AS3 Child Index in relation to Stage - actionscript-3

Question

I m currently moving my CPU image post processing frame from AS2 to AS3. I used an array to handle all the objects that need to be rendered each frame.
I sort the array by the object's depth on _root, and then render them all onto one bitmapdata in order to draw them in the correct order.
In my AS3 game project I used displayobjectcontainers to handle "depths". for example I have multiple movieclips acting as containers on MovieClip(root), and then add the child to those movieclips to sort them. I also have other child containers inside those containers, forming an hierarchy.
But now I find it hard to sort the render list array because I cannot simply input an absolute "depth" value for the object. I use parent.getChildIndex, but this just gives me the index of the child in one of those containers.
Ofcourse you can make a big function and finally sort the array, but is there anyway to give the object's absolute index in relation to the root/stage?
Thanks a lot.

Answer 1

You could try something like this, which will start at a given DisplayObjectContainer and generate a list of all descendants in order of depth:
function collateChildren(container:DisplayObjectContainer):Vector.<DisplayObject>
{
var list:Vector.<DisplayObject> = new <DisplayObject>[];
for(var i:int = 0; i < container.numChildren; i++)
{
var child:DisplayObject = container.getChildAt(i);
if(child is DisplayObjectContainer && (child as DisplayObjectContainer).numChildren > 0)
{
// Target contains additional children.
list = list.concat(collateChildren(child as DisplayObjectContainer));
}
else
{
// Target is a child.
list.push(child);
}
}
return list;
}
This will not include children who contain other children, and can be used like:
var children:Vector.<DisplayObject> = collateChildren(stage);
trace(children);

Answer 2

A game world would consist of some layers,like role layer, map layer, and each layer has it's depth in the game world. When you try to add some displayobjects to the world, add the displayobjects to the targe layer.
At most time, the layer count won't be large, like 5 or 6. So you can draw the objects on each layer by layer depth.