All current windowing platforms support Shaping a top level window.
java.awt.Window needs to support the ability to setShape so that the top
level window shape can be controlled. Windows has supported this API for
a very long time and X11 has the Shape extension to do this. Ofcourse
the API should also be able to query if the platform does support the
Shape functionality (in case Shape extension is not present, probably
very unlinkely, I have not seen any X-Server that does not have this).

Heavyweight components should be able to set their shape (atleast internal
to AWT). This is necessary to implement HW/LW mixing.

I have already prototyped a simple implementation of this API. Attached are the
webrevs for this prototype. It is part of the HW/LW mixing project we did.

Attached is a PDF file with the X11 Shape documentation :
http://www.xfree86.org/current/shapelib.pdf

As you can see this API has been in existence since 1989 !

Below is Win32 doc for SetWindowRgn :

http://msdn.microsoft.com/library/default.asp?url=/library/en-us/gdi/pantdraw_2him.asp


Attached is also a cool example of using the Shape extension (this worked
with my prototype.)

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