement
   else if shiftKeyDown and the key = "B" then
       statement
   end if

end

In reality, example 10-2 is too short to necessitate storing the shiftDown. But
suppose you want to detect whether the Control key was pressed when the
Projector was first started, and if so, skip the introduction of your presentation.
You should store the controlDown into a global variable (in your prepareMovie
handler) that you can use long after the Control key is released.

Shift Key
      Whereas the Shift key capitalizes alphabetic keys, Lingo string comparisons
      using "=" and "<>" are case-insensitive. (See Appendix C for details.) You may
      want to treat the shifted and unshifted versions of some non-alphabetic keys
      as the same thing. For example, if the "+" key increases the volume, you may
      want to check for the unshifted version of the same key ("=" on most
      keyboards) also. You can also use the keyCode to identify a physical key
      regardless of the Shift key's state.

Caps Lock

      Lingo does not recognize the Caps Lock key separately, although using it
      will capitalize alphabetical characters. See the CapsLock Xtra (http://www.
      gmatter.com/donationware.html) to detect its state.

282 Chapter 10  Keyboard Events
                                                                                           Keyboard Properties   Keyboard
                                                                                                              Events
Alt Key (Windows)
      The optionDown reflects the state of the Alt key, but Alt key combinations
      are generally trapped by Windows before reaching Director. (There is no the
      altDown property.) By definition, if you are trying to simulate keys that are
      trapped by Windows, they will be trapped by Windows! Alt key combina-
      tions such as Alt-] are sent to Director, but Alt-A through Alt-Z are not. The
      Alt key will also access custom menus defined with the installMenu
      command. The Xtras cited under "Keyboard Xtras" below can trap or disable
      the Alt key in limited cases.

Option Key (Macintosh)
      The Option key is used for alternate actions, usually in combination with the
      Command key.
      Use the optionDown to provide alternate functionality for debugging
      purposes., as in Examples 3-7, 3-8, and 3-9.

Command Key (Macintosh)
      The Command key accesses menu shortcuts on the Macintosh. Certain key
      combinations are trapped by Director itself during authoring or by the OS
      during Projector playback and won't reach your handler. Refer to the exitLock
      and the commandDown.

Control Key
      The Control key, along with the emulateMultiButtonMouse property, is used
      to simulate a multibutton mouse on the Macintosh. Certain key combinations
      are trapped by Director itself during authoring, or by the OS during Projector
      playback, and won't reach your handler. Refer to the exitLock.

            Use the commandDown. instead of the controlDown property when
            you want the Control key to perform an operation under Windows
            and the Command key to perform the analogous operation on the
            Macintosh (as is the convention).

Special Key Combinations

Many keyboard combinations are intercepted by the OS instead of being sent to
your keyDown and keyUp handlers. These key combinations perform some special
OS operation, such as a screen grab, quitting the Projector, or switching to another
program. The exitLock property disables most of the quit keys, but some key
combinations can not be prevented without an Xtra.

            Browsers may also intercept certain key combinations, preventing
            them from reaching your Shockwave movie.

                                                                          Keyboard Properties 283
Keyboard Properties

Table 10-4 shows Windows-specific key combinations. To trap the function keys
on either platform, use the keyCode as described later in this chapter.

Table 10-4: Special Windows Key Combinations

Key Combination      Default Action                        How to Prevent It

Escape               Quits Projector.                      the exitLock = TRUE
Alt-F4               Quits Projector.                      the exitLock = TRUE
Ctrl-Q               Quits Projector.                      the exitLock = TRUE
Ctrl-. (period)1     Quits Projector.                      the exitLock = TRUE

Ctrl-W               Does not quit Projector, despite claims N/A

                     in documentation.

Alt Key              Combinations including Alt and an     Not preventable
                     alphabetic key ("A" through "Z") are
Alt-Tab              intercepted by the Windows and not    Buddy API Xtra or DirectOS Xtra2
Ctrl-Alt-Del         passed to Director.                   Buddy API Xtra or DirectOS Xtra2

                     Switches between running Windows
                     tasks.

                     Brings up task list, with option of
                     restarting computer.

Ctrl Key             Executes menu shortcut.               Define shortcuts with installMenu
                                                           command

Ctrl-Print Screen    Screen grab.                          Not preventable without Xtra
Windows95 Key        Windows 95 Start Menu.                DirectOS Xtra2

1 The Ctrl-. (period) combination works with the period on both the main keyboard and the numeric keypad.
2 See "Keyboard Xtras" later in this chapter. Some functions may not work under Windows NT.

Table 10-5 shows Macintosh-specific key combinations.
Table 10-5: Special Macintosh Key Combinations

Key Combination      Default Action                               How to Prevent It
Escape
Command-Q            No effect.                                   N/A
Command-. (period)1
Command-W            Quits Projector.                             the exitLock = TRUE

                     Quits Projector.                             the exitLock = TRUE

                     Does not quit Projector, despite claims N/A
                     in documentation.

284 Chapter 10  Keyboard Events
                                                                 Keyboard Properties

Table 10-5: Special Macintosh Key Combinations (continued)

Key Combination         Default Action                           How to Prevent It                                             Keyboard
                                                                 Requires third-party Xtra                                  Events
Command-Option-Esc      Gives user option of Force Quitting
                        Projector.                               Requires third-party Xtra

Restart Key, or Restart Button, Gives user option of restarting  Define shortcuts with installMenu
                                                                 command
or Ctrl-Option-Restart  computer.                                OSutil Xtra2

Command Key             Executes menu shortcut.

Command-Shift-3         Screen grab.

1 The Command-, (period). combination works with the period on both the main keyboard and the numeric keypad.
2 OSutil's OSSetScreenDump method can disable basic Macintosh screen captures. See "Keyboard Xtras" later in this chapter.

Controlling the Quit Sequence

You may wish to perform some cleanup or post a confirmation or goodbye
message when the user quits the projector. To trap special keyboard combina-
tions before they abort the Projector, you'll need to set the exitLock to TRUE.

Provide an exit button or key combination that quits the Projector or
the user will be stuck! Disabling the quit keyboard combinations is
impolite for boring presentations.

Example 10-3: Preventing the User from Aborting

on prepareMovie --use an on startMovie handler in D5
   set the exitLock = TRUE

end

Trapping Quit Keys Manually

If you've set the exitLock to TRUE, you can then trap the quit keys manually in a
movie script. Example 10-4 traps the Escape key, Command-Q, or Command-.
(period) on the Macintosh and Alt-F4, Control-Q, or Control-. (period)
under Windows. ConfirmQuit is a custom routine left as an exercise to the reader.
See Chapter 15, The MUI Dialog Xtra, or Chapter 14, Graphical User Interface
Components, in Director in a Nutshell for details on creating custom dialog boxes
to present the user with multiple choices.

Example 10-4: Trapping the Quit Keys

on keyDown
   -- Trap the Escape key by checking for ASCII 27
   -- Also trap Alt-F4 under Windows.
   if charToNum(the key) = 27 or 
       (the platform starts "Windows" and the optionDown 

                                                                          Keyboard Properties 285
Keyboard Properties

        Example 10-4: Trapping the Quit Keys (continued)

                  and the keyCode = 118) then
                 stopEvent
                 if confirmQuit() then

                  quit
                 end if
                 exit
             end if

             if the commandDown then
                 -- Prevent Cmd/Ctrl-Q andCmd/ Ctrl-. from aborting
                 if (the key = "Q" or the key = ".") then
                    stopEvent
                    if confirmQuit() then
                        quit
                    end if
                 else
                    pass
                 end if

             else
                 pass

             end if
         end keyDown

      Keyboard Focus

        Only editable field sprites are eligible to receive keyboard focus. An editable field
        receives focus if the user clicks on the field or "tabs" to it. A field will also receive
        focus if it is the only editable field in the current Score frame. Rich text fields are
        never editable at runtime. Refer to Chapter 12 in Director in a Nutshell for details.

                    You can pass keyboard focus to a particular field sprite by setting its
                    editable of sprite property to TRUE (even if it is TRUE already).
                    Remove keyboard focus by setting both its editable of sprite and edit-
                    able of member properties to FALSE. Test your Lingo scripts with the
                    Message window closed (it may steal the focus if it is open).

        If multiple field sprites are editable, there is no easy way to determine which field
        currently has focus. You can record a field sprite's number in a global variable
        whenever it receives a keyDown or mouseDown event, but no events are sent
        explicitly when a field sprite gains or loses focus nor is there a system property
        that indicates the field with keyboard focus.

       Creating Editable Fields

        The editable of member and editable of sprite properties determine whether the
        user can edit the field cast member associated with a field sprite at runtime. Prior
        to D5 field cast members were callled #text cast members.) The member property
        corresponds to the Editable checkbox in the Field Cast Member Properties dialog.

        286 Chapter 10  Keyboard Events
                                                                                           Keyboard Properties   Keyboard
                                                                                                              Events
The sprite property corresponds to the Editable checkbox in the Sprite Toolbar or
Sprite Inspector. (In Director 5, the Editable checkbox is to the left of the sprite
channels in the Score window.)

            A field is user-editable if either its editable of sprite or editable of
            member property is TRUE. Non-field sprites are never editable, even
            if their editable of sprite property is TRUE.

Auto-Tabbing
Director allows you to tab between editable fields by setting the autoTab of
member property to TRUE or setting the Tab to Next Field checkbox in the Field
Cast member Info Dialog box.
AutoTab determines whether the Tab key is intercepted by an editable field or
whether it passes focus to the next editable field sprite. The sprites' channel
numbers, not their on-stage positions, determine the tabbing order. AutoTab does
not determine whether a field sprite can receive focus. That is determined by
whether the field is editable.
You must manually trap the Return key and arrow keys to use them to navigate
between editable fields. See Example 10-10.

Highlighted Text and the Insertion Point
Use the hilite command or the selStart and the selEnd properties to highlight a
portion of a field, and the selection, the selStart, and the selEnd properties to deter-
mine the currently highlighted characters. The Message window interferes with the
selStart, selEnd, and selection properties. Activate your test scripts by attaching
them to buttons rather than testing them from the Message window.

            You must set the selEnd before setting the selStart to get them to
            update reliably.

The selStart and the selEnd represent positions after characters. If the selStart and
the selEnd are both 1, the insertion point is between characters 1 and 2. Set them
both to 0 to insert keystrokes before the first character.

