Create-ivity

haXe preloader

2 years ago I tried to create a preloader in haXe, but whatever I tried, nothing worked. Today, I had to create a preloader for a project at work. Needless to say, I wasn’t too happy, with that first experience in mind.

I did some Googling and found various forum and blog posts, but whatever I tried, nothing seemed to work. Mindless Labs suggested using mxmlc to embed the game .swf into an Actionscript preloader, but mxmlc couldn’t digest our game .swf. Game Haxe had another approach, but apparently that one broke when haXe 2.03 got released. Using the MochiAd preloader didn’t work out of the box either, because that one would only be run after the whole .swf was loaded. So I was thinking towards creating a separate preloader .swf that would load the main game .swf – it’s a messy, multi-file solution, but at least it’s a solution.

However, I talked about it to a coworker, asking how this would be done in ActionScript. The standard approach is to move all assets to a later frame, and to put some preloader code and assets in the first frame. I decided to give it a try – mind you, the same thing had failed me 2 years ago – and suprizingly, it worked! Back then, the assets had been inaccessible, but some haXe and swfmill versions later it works like a charm.

Here’s how my swfmill .xml file looks like now:

<?xml version="1.0" encoding="iso-8859-1" ?>
<movie version="9" width="600" height="400" framerate="30">
    <background color="#FFFFFF"/>
    <frame /> <!-- add one empty frame -->
    <frame>
        <library>
            <clip id='image' import='images/image.png' />
            <font name='font' import='fonts/font.ttf' />
        </library>
    </frame>
</movie>

Line 4 is important: it adds an empty frame, into which the haXe code is compiled. The second frame contains all the heavy-duty assets, which will be available once the whole .swf has been downloaded.

My main function now looks like this:

package ;
import flash.events.Event;
import flash.Lib;
import haxe.Log;
import game.Game;

class Main
{
    static function main()
    {
        Log.trace("Starting preloader");
        Lib.current.root.addEventListener(Event.ENTER_FRAME, onEnterFrame);
    }
    
    static function onEnterFrame(event : Event)
    {
        Log.trace("Downloaded " + Lib.current.root.loaderInfo.bytesLoaded + " of " + Lib.current.root.loaderInfo.bytesTotal + " bytes");
        
        if (Lib.current.root.loaderInfo.bytesLoaded >= Lib.current.root.loaderInfo.bytesTotal)
        {
            Lib.current.root.removeEventListener(Event.ENTER_FRAME, onEnterFrame);
            Log.trace("Preloading finished");
            
            // The Game class adds images to the screen, sets up listeners, etc.
            var gameInstance : Game = new Game();
        }
    }
}

I hope this post is useful to those who are looking for a haXe preloader. :)