Adobe Flex 2 SDK Source Available
If you've got the Flex 2 SDK, then you've got the source; at least most of it. It's nothing new, but I don't think it's well known. The source can be found at [Flex SDK Install DIR]/frameworks/source. If you've never downloaded the SDK by itself and only use FlexBuilder, then you'll find the SDK under your FlexBuilder install directory.
I point this out because I've imported the source into FlexBuilder for easy reference and code navigation. If you're curious how the Flex team does something, then now you know.
Enjoy!






