Posts tagged with “tips” and “debugging”

May 25, 10

Embedding Private Keys in SWF files

I've recently came across the new online SWF, Zend, and Java decomplier at that allows you to almost "view the source" of the SWF file online. If you had some important data stored in your SWF (such as API keys or passwords) you may not wish them being exposed.
The easiest (and therefore naïve) way to hide them* would be to store them in external text files and embed in the SWF.

[Embed(source="api_key.txt", mimeType="application/octet-stream")]
private const API_KEY:Class;

// ...

var myAPI_KEY:String = String(new API_KEY());

Then you can create an instance and cast it to String, like shown above.

The asset class extends mx.core.ByteArrayAsset and its byte content is not revealed by most decompilers.

*Of course, this "solution" does not offer any serious protection, you can still decompress the SWF and view the keys in the hex editor. You could scramble/hash them a bit to make the hacker's job harder but it's still possible to extract them.

12:46 PM | | 2 Comments | Tags: , ,
June 03, 09

A TextField called Dolly

I love Flash IDE. Especially the way you can stylise the TextField – decide what glyphs to embed and what fonts to include, set line height (leading), kerning (letterSpacing), colours, etc. I really hate creating new TextFields from scratch, entirely in code.

Using Library to store a TextField
Unfortunately, we can't store a TextField directly as a Flash IDE library symbol, so we have to wrap it up in a MovieClip and reference to it as follows:

var textFieldNormal:TextField = new TextMC().textTF;

where TextMC is the library MovieClip symbol containing a TextField named textTF.

How to duplicate (clone) a TextField?
You can't do it natively in AS3. But you can do some magic instead – clone all (excluding read-only) properties of another TextField.

var description:XML = describeType(referenceTextField);

for each (var item:XML in description.accessor)  
    // clone passed textfield properties that are not read only  
    if (item.@access != "readonly") targetTextField[item.@name] = referenceTextField[item.@name];  

targetTextField.defaultTextFormat = referenceTextField.getTextFormat();  

TextFormat of the referenceTextField won't be cloned with the loop above as it's not accessible via getter/setter/public methods. You have to clone it manually and this is what the last line does. It's very handy when you want to change the default kerning (letterSpacing) in Flash IDE and you want it to be preserved in your cloned text field.

I wrote a FixedTextField class that does that (plus fixes a couple of other TextField problems) – download zipped demo including the class.

01:00 PM | | 0 Comments | Tags: , , , , ,
May 12, 09

Finding the missing child

How many times you've encountered that annoying error ArgumentError: Error #2025: The supplied DisplayObject must be a child of the caller message?

It often happens when you're trying to remove a non-existing child which you would swear you had put there. How to find what depth is resides at, quickly? A simple "trace display list" package-level function closure traceDL(displayListElement, depth | "filter string") to the rescue!

    import flash.display.DisplayObjectContainer;
    import flash.display.DisplayObject;

    public function traceDL(container:DisplayObjectContainer, options:* = undefined, indentString:String = "", depth:int = 0, childAt:int = 0):void
        if (typeof options == "undefined") options = Number.POSITIVE_INFINITY;

        if (depth > options) return;

        const INDENT:String = "   ";
        var i:int = container.numChildren;

        while (i--)
            var child:DisplayObject = container.getChildAt(i);
            var output:String = indentString + (childAt++) + ": " + + " ➔ " + child;

            // debug alpha/visible properties
            output += "\t\talpha: " + child.alpha.toFixed(2) + "/" + child.visible;

            // debug x and y position
            output += ", @: (" + child.x + ", " + child.y + ")";

            // debug transform properties
            output += ", w: " + child.width + "px (" + child.scaleX.toFixed(2) + ")";
            output += ", h: " + child.height + "px (" + child.scaleY.toFixed(2) + ")"; 
            output += ", r: " + child.rotation.toFixed(1) + "°";

            if (typeof options == "number") trace(output);
                else if (typeof options == "string" && output.match(new RegExp(options, "gi")).length != 0)
                    trace(output, "in",, "➔", container);

            if (child is DisplayObjectContainer) traceDL(DisplayObjectContainer(child), options, indentString + INDENT, depth + 1);

So, where is my child?
With traceDL(someDisplayObject) you can reveal the whole display list of any DisplayObject. It will traverse its display list and show you all the instance names and types of the children (with depths they reside on), so it's easy to find out which depth your object hides. Some additional parameters like alpha, visibility, x and y coordinates, width and height (with scaling), and rotation will be displayed as well to help debugging (if it's too much, you can comment some of them out in the class file).