Example 10-5: Setting the Insertion Point
on setInsertionPoint fieldSprite, cursorPosition

   -- Force focus onto this sprite
   set the editable of sprite fieldSprite = TRUE
   -- Set the selEnd first for reliability
   set the selEnd = cursorPosition
   set the selStart = cursorPosition

                                                                          Keyboard Properties 287
Filtering Keyboard Input

        Example 10-5: Setting the Insertion Point (continued)

             return cursorPosition
         end setInsertionPoint

        This forces focus onto a sprite and positions the cursor at the end of its field:

                on beginSprite me
                    set mySprite = the spriteNum of me
                    setInsertionPoint (mySprite, 
                             length(field (the member of sprite mySprite)))

                end beginSprite
        Setting the selEnd and the selStart to different values highlights the text between
        them (or you can use the hilite command).

        Example 10-6: Setting the Highlight in a Field

         on hilightText fieldSprite, startChar, endChar
             set the editable of sprite fieldSprite = TRUE
             -- Set the selEnd first for reliability
             set the selEnd = endChar
             set the selStart = startChar-1
             return the selection

         end hilightText

        This highlights characters 1 to 3 of the current sprite (assumed to be a field):

                hilightText (the currentSpriteNum, 1, 3)

     Filtering Keyboard Input

        In the default case, any characters typed by the user will appear in an editable
        field. You can intercept keyboard input, before it appears in the field, with a
        keyDown handler attached to the field sprite. Movie-wide key events can also be
        trapped with the keyDownScript. Refer to the previous examples.

Keyboard events not trapped by a field's sprite or cast script are
passed to the frame script or movie scripts. If you attach a keyDown
handler to a sprite, you must include the pass command for the field
cast member to actually receive the keyboard character(s).

It is possible to attach multiple keyDown handlers to a single sprite. Table 10-6
shows what happens when keyDown events are passed or consumed explicitly or
implicitly. See Table 10-1 for the event passing order.

Table 10-6: KeyDown Event Passing

Command Used in First  Passed to Other  Passed to Editable Field?
Behavior               Behaviors?       Only if all Behaviors issue pass

pass                   Yes

288 Chapter 10  Keyboard Events
                                               Filtering Keyboard Input

Table 10-6: KeyDown Event Passing (continued)

Command Used in First      Passed to Other  Passed to Editable Field?                             Keyboard
Behavior                   Behaviors?                                                          Events
                           Yes              No, but later Behaviors can manually append char-
<None specified> or dont-                   acter to field
PassEvent                  No
                                            No
stopEvent

Don't forget to trap undesirable keys when requesting user input. Example 10-7
shows how to filter out certain keys and perform some action when the Return or
Enter key is pressed. This keyDown handler attached to a field sprite prevents the
user from entering any spaces.

Example 10-7: Disallowing Characters

on keyDown me
   if the key = RETURN or the key = ENTER then
      -- Process the user entry
       set contents = the text of member 
          (the member of sprite (the spriteNum of me))
       alert "You entered" && contents
   else if the key = SPACE then
       -- Beep if they enter a SPACE
       beep
   else
       -- This sends the key event onto the editable field
       pass
   end if

end keyDown

You generally will not want to allow the user to include the Return
character in a field. Trap the Return key unless allowing multiline
inputs.

The previous example traps the Return character explicitly. Example 10-8 rejects
the Return character because it allows only the digits 0 through 9 to be passed
through. It assumes that there is a separate submit button that reads the field's
contents.

Example 10-8: Allowing Only Specific Characters

on keyDown
   if ("0123456789" contains the key) then
       pass
   else
       stopEvent
   end if

end keyDown

                                               Filtering Keyboard Input 289
Filtering Keyboard Input

        Reader Exercise: Modify Example 10-8 to allow other characters used to enter
        numbers, such as "=," "-", and ".".

        To limit the length of a field, you can set the boxType of member to either #fixed
        or #limit. Refer to Chapter 12 in Director in a Nutshell. That's usually easier than
        trying to track the length of the field manually. If you try to stop user input after a
        certain number of characters, you must allow for the possibility that the user is
        pressing the Delete key or that highlighted characters will be deleted by the next
        key pressed. It is easier to check the final length of the string once the user has
        "submitted" it, rather than testing it at every keystroke.

      Simulating a Password Entry Field

        Because an onkeyDown handler in a score script or castscript intercepts keys
        before they are passed to the field, you can modify them before they are
        displayed. You could capitalize all letters, for example. Example 10-9 simulates a
        password entry field using asterisks. Note that the field is updated manually, and
        that the original key is not passed with pass (unless it is one of the standard
        editing keys). Manually passing characters to a field requires us to manually simu-
        late some of the things that Director does automatically if we just pass the
        characters (we want to send asterisks instead). Note the tricks we use to figure out
        whether to insert the characters or replace highlighted text and how we reset the
        cursor insertion point.

        Example 10-9: Password Entry Field

         property pPassword
         property pMyMember

         on beginSprite me
             set pMyMember = the member of sprite (the spriteNum of me)
             -- Clear the password field
             set pPassword = EMPTY
             put EMPTY into member pMyMember

         end

         on keyDown me
             -- Mask the field with asterisks. Change this to
             -- "set maskCar = the key" to see password entry
             set maskChar = "*"

             if the key = RETURN or the key = ENTER then
               -- Check the password when they hit RETURN or ENTER
              -- Perhaps check name against a master list or file.
                 if verifyPassword (pPassword) = TRUE then
                    go frame "Top Secret"
                 else
                    alert "Access Denied"
                 end if

             else if isEditingKey() then
               -- Allow the editing keys (arrows, delete) to pass
                 pass

             else

        290 Chapter 10  Keyboard Events
                                                                                     Filtering Keyboard Input   Keyboard
                                                                                                             Events
Example 10-9: Password Entry Field (continued)

       -- Determine what portion of the field to replace
       set insertPoint = max(1, the selStart + 1)
       set endPoint = max(1, the selEnd)
       -- We're inserting at the cursor location
       if insertPoint = endPoint then

           -- Add the key to the secret password
          put the key before char insertPoint of pPassword
           -- But display the masking character (asterisks)
          put maskChar before char insertPoint [LC]

                  of member pMyMember
       else

         -- Replace highlighted characters similar to above
          put the key into char insertPoint to endPoint [LC]

                  of pPassword
          put maskChar into char insertPoint to endPoint [LC]

                  of member pMyMember
       end if
       -- Update the cursor insertion point manually
       -- Set the selEnd first for reliability
       set the selEnd = insertPoint
       set the selStart = insertPoint
   end if
end keyDown

-- Check for common editing keys that we'll allow through (See Example 10-10.)
on isEditingKey

   case (the key) of
       BACKSPACE, TAB: return TRUE

   end case

   case (the keyCode) of
       -- This checks for delete key and the arrow keys
       51, 117, 123, 124, 125, 126:
          return TRUE
       otherwise:
          return FALSE

   end case
end isEditingKey

-- Write your own verification routine
on verifyPassword password

 If password = "platypus" then
 else return TRUE
 end if return FALSE
end

Editing Keys

By default, editable fields support only the Delete (Backspace) key and the
arrow keys for editing. The left and right arrow keys move the cursor one char-
acter, and the up and down arrow keys jump to the beginning and end of the
field. The Tab key jumps between fields (assuming the autoTab of member prop-
erty is TRUE.).

                                                                    Filtering Keyboard Input 291
Filtering Keyboard Input

You must manually implement cut, copy, paste. You may want to make the up
and down arrow keys move between fields. Use the Return key to jump to the
next field of a multifield input screen, or submit a single field entry.

Table 10-7 shows the keyCodes of common editing keys you can use to control
keyboard navigation between multiple editable fields.

Table 10-7: Editing Keys

Key                       ASCII  the keyCode
RETURN
Left Arrow                13     36
Right Arrow
Up Arrow                  28     123
Down Arrow
Help (or insert)          29     124
Home
Page Up                   30     126
Page Down
End                       31     125
BACKSPACE
Del (keypad)              5      114
ENTER
                          1      115

                          11     116

                          12     121

                          4      119

                          8      51

                          127    117

                          3      76

You can allow the user to navigate between editable fields (see "Keyboard Focus"
earlier in this chapter) using the up and down arrows, and the Return, Home, and
End keys, as follows. (Use the autoTab of member property or AutoTab checkbox
to jump between fields without Lingo scripting.)

Example 10-10: Special Handling of Editing Keys

on keyDown
 case (the keyCode) of
       125: -- Down arrow
                -- Perhaps send focus onto the next field
                -- by setting its editable of sprite property
                126: -- Up arrow
               -- Perhaps send focus onto the previous field
                115: -- Home key
               -- Send keyboard focus to first field
                119: -- End key
               -- Switch keyboard focus to last field
       otherwise:

292 Chapter 10  Keyboard Events
                                                                                     Filtering Keyboard Input   Keyboard
                                                                                                             Events
Example 10-10: Special Handling of Editing Keys (continued)
            if the key = RETURN then
                 -- Process field or jump to next field
            else
                pass
            end if

   end case
end

Numeric Keypad Input

Director ignores input from the numeric keypad by default. To allow numeric
keypad input, you must evaluate the keyCode generated by each key, and if it
corresponds to a key from the numeric keypad, append the appropriate character
to the field.
Table 10-8 shows the keys you may want to trap for interpreting numeric keypad
input. Note that the keyCode numbers skip a beat between the "7" and the "8" on
the keypad. In Director 5, the "7" and "8" keys on the keypad erroneously
returned the same code

            Whenever dealing with numbers, don't confuse the characters "0"
            through "9," whose ASCII values range from 48 to 57, with the ASCII
            values 0 through 9, which are all unprintable control characters. See
            Appendix A.

Example 10-11 reads numbers from the keypad (note the workaround to handle
the fact that the keyCodes skip number 90).

Example 10-11: Trapping the Numeric Keypad Keys
on keyDown me

  -- This handles the keypad chars 0 through 7
   if (the keyCode >= 82) and (the keyCode <= 89) then

       set thisChar = numToChar (the keyCode-34)
   -- This handles the keypad chars 8 and 9
   else if (the keyCode >= 91) and (the keyCode <= 92) then

       set thisChar = numToChar (the keyCode-35)
   else

       -- Let all other keys pass through
       set thisChar = the key
   end if
   put thisChar after member 

            (the member of sprite (the spriteNum of me))
end

                                                                    Filtering Keyboard Input 293
Filtering Keyboard Input

Table 10-8: Numeric Keypad Codes

Key           ASCII              keyCode  Key  ASCII  keyCode
                                 65
. (period) 46                    76       0    48     82
                                 69
Enter         3                  78       1    49     83
                                 67
+             43                 75       2    50     84
                                 81
-             45                 71       3    51     85

*             42                          4    52     86

/             47                          5    53     87

=             61                          6    54     88

num lock/clear 27                         7    55     89

                                          8    56     91

                                          9    57     92

Function Keys

To trap the function keys, use the key codes shown in Table 10-9. Like other key
codes, these are the same on the Macintosh and Windows.

