This was going to be a question, but in writing I have discovered the answer. Take this example:
<?xml version="1.0" encoding="utf-8"?> <s:Application xmlns:fx="http://ns.adobe.com/mxml/2009" xmlns:s="library://ns.adobe.com/flex/spark" xmlns:mx="library://ns.adobe.com/flex/mx" minWidth="955" minHeight="600"> <s:Group height="50"> <s:BorderContainer height="100%"/> </s:Group> </s:Application>
You may be surprised to see that when rendered, the BorderContainer is larger than its parent despite being explicitly set at 100% height. 112 pixels to be precise.
Well, this is because BorderContainer's default properties include a minWidth and minHeight of 112 pixels, so if you want total flexibility, set these values to 0.
I hope others with the same infuriating problem will benefit from this post!
Thank you for this. You just solved a mystery for me!