There are some things that will never appear in the Flash MX manual -- phrases like "to take advantage of this unsupported feature" and "to work around this bug in the software". Confined to the underground, these timesaving techniques become the tricks of the trade, swapped under the dim glow of desk lamps across the country. Not your desk lamp, perhaps, but that's what we're here for.

MOVIE CONSTRUCTION

Batten down those bitmap images

One of the longstanding bugs in Flash Player is commonly known as "bitmap shift". As bugs go it is somewhat unpredictable and difficult to reproduce, but it tends to show up whenever bitmapped images are being animated. The effect itself is akin to warping, and is best described as "hey, it moved without changing position."

There are several solutions to the bitmap-shifting problem, the most popular being to keep the alpha property of the affected graphics to 99%, so that they are never unanimated. A more recent trick is to create a large, empty transparent PNG image with a single pixel of colour in the top left-hand corner. Make it large enough to cover the stage, import the image and then move it to -1, -1 so that the single pixel is not visible. Place this image on the top layer of the main timeline, and the shifting effect goes away as long as the PNG is present.

Choose an optimum frame rate

Flash Player 4 had a maximum achievable frame rate of 18 frames per second. Versions 5 and 6 will attempt to play back at faster rates, whenever possible, but taking things too far can result in excess consumption of system resources, and slower overall performance. A frame rate of 31 will provide good cross-platform performance on newer machines. If you don't need extra smooth animation, throttle it back to 18.

Secure your files, for real

Security in Flash Player movies is inherently weak. You can write password authorisation routines in ActionScript, but this script is easily viewable in any hex or text editor. A new and highly effective freeware product named Tevas (http://www.genable.com/aso/tevas.html) seeks out references to passwords and keys you want to be secure, and replaces that part of the SWF with an encrypted version.

Tevas also performs a certain amount of "obfuscation" on the rest of your ActionScript code, making it difficult for decompiler programs such as Burak's ActionScript Viewer to extract script from your movies. This is particularly useful for sensitive or expensive-to-produce projects.

SCRIPTING

Use goto actions between scenes

This is an oldie but a goodie. Although goto actions can be used to navigate between scenes on the main timeline, scene change actions do not work from within movie clip symbols. This can be overcome by assigning frame labels to the first frame of each scene you want to target.

For simplicity, use labels that match the name of each scene. As an example, if you have scenes named Intro, Main and Catalog, assign the frame labels "Intro", "Main" and "Catalog." That way, no matter whether you're scripting the main timeline or a movie clip, you can use goto actions such as this:

_root.gotoAndStop("Intro");

Note that _root refers to the main timeline, regardless of where you place the code. When using multiple levels, replace _root with _levelx, where x is the appropriate level number.

Access plain text from files and server applications

The latest iteration of ActionScript takes the loadVariables() action and supersedes it with the much more flexible loadVars object. One of the hidden advantages of loadVars is that it draws on many of the same underlying methods as the XML object. loadVars is used to load text data written in URL-encoded variable pairs, like so: var1=hello&var2=goodbye. But what if you just want to load the contents of a simple text file or database field and place them into a text field? Here's how:

myText = new loadVars();
myText.onData = function(fileContents) {
textField1.text = fileContents;
};

By using the undocumented onData method of loadVars and hijacking it with a custom function, it's possible to intercept the text content before it goes for the usual parsing. So you end up with the raw, plain text.

Refer to attached/created/duplicated movie clips

Flash MX offers several ways to create movie clip instances on the fly. This is handy any time you have repeated elements, whether they are part of an interface or an animation. When using attachMovie(), createEmptyMovieClip() or duplicateMovieClip(), you'll often need to perform operations on the new instances, such as setting position properties or variables. In Flash MX all three of these actions return a reference to the new instance, which you can store in a variable. For example:

var tempMC = duplicateMovieClip("MC", "MC1", 1);
tempMC._x = 100;
tempMC._y = 100;
delete tempMC;

The local variable tempMC automatically points to the duplicate movie clip, regardless of where it is in the movie. The script shows it can be deleted when no longer in use.

Attach imported symbols

Symbol linkage is a great feature. It allows you to share assets between multiple movies, saving on bandwidth and editing time. But what happens when you want to attachMovie() a symbol that's already being imported at runtime? Usually it isn't possible, because a symbol with its linkage set to Import cannot simultaneously be set to Export for ActionScript.

There is a way around this. Simply drag an instance of the particular symbol onto the stage, and use the Convert to Symbol command to embed it into a new movie clip symbol. This is the clever bit: by setting the wrapper to Export for ActionScript, the instance contained within is still imported as before. You get the best of both worlds.

Import components

A similar but altogether different issue is the importing of shared components. Flash MX components are tricky things; they're complex and involve a lot of exporting for ActionScript and dynamic symbol attachment as it is. With so many interdependent elements, it's not possible to simply set, say, the ListBox component to Export for runtime sharing, and have everything work as expected.

The wrapping technique comes in handy here also. To share a component, drag an instance of it onto the stage, then wrap it in a new movie clip and set that to Export for runtime sharing, specifying the import URL as required.

Build dynamic paths with array access operators

In scripted applications, you'll often need to refer to a variable or object in a generic way, since its exact name won't be known until the movie is playing. This is common in games and other applications relying on external data or user input. A sly method of constructing dynamic references is to use array access operators. You can access the contents of any movie clip using this method; the clip's child objects and variables act like a named array. Here's an example:

for (i = 0; i < 5; i ++) {
_root["sprite" + i]._alpha = 50;
}

In the script above, the movie clips in the main timeline (sprite0 -- sprite4) have alpha properties set to 50%. In cases where you want to address all objects in a timeline, you can also use a number (rather than a named) index, such as _root[i].

PRODUCTIVITY

Quickly restore panels in Mac OS X

A major bug in the Mac OS X version of Flash MX is the application's tendency to "lose" user interface elements like the Toolbox and Panels. Rather than having to manually go to the Window menu and re-activate necessary panels, create a keyboard shortcut for the Default panel set. That way when things disappear, it's only a quick key press to solve the problem.

To make a keyboard shortcut in Mac OS X, go to the Flash MX application menu and choose Keyboard Shortcuts. Duplicate the current set, and then scroll down to Window, Panels, Default set in the command list. Then use the lower area of the dialog to assign a shortcut, such as Shift+Cmd 1.