Table 10-9: Function Keys

Function Key              ASCII  keyCode
F1
F2                        16     122
F3
F4                        16     120
F5
F6                        16     99
F7
F8                        16     118
F9
F10                       16     96
F11
F12                       16     97
F13
                          16     98

                          16     100

                          16     101

                          16     109

                          16     103

                          16     111

                          16     105

294 Chapter 10  Keyboard Events
                                                                                               Keyboard Tasks

Table 10-9: Function Keys (continued)

Function Key          ASCII        keyCode                                                                Keyboard
F14                                                                                                    Events
F15                   16           107

                      16           113

Keyboard Tasks

Table 10-10 shows the handler(s) and scripts(s) used to accomplish common tasks
related to the keyboard. The trick is to place the correct type of handler in the
correct type of script, so that it will be called when the event of interest occurs.

Table 10-10: Common Keyboard Tasks

To Detect                          Use This Type of Handler or         In This Type of Script
                                   Property

Keyboard input for all sprites using a on keyDown                      Castmember script
particular cast member

Keyboard input for a sprite        on keyDown                          Sprite script

Keyboard input ignored by all sprites in on keyDown                    Frame script
a frame

Keyboard input throughout the entire on keyDown                        Movie script
movie otherwise ignored by other
scripts

All keyboard input before it is passed set the keyDownScript           Place primary event handler in
to individual sprites or frames.                                       movie script

Keyboard input from numeric keypad on keyDown                          Sprite or cast member script

Key being pressed at any time      set the keyDownScript               Place primary event handler in
                                                                       movie script

Key being released at any time     set the keyUpScript                 Place primary event handler in
                                                                       movie script

Modifier keys                      Check the commandDown,              Any

                                   controlDown, optionDown, or shift-

                                   Down property

The last key pressed               Check the key, keyPressed, keyCode Any
                                   property

Whether a specific key is pressed  Use third-party Xtras described Any
                                   under "keyboard xtras" later in this
                                   chapter

                                                                            Keyboard Tasks 295
Keyboard Tasks

        See "Keyboard Focus" earlier in the chapter to force keyboard focus on a sprite.
        There is no easy way to detect which sprite has keyboard focus.

      Key Trap

        There are a number of ways to prevent key events from being processed. You can
        simply send the user to a frame in which no sprites have key handlers attached.
        You can disable or enable key events by calling the following handler with a
        Boolean flag, such as keyTrap(TRUE) or keyTrap(FALSE).

        Example 10-12: Key Trap
         on keyTrap flag

             if (flag = TRUE) then
                -- Disable key events
                 set the keyDownScript = "stopEvent"
                 set the keyUpScript = "stopEvent"

             else
                -- Allow key events
                 set the keyDownScript = EMPTY
                 set the keyUpScript = EMPTY

             end if
         end keyTrap

      Simulating Keyboard Events

        Lingo does not provide a mechanism for setting the key, the keyCode, or the
        keyPressed or for directly sending a keyboard event to Director's event queue. (See
        the "keyboard Xtras" later in this chapter.)
        You can manually send keyboard messages using sendSprite, sendAllSprites, and
        call, such as:

                sendSprite (spriteNumber, #keyDown {, args...})
                sendAllSprites (#keyUp {, args...})
        You can also call a keyDown handler in a specific script, using:
                call (#keyDown, script n {, args...})
        You can send a message to a script instance, using:
                call (#keyDown, scriptInstance {, args...})
        If using Director 4.0.4 or Director 5.0, you can use the forms:
                keyDown (script n {, args...})
                send (#keyDown, scriptInstance {, args...})

                    Keyboard messages sent manually are sent only to the specified
                    entity. They are not passed to additional scripts through the usual
                    messaging hierarchy.

        296 Chapter 10  Keyboard Events
                                                                                                 Keyboard Tasks   Keyboard
                                                                                                               Events
Keyboard Xtras

Xtras provide a number of keyboard-related functions not possible via Lingo
alone.

Flushing Keyboard Events

Lingo does not provide a mechanism for flushing pending mouse or keyboard
events from Director's event queue. A number of older (often unsupported)
XObjects, such as "Johnny" and "MISC_X" flushed pending mouse and keyboards
events. The FlushEvents Xtra (http://fargo.itp.tsoa.nyu.edu/~gsmith/Xtras) by Geoff
Smith is available for the Macintosh only (and I haven't tried it personally).
The OSutil Xtra (http://www.ddce.cqu.edu.au/imu/tools/Director/Xtras) by Paul
Farry has an OSFlushEvents method that purportedly flushes mouse and keyboard
events. I've used this Xtra for other chores with good success, but I have no expe-
rience with this method.
The KeyPoll Xtra (see next section) can disable keyboard input but doesn't flush
pending events.

Polling for Keys and Multiple Simultaneous Keys

The KeyPoll Xtra (http://www.gmatter.com/donationware.html) (developed by
Brian Gray, formerly of Macromedia) allows you to do the following on all major
platforms:
 Check whether the key with a specific keyCode is being pressed.
 Get a list of the keyCodes of all keys currently being pressed.
 Disable/enable all keyboard events from reaching the system-level queue.
Allegedly, the Macintosh reports up to two character keys being pressed in addi-
tion to any combination of the five modifier keys or the arrow keys. Brian Gray
reports that more than two characters keys are sometimes detectable. Details can
be found in Inside Macintosh: Macintosh Toolbox Essentials at http://developer.
apple.com/.
The CapsLock Xtra (also at http://www.gmatter.com/donationware.html) can detect
the state of the Caps Lock key.
See also the Buddy API and DirectOS Xtras in the next section.

Sending Key Events and Disabling Keys

The Buddy API Xtra (http://www.mods.com.au/budapi) claims to be able to check
which keys have been pressed (and also simulate key events and disable keyboard
input) under Windows using the baSendKeys, baKeyIsDown, baKeyBeenPressed,
baDisableKeys, and baDisableSwitching methods. (I have not personally verified
these claims, but I have heard uniformly positive comments about Buddy API in
general and their tech support was responsive.) A Macintosh version of Buddy API
should be available by the time you read this.

                                                                                Keyboard Tasks 297
Keyboard Tasks

        The DirectOS Xtra (http://www.directxtras.com/do_doc.htm) claims to be able
        check which keys have been pressed (and also disable certain key combinations)
        under Windows. (I have no personal experience with this Xtra).
        Both the DirectOS and Buddy API Xtra provide many other OS-level functions. See
        also Chapter 9 and Chapter 14, External Files.
        See also the other Xtras listed earlier.

      Keyboard Event Idiosyncrasies

       Authoring Caveats

        During authoring, Director may intercept certain keyboard events. Refer to the
        discussion at the beginning of this chapter. When trying to edit or highlight text in
        editable field sprites, Director's Message window is a frequent trouble-maker.
        Close all Director windows, or test from a Projector if necessary.

       Kiosks Without Keyboards

        If you are creating a kiosk without a keyboard, you can use a simulated graphic
        touch-screen to allow for user input. Simply have each sprite's mouseUp handler
        append the appropriate character to the input field.

       RSX Conflict

        RSX is a sound driver from Intel that has some conflicts with Director for
        Windows. RSX can prevent Director for Windows (D6.0, D6.0.1, and D6.0.2)
        Projectors played full-screen from receiving keyboard events. Macromedia has
        apparently acknowledged the problem, but no fix has been released as of May
        1998. If possible, ask your users to disable RSX.

       Keyboard Events to Frame and Movie Scripts

        There have been reports that frame scripts and movie scripts may not receive
        keyboard events unless at least one editable field sprite is present in the current
        frame. Place one off-stage, if necessary. I have not seen this behavior myself, and
        it is not clear that it is a separate issue from the RSX conflict.

       MIAWs

        A movie-in-a-window whose window has focus will intercept keyboard events
        even if it does not have any editable text fields. You can click on the Stage to
        ensure that it has focus so that the main movie receives keyboard events properly.
        In a movie script of the MIAW, use the code shown in Example 10-13 to send
        keyboards events to the Stage.

        Example 10-13: Passing Key Events from MIAWs
         on keyDown

             tell the stage
                 do (the keyDownScript)

        298 Chapter 10  Keyboard Events
                                                                                                 Keyboard Tasks   Keyboard
                                                                                                               Events
Example 10-13: Passing Key Events from MIAWs (continued)
   end tell

end keyDown

In the main movie, you can define the keyDownScript to execute the handler of
your choice. The main movie can check the key to determine the last key pressed,
or even use moveToFront the stage to bring itself to the foreground.
In the main movie you might use:

      on startMovie
          set the keyDownScript = "customKeyDownHandler"

      end

      on customKeyDownHandler
          put "The key is" && the key
          -- Do any custom keyboard handling here

      end

Menu Bars

When using a custom menu, Windows intercepts keyboard combinations using the
Alt and Ctrl keys, and the Mac OS intercepts keyboard combinations using the
Command key.

MouseUp Events
The mouseUp event is only sent to an editable field sprite if the field does not
have focus. See Chapter 9 for details.

Shockwave

Shockwave movies may not receive keyboard events until receiving focus via a
mouse click. Some developers add a "Click here to start" button to solve the
problem.
The browser may trap certain keyboard shortcuts, preventing those key combina-
tions from reaching your Lingo scripts. Avoid browser-specific keyboard shortcuts.

KeyCode Tester

You'll want your own keyboard tester to check the return values of idiosyncratic
keys not listed in this chapter or Appendix A (such as those with higher ASCII
values created using the Option or Alt keys). Attach this script to an editable
field sprite. It prints out the results in the Message window.

Example 10-14: Your Own KeyCode Tester
on keyDown

   put "key:" && the key
   put "keyCode:" && the keyCode
   pass
end

                                                                                Keyboard Tasks 299
Keyboard Tasks
        You may need to close the Message window before pressing keys, then open it
        afterward to see the results. You could get fancy and send the keyCode output to
        another field shown elsewhere on stage. Refer to the "Keyboard Lingo" Show Me
        in the online Help (or Macromedia's Web site), or download the keyboard tester
        from http://www.zeusprod.com/nutshell/examples.html.

      Keyboard Potential

        Don't overlook the potential to use your keyboard for good. Try implementing the
        following:
         Use the keyboard to set the volume (Hint: Use the soundLevel).
         Use keyboard shortcuts for custom menu options (see the "Menus" section of

              Chapter 14 in Director in a Nutshell).
         You can accept simultaneous input from multiple daisy-chained Macintosh

              ADB keyboards. Lingo can't tell which keyboard sent the event, so it is fun for
              collaboration, not gaming.
        Keyboard handling in Director is far from elegant, but this chapter has armed you
        with the knowledge to steer clear of many pitfalls. Refer frequently to the quirk list
        at http://www.updatestage.com/ because many keyboard idiosyncrasies encoun-
        tered are not the fault of your Lingo code.