It's also possible to cut the traversing depth by specifying a number of levels to show: traceDL(someDisplayObject, 0) – will only show the first children, traceDL(someDisplayObject, 1) – will show you first children of someDisplayObject and also first children of its children.

Too many children shows up, it's like needle in the haystack!
No worries, just use traceDL(someDisplayObject, "filter string") where filter string is anything you think your child may contain, either it's an object's name, class (like MovieClip) or even some parameters (x: 100). Just anything that you think will match your child characteristics (that is what's outputted when you won't pass a search string).

Remember that if you hadn't explicitly set a name for a DisplayObject (either in code or Flash IDE), Flash player by default will call it instance and will assign a sequential number to it. Giving your object a name will always make it easier to identify.

I want to add a display object at a certain depth to a Library Symbol, but don't know the depth...
Nothing more perfect! With traceDL() it's childishly easy to trace any Library Symbol structure and determine what depth to use with addChildAt to dynamically add a DisplayObject to the Symbol.

Everything has slowed down!
The traceDL()function is recursive (unless you limit the depth it will dig till the last display node is scanned), and will use up a lot of your processor time, so take extra care and always remember to disable it in production code.

Erm, any demo/example usage?
Sure, there.

var rectangle:MovieClip = new MovieClip(); = "table";

var circle:Shape = new Shape();
circle.x = 100;
circle.y = 200;
circle.rotation = 45;
circle.scaleY = 0.5;

var square:Sprite = new Sprite(); = "square";
square.rotation = 45;
square.scaleX = 0.5;
square.scaleY = 2;

var someSprite:Sprite = new Sprite();


//0: instance4 ➔ [object Sprite]        alpha: 1.00/true, @: (0, 0), w: 0px (1.00), h: 0px (1.00), r: 0.0°
//1: table ➔ [object MovieClip]     alpha: 1.00/true, @: (0, 0), w: 0px (1.00), h: 0px (1.00), r: 0.0°
//   0: square ➔ [object Sprite]        alpha: 1.00/true, @: (0, 0), w: 0px (0.50), h: 0px (2.00), r: 45.0°
//   1: instance2 ➔ [object Shape]      alpha: 1.00/true, @: (100, 200), w: 0px (1.00), h: 0px (0.50), r: 45.0°

traceDL(this, "square");
//   0: square ➔ [object Sprite]        alpha: 1.00/true, @: (0, 0), w: 0px (0.50), h: 0px (2.00), r: 45.0° in table ➔ [object MovieClip]

traceDL(this, 0);
//0: instance4 ➔ [object Sprite]        alpha: 1.00/true, @: (0, 0), w: 0px (1.00), h: 0px (1.00), r: 0.0°
//1: table ➔ [object MovieClip]     alpha: 1.00/true, @: (0, 0), w: 0px (1.00), h: 0px (1.00), r: 0.0°

traceDL(rectangle, 1);
//0: square ➔ [object Sprite]       alpha: 1.00/true, @: (0, 0), w: 0px (0.50), h: 0px (2.00), r: 45.0°
//1: instance2 ➔ [object Shape]     alpha: 1.00/true, @: (100, 200), w: 0px (1.00), h: 0px (0.50), r: 45.0°

traceDL(this, "clip");
//1: table ➔ [object MovieClip]     alpha: 1.00/true, @: (0, 0), w: 0px (1.00), h: 0px (1.00), r: 0.0° in root1 ➔ [object MainTimeline]

traceDL(this, "shape");
//   1: instance2 ➔ [object Shape]      alpha: 1.00/true, @: (100, 200), w: 0px (1.00), h: 0px (0.50), r: 45.0° in table ➔ [object MovieClip]

If you were comfortable with AS2 "any depth" before and now feel a bit lost in AS3 depth management, traceDL() will definitely help you to switch.

You got me, I want it now!
Download the class

12:11 AM | | 10 Comments | Tags: , , ,