I'm new to Flash and ActionScript, but managing quite nicely. One thing that is continuously getting in my way are the width and height properties of DisplayObject(Container)s. I'm finally starting to get my head around them and learned that the width and height of a Sprite are determined solely by their contents for example.

I do not understand the following though: I've got a Sprite that I add a bunch of Buttons to. The buttons all have a height of 30 and an y of 0. As such, I'd expect the height of the containing Sprite to be 30. Surprisingly, the height is 100.

The Adobe documentation of the height property of a DisplayObject states:

Indicates the height of the display object, in pixels. The height is calculated based on the bounds of the content of the display object.

Apparently, the 'bounds' of the object are important. So I went ahead and wrote this little test in the Sprite that contains the Buttons:

for (var i:int = 0; i < numChildren; ++i)
{
    trace("Y: " + getChildAt(i).y + " H: " + getChildAt(i).height);
    trace("BOUNDS H: " + getChildAt(i).getBounds(this).height);
}
trace("SCALEY: " + scaleY + " TOTAL HEIGHT: " + height);

This code iterates through all the objects that are added to its display list and shows their y, height and getBounds().height values. Surprisingly, the output is:

Y: 0 H: 30
BOUNDS H: 100
... (5x) 
SCALEY: 1 TOTAL HEIGHT: 100

This shows that the bounds of the buttons are actually larger than their height (and the height that they appear to be, visually). I have no clue why this is the case however. So my questions are:

• Why are the bounds of my buttons larger than their height?
• How can I set the bounds of my buttons so that my Sprite isn't larger than I'd expect it to be based on the position and size of the objects it contains?

By the way, the buttons are created as follows:

var control:Button = new Button();
control.setSize(90, 30);
addChild(control);