        300 Chapter 10  Keyboard Events
         Chapter 12Behaviors, Parent Scripts                                           Behaviors,
                                                                                    Parent Scripts
                          CHAPTER 12

       Behaviors and Parent Scripts

The term Behavior is used loosely to describe several different types of Lingo
scripts. For now, think of Behaviors as score scripts that are easy to customize,
even by novices. Macromedia provides a slew of Behaviors under Xtras
Behavior Library. Refer to the Behaviors Show Me demo movie in the online
Help to learn the basics of applying existing Behaviors. See Chapter 5, Creating
Interactivity, in Macromedia's Using Director manual for an overview of the avail-
able Behaviors. Macromedia also provides numerous widgets (premade UI
components) and buttons that use Behaviors to create sprites with complex func-
tionality. See XtrasWidget WizardWidget Wizard and XtrasWidget
WizardButton Library. Refer to Chapter 14, Graphical User Interface Compo-
nents, in Director in a Nutshell for a detailed example of using premade widgets
and Behaviors.

            The Lingo Behavior Database is a collection of Behaviors main-
            tained by Renfield Kuroda at http://www.behaviors.com/lbd/.

Search the Macromedia site for Technote 08140 for possible ways to distribute
protected Behaviors. Refer to the downloadable examples (http://www.zeusprod.
com/nutshell/examples.html) for a detailed Behavior that simulates the Tempo
channel for use in Shockwave (which doesn't obey the Tempo settings).

What Is a Behavior?

The simplest (non-configurable) Behaviors are exactly like Director 5-style score
scripts attached to either a sprite or the script channel. To add a "beep-when-
clicked" Behavior to a sprite, you can use the simple script.

                                                    321
What Is a Behavior?

        Example 12-1: A Ludicrously Simple Behavior
         on mouseDown

             beep
         end

        Even such plain vanilla Director 5-style score scripts appear in the Behavior
        Inspector. For the remainder of this chapter the terms score script and Behavior
        will be used interchangeably.

                    Director 6 allows each sprite to have multiple Behaviors attached.
                    Although only one Behavior can be attached to each frame in the
                    script channel, you can attach an on exitFrame handler to a sprite
                    channel to emulate multiple frame scripts.

        Support for multiple scripts per sprite allows you to modularize your scripts into
        smaller pieces and attach more scripts as needed. For example, suppose two
        sprites have the same mouseEnter response but different mouseDown responses.
        You could attach the same on mouseEnter Behavior to both sprites and then add
        separate on mouseDown Behaviors to each. If their mouseDown responses are
        similar (perhaps differing only in the sound to be played on mouseDown), a single
        customizable Behavior could be written to handle mouseDown events for both
        sprites.
        A Behavior can be thought of as a score script with easily customizable attributes,
        such as which sound to play when an event occurs. They can also be thought of
        as Parent scripts attached to sprites. Behaviors are instantiated when the playback
        head enters the sprite span to which they are attached. The custom properties for
        each instance are stored with the Score data and read back at runtime.
        A Behavior's properties persist for the life of the sprite, and Behaviors can access
        any property of any other Behavior attached to the same sprite using:

                the property of sprite (the spriteNum of me)

      Creating Simple Behaviors

        The Behavior Inspector can be used as a simple Behavior Constructor. Refer again
        to Chapter 5 in Macromedia's Using Director and the Behaviors Show Me demo
        movie.

        Example 12-2: Writing Simple Scripts Via the Behavior Inspector

        To watch Director construct the script as you select Events and Actions to add:
           1. Open the Behavior Inspector using the "*" key on the numeric keypad or
              WindowInspectorsBehavior.
           2. Click the Edit Pane Expander (see Figure 12-1) to expand the editing pane.
           3. Select New Behavior from the Behavior popup, and name the Behavior.

        322 Chapter 12  Behaviors and Parent Scripts
                                                                                           What Is a Behavior?

Example 12-2: Writing Simple Scripts Via the Behavior Inspector (continued)
  4. Open the Script window using the Script button at the top of the Inspector.
  5. Use the Events popup and Actions popup to build your script.

Behavior                                        Parameter Button                            Behaviors,
Popup                                               Script Button                        Parent Scripts
                                                           Shuffle Down
Edit Pane
Expander                                                                   Shuffle Up
Vents                                                                    Attached
Popup                                                                    Behaviors

DescriptionPane                                                             Actions
Expander                                                                    Popup
                                                                            Editing
Lock                                                                        Pane
                                Current Sprite
                                                                            Description
                                                                            Pane

Figure 12-1: Behavior Inspector window

The Behavior Inspector doesn't create true "Behaviorized" scripts with all the
fancy attributes of Behaviors. It just helps novices to create basic score scripts
without typing in the Script window. A true Director 6-savvy Behavior usually has
user-defined properties and a minimal help string to explain its use.

Roy Pardi offers a Behavior Writer Xtra to ease some of the mechan-
ics of writing your own Behaviors. See http://www.tiac.net/users/
rpardi/behaviorwriter/.

Let's create a Behaviorized version of the beeping button script shown earlier.
When the Behavior--shown in Example 12-3 is attached to a sprite Director uses
the property list returned by ongetPropertyDescriptionList() to create a dialog (see
Figure 12-2) that lets the user customize the Behavior. From the dialog, the devel-
oper can choose which type of mouse event triggers the beep.

                                                What Is a Behavior? 323
What Is a Behavior?

Example 12-3: A simplified beeping Behavior

property whichEvent          then beep
on mouseUp me

   if whichEvent = #mouseUp
end

on mouseDown me
   if whichEvent = #mouseDown then beep

end

on mouseEnter me
   if whichEvent = #mouseEnter then beep

end

on getPropertyDescriptionList
   return [#whichEvent: [#comment: "Initializing Event:", 
                    #format: #symbol, 
                    #range: [#mouseUp, #mouseDown, #mouseEnter], 
                    #default: #MouseUp]]

end

Figure 12-2: Behavior parameter dialog

Even this simplified Behavior is much more complicated than a standard sprite
script, and it still just creates a beep! (Macromedia's Behavior Library includes an
even more complicated Sound Beep Behavior).
In this case, the dialog includes a pop-up menu with three possible values for the
whichEvent property (#mouseUp, #mouseDown, and #mouseEnter), as defined in
the #range attribute of the #whichEvent property. At runtime, the Behavior beeps
if the mouse event (such as mouseDown) matches the trigger event chosen for
whichEvent.
This may seem a poor candidate for a Behavior because it complicates a very
simple script. Behaviors, however, allow a novice to add customized behaviors
without Lingo scripting.

            Behaviors are sometimes hard to create and ugly to read, but easy to
            use.

324 Chapter 12  Behaviors and Parent Scripts
                                                                                           What Is a Behavior?   Behaviors,
                                                                                                              Parent Scripts
Using the Behavior Inspector

Apply existing Behaviors by dragging them from the Cast window to a sprite or
the script channel, or by using the Behavior Script popup in the Sprite Toolbar or
Sprite Inspector. A Behavior's scriptType of member property must be #score, not
#movie or #parent, or it will not appear in Behavior Inspector. If you open the
Behavior Library, its scripts show up in the Behavior popup, too.
Open the Behavior Inspector using the "*" key on the numeric keypad or Window
InspectorsBehavior.

            If ViewSprite OverlayShow Info is active, you can open the
            Behavior Inspector using the little green icon that appears next to
            the selected sprite on the Stage.

You can add your own Behavior Libraries to the ones under the Xtras menu, as
described in Chapter 4, CastLibs, Cast Members, and Sprites, in Director in a
Nutshell (add "Library" to the cast name and drop it in the Xtras folder).
If you are a novice using other people's Behaviors, set FilePreferences
EditorsBehaviors to edit scripts in the Behavior Inspector, the Script
window. See "Where the Hell Are My Scripts?" and Table 2-2 in Chapter 2, Events,
Messages, and Scripts.

Inside the Behavior Inspector
The Behavior Inspector is very malleable. Use the Edit Pane Expander and
Description Pane Expander buttons (see Figure 12-1) to customize it to your liking.
The Lock Selection button prevents the Behavior list from changing if the Score
selection changes.
The repertoire of Actions for automatic script construction is very limited, but it
gives you a basic feel for Lingo scripting. The Wait until Click or Key Press Action
creates incorrect Lingo code (puppetTempo -8), and should not be used.
When a Behavior is applied to a sprite or frame, you will be prompted to
customize its properties, if applicable.

            To change its properties after a Behavior has been attached to the
            Score, use the Parameter button in the Behavior Inspector.

To use the Parameter Button:
 Highight a sprite or frame with a Behavior attached, then highlight the desired

      Behavior in the Behavior Inspector.

                                                                          What Is a Behavior? 325
Objects of Mystery

         At least one property must be declared with the property keyword at the top
              of a Behavior script, or the Parameters button will be inactive.

         A Behavior must declare an on getPropertyDescriptionList handler, or the
              Parameters button will have no effect.

       Behavior Inspector Pitfalls

        Selecting the frame script channel and then creating a new Behavior using the
        Behavior Inspector will create a script in the cast, but it will not appear in the
        Score until dragged there. (If you highlight a sprite and create a Behavior, it will
        be attached automatically.)

        You can add Behaviors to multiple selected sprites. If multiple sprites are selected,
        deleting a Behavior via the Behavior inspector deletes it from only the first sprite
        selected. Choose Clear Script from the script popup in the Sprite Toolbar or Sprite
        Inspector to clear all scripts from multiple sprites.

        Behaviors and their properties persist only for the life of the sprite to which they
        are attached. Use global variables or parent scripts for more persistent data.

     Objects of Mystery

        Now that some of the mystery has been dispelled about Behaviors, let's discuss
        their cousins, parent scripts. I'll show you why, when, and how to use Object-
        Oriented Programming (OOP). Once you are introduced to the concepts, I'll then
        cover the terminology in more detail (refer also to the Glossary). Finally, I'll cover
        some practical examples. When you finish this chapter you'll realize that the
        "Great and Powerful Oz" is just some guy behind a curtain. So take a deep breath,
        repeat after me ("Parent scripts, child objects and Behaviors, oh my!"), and soon
        you'll be more at home with OOP than Dorothy was in Kansas.

        For a comparison of object-oriented Lingo with C++, refer to Table 4-1 in
        Chapter 4, Lingo Internals, and see the downloadable Chapter 20, Lingo for C
        Programmers. Read Chapter 12, Parent Scripts and Child Objects, in Macromedia's
        Learning Director manual for another perspective on object-oriented program-
        ming. Refer also to the Simple Child Object and Multiple Child Objects Show Me
        demo movies in the online Help.

