Thoughts on Flash

Building Flash/ActionScript sites entirely in code and using FireBug for debugging

Way back in the olden days I used to dabble in Flash for building dynamic websites. This was incredibly painful, as I recall, because I couldn't stand the Flash IDE. It was clunky and hard to navigate, there weren't enough key commands, and the code editor was a sad version of notepad at best. And why use Flash anyway? JavaScript will do most of what you need for a dynamic site nowadays and I believe things like Google AdSense read the DOM for content filtering, which would render a Flash site useless. For me, the answer was audio playback. I wanted to play some audio on a site and for this Flash seems like the only option.

Digging deep into my vault of web dabblery I remembered getting so fed up with the Flash IDE that I wrote an entire site in ActionScript alone. I was quite proud of this as it was an early foray into programming and made me realize how much I enjoyed writing software in code. By some stroke of luck, this ActionScript-only site written circa 2002 is still online! OK, the intro was made with some timeline animation (someone else did that) but everything else is pure code, I swear.

(UPDATE: Me an my big mouth: A few months after I wrote this article the site changed, it's not longer the 2002 version :( But it looks and behaves similar so they might have reused some of my code.)

So there I was, planning out my soon-to-blow-your-mind Flash audio player, yet without Creative Suite 3, the latest Flash IDE. In fact, I didn't want it — $699.00, ouch! Not to mention: the pain of installing another massive, bloated application on my hard drive. A little Googling around later, I discovered Motion-Twin ActionScript 2 Compiler, or mtasc for short, written in OCaml. This was exactly what I was hoping for, an open source command line tool for compiling ActionScript code into SWF (Flash) movies without the need for any clunky IDE. And it works very nicely.

Unfortanately, ActionScript seems to have no error handling whatsoever (or I haven't figured out how to handle errors yet) so doing stupid stuff like calling a method that doesn't exist will not stop program execution as it should. Great. So I quickly became familiar with hooks that mtasc provides to the trace() command. Calling trace() writes to the Flash IDE's debug log. But since you aren't in a Flash IDE when testing a freshly compiled swf, mtasc allows you to define your own implementation of trace. Cool! So naturally, I created my own trace that writes to the FireBug log. FireBug, of course, is the ultimate webapp-debugging tool.

Here it is first added to the example app (from the mtasc tutorial):

class Tuto {

    static var app : Tuto;

    function Tuto() {
        // creates a 'tf' TextField size 800x600 at pos 0,0
        // write some text into it = "Hello world !";
        trace("debugging with trace rocks!");

    // entry point
    static function main(mc) {
        // note that this seems to help mtasc find the trace method
        var f = new FireTrace();
        app = new Tuto();

...saved to And here is my trace implementation, saved to

class FireTrace {
    static function trace(msg, class_, file, line) {
        getURL('javascript:console.debug("[' + file + ':' + line + ' ' + class_ + '] ' + msg + '")');

I compiled it like so:

mtasc -swf Tuto.swf -trace FireTrace.trace -main -header 800:600:20

And used a simple HTML page to run it:

<script type="text/javascript">

if (!window.console || !console.firebug)
    var names = ["log", "debug", "info", "warn", "error", "assert", "dir", "dirxml",
    "group", "groupEnd", "time", "timeEnd", "count", "trace", "profile", "profileEnd"];

    window.console = {};
    for (var i = 0; i < names.length; ++i)
        window.console[names[i]] = function() {}

<object classid="clsid:d27cdb6e-ae6d-11cf-96b8-444553540000" name="TopPlayer" id="TopPlayer"
     width="800" height="600">
 <param name="movie" value="Tuto.swf"> 
 <param name="quality" value="high">
 <param name="loop" value="false">
 <param name="play" value="true">
 <!--<param name="bgcolor" value="#ffffff">-->
 <param name="swliveconnect" value="true">

 <embed src="Tuto.swf" quality="high" width="800" height="600"
 	type="application/x-shockwave-flash" name="TopPlayer" id="TopPlayer"

...and here is what it prints to my FireBug console:

[ Tuto::Tuto] debugging with trace rocks!

Notice that I had to add this line of code to the Tuto class:

var f = new FireTrace();

I don't know if this is a bug in mtasc but without it the custom trace seems like it never gets loaded. Also notice that I used the FireBug Lite JavaScript snippet for gracefully degrading console methods when FireBug isn't running.

After my romantic reunion with writing ActionScript, what has changed? The first thing I've noticed is that ActionScript 3 now looks exactly Java but I have no idea why. Luckily, it remains compatible with ActionScript 2 so you can leave out all the type declarations and everything still seems to work. Thus, it is pretty much a clone of JavaScript with some extra craziness you probably don't need. I'm still trying to figure out a better way to handle errors; putting debug statements everywhere is pretty lame. If anyone has a suggestion let me know. At the least, I would like to get an error in the log when I stupidly try to call a non-existant method.

Now that I have a prototype, the next step is to write automated tests, of course! This will be a lot of fun as I love watching tests pass. At first glance, the AsUnit (ActionScript Unit Test Runner) seems like it will be useful. I have no doubt that GUI testing Flash is no easier than it is in other languages, and thus not so easy to automate ... but one always needs unit tests.


Ah, looks like there is an even better way to call JavaScript by way of the ExternalInterface class:"console.log", variable1, variable2, variableN);

I haven't tried it but this article suggests to limit your calls to String, Number, Array, Object, and Boolean datatypes.

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