How can I test if a given DisplayObject is obscured by any other DisplayObject on the same stage?

Question

I'm trying to write a function
    internal function isObscured(o: DisplayObject, p: DisplayObject): Boolean;
which tells whether the given object o is partially or completely obscured by the object p. I already tried using hitTestObject and hitTestPoint; the latter would actually do what I want if I tested every point in the bounding rectangle of the object at hand - not very efficient. I also tried using setChildIndex but it doesn't seem to help either since it's possible that an object isn't obscured even though it does not have the largest child index.
My current approach is to test whether any bounding rectangle of the objects with larger child indices than the object at hand intersects with the bounding rectangle of the object at hand, however I suspect that this will only work for testing whether any sibling overlaps my object. I also looked at the 'depth' property of UIComponent but it seemed from the same issue (the depth is relative among all siblings).
Does anybody know whether there's a better way to check whether a Flex control is obscured by another?

Answer 1

Some other alternatives for testing:
Use the rectangle approach you mentioned, just make sure you call localToGlobal() on each of the points (rectangle coordinates) before doing the check. That will make all of your comparisons happen in the stage's coordinate system rather than each display object's parent's coordinate system.
Another option that may work is DisplayObject.hitTestObject():
http://help.adobe.com/en_US/FlashPlatform/reference/actionscript/3/flash/display/DisplayOb ject.html#hitTestObject()
Finally, I found this  link that has a hitTestRect() method that may help you:
http://www.as3gamegears.com/misc/actionscript-toolkit/