      A Procedural Stopwatch

        Typical Lingo scripting is procedural because you create procedures (functions or
        handlers) to perform a particular task. For example, the average() function might
        average two numbers.

        Example 12-4: A Trivial Procedural Example

         on average a, b
               return (a+b)/2.0

         end

        If a script calls a procedure, the only communication between them is via the
        value returned by the function to caller.

        326 Chapter 12  Behaviors and Parent Scripts
                                                                                              Objects of Mystery   Behaviors,
                                                                                                                Parent Scripts
            A function is like a one-night stand. It has a fleeting existence and
            typically performs a single operation.

Let's create a stopwatch using a procedural approach. The code in Example 12-5
belongs in a movie script. We must use global variables to communicate between
the various functions and to maintain the current state of the timer. (This example
is heavily simplified and not very robust. See Example 11-9 for a robust object-
oriented version of this script.) Note that we used the name runTimer instead of
startTimer to prevent conflicts with the Lingo StartTimer command.

Example 12-5: A Procedural Stopwatch
global gCurrentTime, gStartTime
-- Reset the timer to 0
on resetTimer

   set gCurrentTime = 0
end resetTimer

-- Start the timer running
on runTimer

   set gStartTime = the ticks
end runTimer

-- Stop the timer (assumes timer was running)
on stopTimer

   set gCurrentTime = (the ticks - gStartTime)
end stopTimer

-- Report the timer's value (assumes timer is stopped)
on reportTimer

   return (gCurrentTime/60.0)
end reportTimer

We could use our stopwatch to check how long Lingo takes to print out the
numbers: from 1 to 100

      -- Test the timer functions
      on testTimer

          resetTimer
          runTimer
          repeat with x = 1 to 100

              put x
          end repeat
          stopTimer
          put reportTimer()
      end testTimer
This procedural approach is adequate for a single timer, but we would need to
create additional global variables to avoid conflicts between multiple timers.

                                                                             Objects of Mystery 327
Objects of Mystery

      Object-Oriented Programming

        Let's dive right in and create an object-oriented programming (OOP) version of
        our stopwatch. OOP is ideal because we can build a timer object (a reusable
        template), and create multiple instances (clones) of it that operate independently.
        Each instance can maintain its own properties, which are semi-private variables, as
        described in Chapter 1, How Lingo Thinks.

                    Lingo allows you to mix procedural and object-oriented program-
                    ming. Some people go overboard and turn everything into an object.
                    Use whatever is best for a given situation.

        An object (that is, a copy of a script) can contain several methods (handlers) to
        perform its desired actions. For example, a Timer object might behave like a stop-
        watch with four buttons (resetTimer, runTimer, stopTimer, and reportTimer), each
        implemented by a different method. An object's methods are stored in a template
        called a parent script. You don't ordinarily use the template directly; you use a
        copy or instance of the template in the form of a child object. This allows you to
        create multiple independent copies.

                    You can use parent scripts as semi-private code libraries without the
                    risks of naming conflicts associated with handlers in movie scripts. A
                    handler named StartTimer inside an object would not conflict with
                    the Lingo StartTimer command because they have differing scopes.
                    See "Handler Scope" in Chapter 2.

        Although unusual, instead of instantiating a parent script, you can access its
        handlers as:

                set variable = someHandler (script "ParentScript", args)
        You can even access a parent script's properties without instantiating it.

       The Life and Death of an Object
        The terminology required for objected-oriented programming can be summed up
        in a few sentences. Some of the terminology is redundant or used loosely. (Refer
        to the Glossary for complete definitions of each term used in this chapter.) Click
        your ruby slippers together as you repeat three times:

                    A parent script defines the properties (attributes) and methods (func-
                    tions) of an object. A child object is an instance (copy or clone) of
                    the parent script and is instantiated (created) using the new()
                    method. An object is disposed of when no variables refer to it.

        328 Chapter 12  Behaviors and Parent Scripts
                                                      Objects of Mystery

Let's look at all this in more detail.                                                   Behaviors,
                                                                                      Parent Scripts
Creating a Parent Script

Example 12-6: Creating a Child Object from a Parent Script

To create a child object from a parent script:
  1. Create a script cast member to hold the parent script (it is convenient to name
      the cast member, too). Use the popup in its cast member info window to set
      its type to Parent, or set its scriptType of member to #parent.
  2. Write the Lingo methods for the parent script as shown later. You'll need an
      on new method and other optional methods.
  3. In a separate script (or the Message window) instantiate (create an instance
      of) the parent script using the new() function, and store the instance in some
      variable.
  4. Use the instance (the child object) created above to call the other methods in
      the object. Because you specify the child object when calling other methods,
      Director knows which instance's properties and methods to use.

A Very Simple Parent Script

Here is a very simple parent script. It defines one property and only one method
(crying) besides the on new method.

                               private
                               property

property pCrying               default instantiation
                               method
on new me
   set pCrying = FALSE         script instance
   return me                   variable

end

on crying me

if pCrying then

     put "The baby is crying"

else                           custom method

     put "The baby is happy"

end if

end

Figure 12-3: Anatomy of a Parent script

If the on new handler is omitted, Director uses a default on new handler that just
returns the child object instance variable (me) such as:

      on new me
          return me

      end

If the earlier parent script is in a cast member named "Mommy," you can create
and manipulate a child object, such as shown in Example 12-7.

                                                      Objects of Mystery 329
Objects of Mystery

        Example 12-7: Instantiating and Using a Child Object
         set baby = new (script "Mommy")
         crying(baby)
         -- "The baby is happy"
         set the pCrying of baby = TRUE
         crying(baby)
         -- "The baby is crying"

        You can create as many children as you like, and each can have its own pCrying
        property.

                    If you don't store the returned child object instance (in this case, into
                    the variable baby) there is little point in instantiating the object
                    because you won't be able to refer to it later. In fact, it will be dis-
                    posed of immediately.

        Whereas a single child object instance may be stored in a global variable, related
        child object instances are commonly stored in global lists for later use:

                global gChildList
                if not listP(gChildList) then set gChildList = []
                addAt (gChildList, new (script "Mommy"))
        Using a single global list reduces the number of variables needed. Furthermore
        each instance can be used to access all the properties of each object.

      An Object-Oriented Stopwatch

        Here is an object-oriented version of the procedural stopwatch from Example 12-5.
        This Lingo should be placed in a parent script named "Timer." (See Example 11-9
        for a more robust timer object.)

        Example 12-8: An Object-Oriented Stopwatch
         property pCurrentTime, pStartTime

         on new me
             return me

         end

         -- Reset the timer to 0
         on resetTimer me

             set pCurrentTime = 0
         end resetTimer

         -- Start the timer running
         on runTimer me

             set pStartTime = the ticks
         end runTimer

         -- Stop the timer (assumes timer was running)

        330 Chapter 12  Behaviors and Parent Scripts
                                                                                              Objects of Mystery   Behaviors,
                                                                                                                Parent Scripts
Example 12-8: An Object-Oriented Stopwatch (continued)

on stopTimer me
   set pCurrentTime = (the ticks - pStartTime)

end stopTimer

-- Report the timer's value (assumes timer is stopped)
on reportTimer me

   return (pCurrentTime/60.0)
end reportTimer

Note these differences from the procedural version in Example 12-5:
 Property variables (beginning with the letter "p" for clarity) are used instead of

      global variables. Properties are declared with the keyword property, and can
      contain a different value for each instance of the object (that is, each timer). If
      we used globals, multiple timers would trample the values held in the globals.
 We added an on new method that will be used to instantiate the object.
 The variable me indicates the current instance of the child object. It is returned
      by new() when the child object is created and is typically stored in some vari-
      able by the caller. It is then used when calling other methods to identify the
      child object, so that Director can retrieve its properties rather than the proper-
      ties of some other instance.

We can test the Timer as shown in Example 12-9. It creates two separate instances
of the Timer object. The first one times the overall operation, and the second one
times the inner repeat loop.

Example 12-9: Testing a Timer Object

-- Test the Timer child object
on testTimerObj

   -- Instantiate two timers
   set timer1 = new (script "Timer")
   set timer2 = new (script "Timer")
   -- Start timer1 running
   resetTimer (timer1)
   runTimer (timer1)

   put "Testing the speed of the repeat loop"
   repeat with y = 1 to 10

       -- Start timer2 running
       resetTimer (timer2)
       runTimer (timer2)

       repeat with x = 1 to 1000
          set dummy = 5

       end repeat
       -- Pause and read timer2
       stopTimer (timer2)
       put "1000 Iterations took" && reportTimer(timer2) && "seconds"
   end repeat

                                                                             Objects of Mystery 331
Objects of Mystery

Example 12-9: Testing a Timer Object (continued)

   -- Pause and read timer1
   stopTimer (timer1)
   put "The whole test took" && reportTimer(timer1) && "seconds"
   -- Dispose of timer objects by setting them to zero
   set timer1 = 0
   set timer2 = 0
end testTimerObj

Note that we could instantiate dozens of timers without any conflicts or need for
multiple global variables. Each timer maintains its own set of properties.

I Gotta Be Me

Director uses the me variable to refer to a child object instance within the parent
script itself. See also "Script Instances" in Chapter 2.

Enter Example 12-10 this into a parent script called "Eden."

Example 12-10: Paradise Lost? Not as Lost as the Reader!

property pGender
property pName
property pKnowledge

on new me, gender, name

set pGender = gender

set pName           = name

set pKnowledge = FALSE

return me

end

on eatApple me
   set pKnowledge = TRUE

end

on getKnowledge me
   return pKnowledge

end

on ShowInfo me
   put pName && "is" && pGender

end

on GetName me
   return pName

end

on getGender me
   return pGender

end

on testKnowledge me
   if pKnowledge then

332 Chapter 12  Behaviors and Parent Scripts
                                                                                              Objects of Mystery   Behaviors,
                                                                                                                Parent Scripts
Example 12-10: Paradise Lost? Not as Lost as the Reader! (continued)
       put pName && "is banished"

   else
       put pName && "is innocent"

   end if
end

Test it in the Message window. Note that the arguments to the new() function call
are used to initialize properties for that particular object.

      set edenList = []
      add edenList, (script "Eden", #male, "Adam")
      add edenList, new (script "Eden", #female, "Eve")
When calling ShowInfo() we specify an object from our edenList:
      showInfo(getAt(edenList,1))
      -- "Adam is male"
      showInfo(getAt(edenList,2))
      -- "Eve is female"
When we call eatApple(), we again specify a child object instance. We need not be
aware what it does internally.
      eatApple (getAt(edenList,2))

      testKnowledge (getAt(edenList,1))
      -- Adam is innocent
      testKnowledge (getAt(edenList,2))
      -- Eve is banished
Notice that we indirectly set and accessed the pKnowledge property from outside
the parent script without even knowing it! The object handles the details for us!
One can access any property of an object from outside the object, using:
      put the property of object

            OOP purists will insist that you should never directly access a prop-
            erty of an object from outside the object. You should instead access
            them only via accessor methods, such as getName() and get-
            Gender() in Example 12-10.

