http://java.net/jira/browse/MACOSX_PORT-693 submitted 2011/11/11 by Yuri Nesterenko
Run the attached example adapted from a test. Here InnerDropTargetPanel extends DropTargetPanel (which is a Panel). It (Inner one) has overridden all methods of DropTargetPanel necessary to implement DropTargetListener.
A smaller InnerDropTargetPanel is added to the top of a bigger DropTargetPanel. Look at the printout: all is OK with relative sizes of them, as reported.
Now, Robot (and later you may do it manually) drags from a bottom Button, and drag messages start coming immediately to the InnerDropTargetPanel even if it is nor reached yet. Even more, when you reach the InnerDropTargetPanel, it does receive DropExit. It's really bizarre.