Jframe (and probably Frame) enter/exit events are severely broken in
beta4 (they were better, but not perfect, in beta3). They are often
not generated at all (either enter or exit), and when they are generated
the boundary of the region that causes the event is not the bbox of
the Frame. *sometimes* is appears to be the ContentPane of the JFrame,
sometimes it appears to be a little larger and includes the JMenu at
the top. At no time does it ever include the entire window frame,
which it should.