An accessor method simply returns the value of a property of the object, allowing
us to write:

      getName (getAt(edenList,1))
      -- Adam
Thus we have not violated the encapsulation of the child object. The getName()
method can be changed without breaking any outside code. Any code that uses
the accessor method will continue to work.

                                                                             Objects of Mystery 333
Objects of Mystery

      Common Errors with Parent-Child Scripting

        There are several common errors you will surely commit.
        Omitting return me at the end of your on new handler:

              Without me, a child object instance will not be returned, and the caller will get
              a meaningless value.
        Omitting me when declaring other methods, such as on eatApple me:
              Without me, you won't be able to set a child object's properties, such as
              Knowledge from within the method.
        Not storing the child object instance returned by the new() call:
              Unless you store the return value, you won't be able to access the object later
              (in fact, the instance will be disposed of if nothing references it).
        Failing to assign values to the properties:
              You can either assign properties in the new() method or use a separate init()
              method to allow for reinitialization without reinstantiation.
        Trying to access a method within an object without first calling new():
              You generally should instantiate the object using new() before calling its other
              methods. New() accepts a parent script as the first argument. All other
              methods accept a child instance as the first argument, such as:
                set childObj = new (script "parentScript")
                someMethod (childObj)
              If you decline to instantiate the object first, as described in the tip under
              "Object-Oriented Programming" earlier in this chapter, you are manipulating
              the properties of the parent script itself, and not of a child object.
        Creating a parent script with type #movie:
              Lingo doesn't complain if your parent scripts are of type #movie, but the
              handlers in movie scripts have global scope, which can lead to conflicts or
              handlers being run unintentionally. If the parent script's type is #score, it will
              inadvertently appear in the script popup in the Sprite Toolbar. (Note that a
              Behavior's script type should be #score for this very reason.)

      When to Use Object-Oriented Programming

                    Parent scripts and child objects have the hallmarks of a long-term
                    relationship. Objects are created manually, tend to shun outsiders,
                    and persist until disposed.

        Parent-child scripting is generally a good idea to accomplish the following:

         Create objects that are defined by the current state of their properties, such as
              timers. An object remembers its own state (i.e., properties) and is therefore
              much easier to use and maintain without global variables.

         Create objects that persist over time or that require multiple operations. For
              example, the FileIO Xtra is just an object written in C. It allows you to manip-
              ulate external text files (via methods, just like a child object), including the

        334 Chapter 12  Behaviors and Parent Scripts
                                                                                              Objects of Mystery   Behaviors,
                                                                                                                Parent Scripts
      ability to open, read, write, delete, search, and close the file. The object keeps
      track of the properties, including the file's name and the location and the last
      position read within the file.
 Create code that is independent of other code. Objects are encapsulated
      (insulated) so that they can be developed separately from other code. Other
      Lingo primarily interacts with objects via the defined methods. Although this
      can simplify development and maintenance of some projects, it is not the
      panacea some people claim it to be.
 Create classes of objects in a hierarchy. Objects can inherit behaviors from
      ancestors, allowing you to create a tree of related objects. For example, a fam-
      ily tree of birds and reptiles may share a common ancestor that has an egg-
      Laying method.

            Two objects created from different Behaviors or parent scripts can
            both have methods of the same name that do completely different
            things.

You can send a single message to multiple objects without knowledge of their
internal operation. Each object will respond appropriately, allowing you to deal
with differing objects in a uniform way. Refer to "The ActorList" discussed later.

When to Use Behaviors

Behaviors are appropriate when you want a sprite or group of sprites to respond
to Director and user events in a certain way. They can be attached to the script
channel as well.

            Behaviors are like casual dating. A Behavior can be attached to mul-
            tiple sprite or frames, and a sprite can have multiple Behaviors
            attached. A Behavior is automatically associated with the sprite to
            which it is attached, and its lifespan coincides with that of the sprite
            span.

You should use Behaviors for multiple items with similar properties, such as
bouncing balls or space aliens. Although all instances of the object would be
intrinsically similar, they can have significantly different values for each property of
the object. For example, a ball's properties may include speed, acceleration, diam-
eter, mass, elasticity, and color. Example 8-14 is a sample Behavior that moves a
sprite along an elliptical path. The user can specify the foci and major and minor
axes of the ellipse.

Child Object References

When you create or use a child object, Director keeps track of how many refer-
ences there are to that object (how many things use it).

                                                                             Objects of Mystery 335
Objects of Mystery

        An object reference takes the form:
                <offspring "parentScriptName" referenceCount IDnumber>

        If you create an object without storing the return value, the referenceCount is
        just one (the object refers to itself long enough to print in the Message window).

        Example 12-11: Child Object References
                put new (script "parent script")
                -- <offspring "parent script" 1 27c252a>

        Because you made no record of the object, it will be disposed of at Director's
        whim. When you create an object and store the return value, Director increments
        the referenceCount to 2 because a variable now refers to it as well:

                set myChild = new (script "parent script")
                put myChild
                -- <offspring "parent script" 2 27c24f8>
        Note that a new IDnumber was assigned, and this object has no relation to the
        previously created object.
        Now assign a new variable to the existing object:
                set newVariable = myChild
                put myChild
                -- <offspring "parent script" 3 27c2548>
        Note that the referenceCount has increased, but the IDnumber has stayed the
        same. When you are done with an object, set any variables that use it to 0. When
        no variables or lists refer to an object, Director will dispose of it.
                set myChild = 0
                set newVariable = 0

        There is no built-in Lingo to determine the following at runtime:
         A list of objects that currently exist. You need to store the objects as you cre-

              ate them, usually in a list.
         A list of objects derived from a given parent script or the parent script of a

              given object.
         The number of variables that reference a given object, or what particular vari-

              ables reference a given object. Short of clearing all global variables, there is
              no way to clear references to a particular object to ensure that it is released.

                    You can create a root ancestor for all parent scripts that logs each
                    child object created. You would also explicitly call a destroy method
                    to remove the object from the global list.

        The unsupported UIHelper Xtra (included with D6.5's Save as Java Xtra) has two
        methods that read Behavior references and their property settings. These are
        unsupported:

        336 Chapter 12  Behaviors and Parent Scripts
                                                                                              Objects of Mystery   Behaviors,
                                                                                                                Parent Scripts
getBehaviorMemRef (spriteNum, nthBehaviorNum)
      The function returns the script member number of the nthBehaviorNum
      attached to spriteNum in the current frame.

getBehaviorInitializers (spriteNum, nthBehaviorNum)
      The function returns the user-specified values for the properties of the
      nthBehaviorNum attached to spriteNum in the current frame. These are the
      settings entered in the Parameters dialog created via getProperty-
      DescriptionList().

You can use an object's on new handler to set properties that may help track the
information previously discussed. For example, you could set a property called
pParent that contained the name of the parent script from which the object was
being created. You can also use the string() function to convert the object refer-
ence into a string, then try to parse that for the parent script name and
referenceCount: But the act of passing in the object reference and trying to parse it
increases the referenceCount.

            Avoid having an object refer to itself. An object with a property that
            contains a reference to the object itself will never be released from
            memory unless you specifically clear the property to "break the
            chain".

Child Object Properties

Although child objects themselves are not identical to property lists, the properties
of a child object can be extracted using the property list functions, such as
count(), getAt(), getPropAt(), and setaProp(). Refer to Example 12-10 and the read-
Props() utility in Example 6-19 of Chapter 6, Lists, that will extract an object's
properties.

Example 12-12: Reading Properties of Child Objects

set gAdam = new (script "Eden", #male, "Adam", FALSE)
readProps(gAdam)
-- "This #instance has 3 properties"
-- "#pGender: male"
-- "#pName: Adam"
-- "#pKnowledge: 0"

To determine the value of any property associated with any Behavior attached to a
sprite, you can use:

      put the property of sprite whichSprite
For example, assuming sprite 3 has the "Eden" script attached from Example 12-10:

      put the pName of sprite 3
      -- "Adam"
If more than one attached Behavior contains the same property, the value will be
returned for the first Behavior found with the specified property. If you want to

                                                                             Objects of Mystery 337
Behaviors versus Other Script Types

get a property of a specific Behavior, you can extract it from the scriptInstanceList,
which contains a list of attached Behavior script instances.

      put the pName of getAt (the scriptInstanceList of sprite 3, 2)
      -- "Eve"

You can use global variables instead of properties to create values that are
common across all instances of an object. Of course, the global will be universal
throughout the entire movie, as would any global.

Behaviors versus Other Script Types

Now that you understand a bit about objects, let's revisit Behaviors. Ironically,
Behaviors are most useful to users at opposite ends of the spectrum. Beginners
can use prewritten Behaviors without understanding their inner workings, and
experts can create their own powerful Behaviors. I'll assume you are somewhere
in between and that most of the Behaviors in the Behavior Library are too simple
for your needs, yet you have no idea how to construct your own Behavior or even
when you should try.

What Is a Behavior Script?

When I first used Behaviors I thought of them as parent (that is, object-oriented)
scripts tied to a sprite or frame. Now that I've used them for a while, I think of
them as instantiated score scripts. Table 12-1 shows some important differences
among these three types of scripts. For the purposes of this table, the term score
script refers to simple Director 5 style score scripts (In D6, a score script is a
Behavior is a score script.)

Table 12-1: Behaviors, Score Scripts, and Parent Scripts

                                               User-

                                               configurable Easy to

Type  Instantiated? Attached to Script Type Properties? Write?       Easy to Use?

Score Script Yes1        Sprite or   #score    No       Easiest      Medium
Behavior Yes1            Frame       #score    Usually  Hardest      Easiest

                         Sprite or
                         Frame

Parent Script Manually2  Nothing     #parent   No       Medium Hardest

1 All score scripts are instantiated automatically by Director 6 when the sprite or frame to which they are attached is encountered,
even though they might not have any properties.
2 Parent scripts are manually instantiated by the programmer using new().

Differences Among Behaviors, Sprite Scripts, and Frame Scripts

Behaviors are technically a type of score script. Like all score scripts, they are
treated as either frame scripts or sprite script depending on whether they are
attached to the script channel or a sprite channel. When designed to be attached

338 Chapter 12  Behaviors and Parent Scripts
                                                                        Behaviors versus Other Script Types   Behaviors,
                                                                                                           Parent Scripts
to a sprite, they predominantly respond to sprite-related events, such as mouseUp.
When designed to be attached to a frame, they predominantly respond to frame-
related events, such as exitFrame.

Differences Between Behaviors and Parent Scripts

Parent scripts and Behaviors are both object-oriented scripts. When a parent script
or Behavior is used, Director creates an instance of it, which can be thought of as
a copy, or clone, with its own set of values for each property (attribute).
Object-oriented means that the script acts as a template for a living, breathing
entity with a life of its own. When a parent script is instantiated, a new child
object is spawned. The child object owes it creation to the original parent script,
yet it operates independently from the parent script and from any other siblings
created from the same parent.

A Behavior is like a parent script that is used in the Score; it also has extra code to
create a dialog that allows a user to customize properties easily. When a Behavior
is encountered in the Score, Director creates a script instance that is analogous to
a child object.

            Behaviors are attached to either a sprite or a frame in the Score and
            created and disposed of automatically by Director when a sprite
            span begins or ends. They are initialized automatically by Director
            with the Parameters specified during authoring rather than via an on
            new handler.

Child objects of Parent scripts are created and disposed of manually by the
programmer and aren't tied to sprites or frames. The association between a
Behavior and the frame or sprite to which it is attached is automatic.

Use Behaviors to add some functionality to an entity in the Score. Suppose you
want to alert the user whenever they are inactive for five minutes. You can either
attach an appropriate timeout Behavior to the frame or to the sprite used as a
prompt. When the timeout occurs, change the sprite prompt or play an audio
warning.
Behaviors require the programmer to do more work, but the user to do less work.
When creating a Behavior, you must specify all the information that Director needs
to create a dialog box that prompts the user for the necessary properties.

Anatomy of a Behavior

Behaviors don't require anything beyond what is in any other sprite script or
frame script. A sprite Behavior may perform any initialization in an on beginSprite
handler and often traps mouse events using mouse handlers, such as on mouseUp.
Frame Behaviors also often perform any initialization in an on beginSprite handler
and do their remaining work in on exitFrame handlers. (Don't perform frame
initialization in a prepareFrame handler because it is called every frame.)

                                                       Behaviors versus Other Script Types 339
Behaviors versus Other Script Types

            Handlers in Behaviors automatically receive me (which contains a
            reference to the current script instance) as the first argument. Movie
            scripts and cast scripts are not instantiated, and their handlers don't
            receive me.

Behaviors often include getPropertyDescriptionList and getBehaviorDescription
methods. The optional runPropertyDialog method is less common.

            The getBehaviorDescription, getPropertyDescriptionList, and runProp-
            ertyDialog events are completely unlike standard Director events.
            They are not sent when the movie is playing, but they are sent when
            it is not playing. RunPropertyDialog and getPropertyDescriptionList
            can be called frequently when using the Behavior Inspector, and
            they can wreak havoc if they do not return a proper list. You should
            not set breakpoints in these handlers, as it is easy to create an infi-
            nite loop. They should call only built-in Lingo commands, and not
            custom handlers, because at compile time such handlers are not yet
            valid. You have been warned.

Table 12-2: Behavior-Related Event Handlers

Message                              Description
on getBehaviorDescription
on getPropertyDescriptionList        Called when the Behavior is highlighted in the Behavior Inspector. The
                                     return string appears in the bottom pane of the Behavior Inspector.
on runPropertyDialog
                                     Called when the script is compiled, attached to a sprite or frame, or the
                                     Parameters button is used in the Behavior Inspector. Also called to
                                     retrieve default parameters for use by on runPropertyDialog.

                                     Call whenever the Parameters dialog would be displayed. The default
                                     property values returned by on getPropertyDescriptionList are sent to the
                                     on runPropertyDialog handler, which can modify them to return a custom
                                     list of properties.

The GetBehaviorDescription Method

The on getBehaviorDescription method should return a text string describing the
Behavior. The Help message is displayed in the Description Pane of the Behavior
Inspector. It typically describes the parameters the Behavior accepts and specifies
whether it is intended as a sprite script or a frame script.

Example 12-13: The GetBehaviorDescription Method

on getBehaviorDescription me
   return "This is some help text"

end

340 Chapter 12  Behaviors and Parent Scripts
                                                                        Behaviors versus Other Script Types   Behaviors,
                                                                                                           Parent Scripts
The GetPropertyDescriptionList Method

Director uses the on getPropertyDescriptionList method to create a dialog box to
prompt the user for property settings. The method should return a property list of
only those properties that are user-settable for a given Behavior. For each prop-
erty, specify the property's name, followed by attributes that control its appearance
in the dialog box. Example 12-14 shows a sample property list with only one user-
settable property. (The #range attribute is optional and has two possible formats.)

Example 12-14: The GetPropertyDescriptionList Method

on getPropertyDescriptionList me
   set propList = [
     #propertyName: 
     [#comment: "user prompt", 
       #format: dataType, 
     {#range: [#min:minValue, #max:maxValue] |
                     [value1, value2, ...valuen], }
       #default: defaultValue] 
     ]
   return propList

end

#propertyName
      The name of the property variable that you want to let the user set. It should
      also be defined at the top of the Behavior script, using:

      property propertyName
#comment: "userPrompt"

      The text defined by #comment will appear in the dialog box presented to the
      user. Keep the text short and descriptive.
#format: dataType
      The #format entry tells Director what data type the user should be allowed to
      input. The allowed values are shown in Table 12-3.
#default: defaultValue
      The #default entry specifies an initial value for #propertyName and should
      be of the type specified by #format. The #default can be set to a variable's
      name that will be evaluated at runtime.
#range
      The optional #range entry can be either a linear list of enumerated values
      (which will appear as a pop-up menu) or a property list specifying a #min
      and #max range.

            The getPropertyDescriptionList example in Director's online Help
            does not document the #range entry. It is also missing a comma
            after #fieldNum in the line "addProp description, #field-
            Num,[#default:1,."

                                                       Behaviors versus Other Script Types 341
Behaviors versus Other Script Types

        The title of the Property dialog is set to the cast member name (or the cast
        member number if the name is EMPTY). Use a descriptive cast member name to
        remind yourself what the Behavior does.

        Because the Behavior parameters popup uses the MUI Xtra, it is beholden to the
        same limitations. You can fit only about 15 parameters on a 640-by-480 screen
        before the dialog fails to appear. See http://www.updatestage.com/previous/
        970801.html#item3 for details. A Behavior can have many properties, but the
        Parameters dialog may fail if more than 15 of those properties are specified in the
        list returned by on getPropertyDescriptionList. Implement a custom MUI dialog via
        the on runPropertyDialog handler if necessary (see the downloadable Chapter 21,
        Custom MUI Dialogs).

       The #format Code

        The #format of a property in the property description list determines how the user
        is prompted and what type of data he or she is allowed to enter. Table 12-3 and
        Table 12-4 show the #format codes that let you select from a pop-up list of items
        of the specified type, such as bitmap cast members, sound cast members, or
        marker labels. For example, if you are writing a Behavior that requires a sound,
        you might let the user pick that sound from a list of sound cast members by using
        a #format of #sound for the property of interest.

                    Using a #format such as #graphic that may encompass hundreds of
                    cast members will create a popup with hundreds of entries, taking
                    considerable time and possibly crashing the system.

Table 12-3: #format Codes for Cast Member Types

Message        Sent When
#format        Matching the type of member property
#bitmap        #bitmap cast members only
#button        #button cast members only
#digitalVideo  #digitalVideo cast members only (excludes #quickTimeMedia)
#field         #field cast members only (not #richText)
#filmLoop      #filmLoop cast members only
#graphic       #bitmap, #btned, #button, #digitalVideo, #field, #filmLoop, #movie, #ole, #picture,
               #PopMenu, #richText, #shape, #SWA (any cast member type that can be used in a sprite
#member        channel)
               all cast member types (those listed above for #graphic, plus #palette, #script, #sound,
#movie         and #transition)
               #movie cast members only (not movie scripts)

342 Chapter 12  Behaviors and Parent Scripts
                                                                  Behaviors versus Other Script Types

Table 12-3: #format Codes for Cast Member Types (continued)

Message      Sent When                                                                                                                  Behaviors,
#ole         #ole cast members only                                                                                                  Parent Scripts
#palette     built-in palettes, plus #palette cast members
#picture     #picture cast members only
#richText    #richText cast members only
#shape       #shape cast members only
#script      #script cast members only
#sound       #sound cast members only (not #SWA)
#transition  built-in transitions, plus #transition cast members

Note that getPropertyDescriptionList doesn't recognize #ActiveX, #btned, #flash,
#SWA, #quickTimeMedia, #text, or #xtra as separate cast member types.

Table 12-4 shows the #format options that don't pertain to a cast member types,
but rather to "pure" data types (floats, integers, Booleans, symbols, and strings)
and other Director entities (cursors, markers, and inks).

Table 12-4: Non-Castmember Behavior #format Codes

#format      User sees                       #default             #range

#boolean     Checkbox                        TRUE or FALSE        N/A
#cursor      Pop-up menu                     Installed cursors1   None or enumerated

#float       Entry field, slider, or pop-up 0.0 or your choice #min/#max, none, or linear list

             menu2

#ink         Pop-up menu                     Name of your choice None or enumerated

#integer     Entry field, slider, or pop-up  0 or your choice     #min/#max, none, or linear list
             menu2

#marker      Pop-up menu                     previous, loop,      previous, loop, next, plus
                                             and next             any custom marker labels
#string      Entry field or pop-up menu3
#symbol      Entry field or pop-up menu3     EMPTY or your choice None or linear list

                                             EMPTY or your choice None or linear list

1 List of available cursor resources varies between Mac and Windows, but may include Arrow, I-Beam. Crosshair, Crossbar, Watch,
Blank, Help, Finger, Hand, Closed Hand, No Drop Hand, Copy Closed Hand, Pencil, Eraser, Select, Bucket, Lasso, Dropper, Air
Brush, Zoom In, Zoom Out, Vertical Size, Horizontal Size, and Diagonal Size. List does not include custom 1-bit cast members
used as cursors (use #bitmap instead).
2 If a #min/#max #range is specified the user sees a slider. If a linear list is used for #range, the user sees a popup menu. If no
range is specified, the user sees a text entry field.
3 User sees entry field or popup menu depending on #range as per footnote 2.

                                             Behaviors versus Other Script Types 343
Behaviors versus Other Script Types

        Here is an example getPropertyDescriptionList() if you were to turn the Eden script
        from Example 12-10 into a Behavior.

        Example 12-15: Behaving Yourself in Paradise
         property pGender, pName, pKnowledge

         on eatApple me
             set pKnowledge = TRUE

         end

         on getPropertyDescriptionList me
             set propList = [[LC]
               #pGender:[#default: #male, #format: #symbol, 
                                   #comment: "Gender", #range:[#male, #female]], 
               #pName: [#default: EMPTY, #format: #string,
                                   #comment: "Person's Name"], 
               #pKnowledge: [#comment: "Tree of Knowledge", 
                                   #default: FALSE, #format: #boolean] 
             ]
             return propList

         end

                    The on getPropertyDescriptionList is called only at authoring time to
                    store the default properties for a Behavior. Those properties are
                    applied when the script is instantiated at runtime. Don't forget to
                    return the property list you've built.

       The RunPropertyDialog Method
        Despite its name, the on runPropertyDialog handler is never called at runtime. It is
        called only when a Behavior's Parameter dialog would otherwise appear during
        authoring. If present in a Behavior, the on runPropertyDialog handler is called to
        set values for the properties without prompting the user via the Parameter dialog.
        It receives a list of default values of the properties returned from on getPropertyDe-
        scriptionList. In Example 12-16, defaultProps is [#pGender: #male, #pName: "",
        #pKnowledge: 0] before the handler is called, and [#pGender: #male, #pName:
        "Seth", #pKnowledge: 0] afterwards.

        Example 12-16: The RunPropertyDialog Method
         on runPropertyDialog me, defaultProps

             set the pName of defaultProps = "Seth"
             return defaultProps
         end

        344 Chapter 12  Behaviors and Parent Scripts
                                                                        Behavior and Parent Script Lingo

          The Lingo Dictionary and online Help have incorrect entries for run-
          PropertyDialog.

Behavior and Parent Script Lingo                                                                                Behaviors,
                                                                                                             Parent Scripts
Table 12-5 covers Lingo pertaining to Behaviors and parent scripts.
The text of scripts is limited to 32,000 characters, so it easy to run out of room
when creating complex objects.
You can use the ancestor property to create objects that use multiple scripts, but
the management can get annoying. Hopefully, Macromedia will address the 32,000
characters scriptText of member limit in Director 7.

Table 12-5: Behaviors and Parent Scripts Lingo

Command                             Usage

the actorList                       A list of object instances that receive the stepFrame message. Use
                                    to send messages to child objects each time playback head moves.

ancestor                            A property of a child object that points, not to the parent script, but
                                    to a "grandparent" script of your choosing.

                                    property ancestor
                                    set ancestor = new (script "Ancestor Script")

birth (script "Parent Script")      Obsolete. Use new() instead.

call (#handlerName, script |        Sends a custom message to a one or more scripts, script instances,
scriptInstance | objectList {,      or child objects.
args})

callAncestor (#handlerName, script Sends a custom message to the ancestor of one or more script
| scriptInstance | objectList {, instances or child objects.
args})

the currentSpriteNum                Indicates the current sprite number from within a Behavior attached
                                    to a sprite.

getBehaviorInitializers(spriteNum,  Returns the list of default property values passed to on runProperty-
behaviorNum)                        Dialog. Requires UI Helper Xtra, included with D6.5.

getBehaviorMemRef(spriteNum,        Returns an absolute cast member reference of the specified
behaviorNum)                        behavior attached to spriteNum (or 0). Requires UI Helper Xtra,
                                    included with D6.5.

me                                  Identifies the current script instance. Returned by new() when the

                                    child object is created and used as a parameter to Behavior and

                                    object methods.

                                           Behavior and Parent Script Lingo 345
Behavior and Parent Script Lingo

Table 12-5: Behaviors and Parent Scripts Lingo (continued)

Command                           Usage

new()                             Used to create a new instance of a parent script or Behavior.

                                  set childObj = new (script "ParentScript" {,

                                  args...})

on getPropertyDescriptionList     Returns a property list defining all the user-settable properties of a
                                  Behavior. See Table 12-2.

on getBehaviorDescription         Returns a text string describing the Behavior, displayed in Behavior
                                  Inspector as Help text. See Table 12-2.

on new                            Handler called when a parent script is instantiated. Must return a
                                  script instance (me)

on runPropertyDialog              Changes Behavior's properties without user intervention. Suppresses
                                  Parameter dialog. See Table 12-2.

on stepFrame                      Handler to perform some action each time the stepFrame message
                                  is sent to the actorList.

property propertyVar              Defines a semi-private variable for a Behavior or parent script.

script "Parent" or script scriptNum Used with new() to refer to a Parent Script.

the scriptInstanceList of sprite  A list of Behavior instances attached to a given sprite. Available only
                                  while Director is running. See getBehaviorMemRef().

the scriptType of member          Script type should be set to #score for Behaviors and #parent for
                                  parent scripts.

send (object, #message)           Unsupported variant of call().

sendAllSprites (#message {, args}) Sends a message to all sprites in the current frame.

sendAncestor (object, #message) Unsupported variant of callAncestor().

sendSprite (whichSprite, #message Sends a message to a particular sprite in the current frame.
{, args})

the spriteNum of me               Indicates the current sprite number from within a Behavior attached
                                  to a sprite.

Handler Evaluation with Behaviors

New Sprite Events Sent to Behaviors Used as Sprite Scripts

See Chapter 2 for a full description of events. In Director 6, Score scripts attached
to the sprite channels now receive new, enterFrame, and exitFrame messages
(plus many other new messages). These handlers would not have been called
when playing in Director 5. The Director 6 CD includes a cleaner utility in the
Goodies\Movies\Cleaner folder, and D6.0.2 now warns about these when
updating from Director 5 movies. (See the Director 6 ReadMe file.)

346 Chapter 12  Behaviors and Parent Scripts
                                                                          Behavior and Parent Script Lingo   Behaviors,
                                                                                                          Parent Scripts
For backwards compatibility the Shockwave for D6 plug-in does not send enter-
Frame and exitFrame messages to sprites if the movie file being played is of pre-
Director 6 vintage. It does send the new message to sprites however.

Handler Execution, The ScriptInstanceList, and the SpriteNum of Me

As described in Example 2-11 in Chapter 2, the new event is sent to sprites before
the beginSprite event. If a Behavior defines an on new method, it is called before
the scriptInstanceList is populated with any Behavior instances, and before the
property values are assigned. Therefore, you can't manipulate the scriptInstan-
ceList or assume that Behavior properties have been defined in an on new handler.
If a score script is going to be used as both a sprite Behavior and instanced
explicitly via the new() function, then the on new handler should declare and set
the spriteNum of me property. (It is set automatically when an instance of the
script is created for a Behavior, but not if new() is called explicitly.
Refer to the Director 6 ReadMe and Director 6.0.1 Updates file for more details.

The ActorList

The stepFrame message is sent only to items in the actorList. In Director 6, sprites
receive prepareFrame, exitFrame, and enterFrame events, but the actorList can still
be used to notify Parent scripts and child objects (which don't receive events by
default) when the playback head moves. Refer to "The ActorList" in Chapter 2 for
more details. Note that each item on the actorList can have its own on stepFrame
handler to take appropriate action when the playback head advances.
The following can be used to add and remove items from the actorList.

Example 12-17: The ActorList

on addToActorList dummy, object
   -- only add objects to the actorList
   if not objectP(object) then
       alert "Not an object" && object
       exit
   end if
   -- Don't add it if it is already on the list
   if getPos (the actorList, object) = 0 then
       add the actorList, object
   end if

end addToActorList

on removeFromActorList dummy, object
   -- Remove the item from the actorList
   set offset = getPos (the actorList, object)
   if offset then
       deleteAt (the actorList, offset)
   end if

end removeFromActorList

                                                         Behavior and Parent Script Lingo 347
Behavior and Parent Script Lingo

                    See Example 1-34 under "Special Treatment of the First Argument
                    Passed" in Chapter 1 for details on why the above uses a dummy
                    parameter instead of passing object as the first parameter.

        The following uses the utilities in Example 12-17 cause a Behavior instance to
        automatically add its sprite to (and delete its sprite from) the actorList. The sprite
        will then receive stepFrame events.

                on beginSprite me
                    addToActorList (void, the spriteNum of me)

                end

                on endSprite me
                    removeFromActorList (void, the spriteNum of me)

                end
        To clear the actorList entirely, you can use deleteAll(the actorList) or simply set it
        to [].

                    The clearGlobals command also clears the actorList in D6, although
                    it didn't do so in D4 or D5.

      Adding Behaviors at Runtime

        The scriptInstanceList of sprite property is a Lingo list of instantiated Behaviors.
        Until the playback head enters the sprite of interest, the scriptInstanceList is the
        EMPTY list ([]). See "Script Instances" in Chapter 2 for details.
        You can't set the scriptInstanceList during authoring or even a Score Recording
        session because it is a list of instances, not script numbers. The scriptNum of sprite
        returns only the first attached Behavior, but you can use the getBehaviorMemRef()
        function included with the UI Helper Xtra (included with D6.5) to count the
        number of attached Behaviors and determine their member numbers.

        Example 12-18: Getting Attached Behaviors
         on getBehaviors spriteNum

             set n = 1
             set memList = [ ]
             repeat while (TRUE)

                 -- This requires the UI Helper Xtra
                 if getBehaviorMemRef (spriteNum, n) = 0 then

                    exit repeat
                 else

                    add memList, member getBehaviorMemRef (spriteNum, n)
                    set n = n + 1
                 end if

        348 Chapter 12  Behaviors and Parent Scripts
                                                                          Behavior and Parent Script Lingo   Behaviors,
Example 12-18: Getting Attached Behaviors (continued)                                                     Parent Scripts

   end repeat
   return memList
end getBehaviors
You can add Behaviors to a sprite at runtime by adding a script instances to its
scriptInstanceList (but only if at least one Behavior was already attached).
Example 12-19: Adding Behaviors At Runtime
set newBehavior = new(script"BehaviorScript" {, args})
add (the scriptInstanceList of sprite n, newBehavior)
Hopefully this chapter has dispelled the mysterious aura surrounding object-
oriented programming and Behaviors. You should have recognized the deep
parallels between programmer-defined objects and Director's built-in entities
(members, sprites, windows, lists, and so on). All such entities have properties that
can be manipulated without intimate knowledge of their internal structure.
Although some zealots create objects for everything, then create more objects to
manage their objects, I use OOP selectively. Develop your own style. Regardless
of your enthusiasm for OOP, you should add it to your arsenal. If you've under-
stood this chapter, you'll also understand that some tasks cry out for OOP.
Properly applied, it will make your code easier to write and more maintainable.

                                                         Behavior and Parent Script Lingo 349
