Probable bug in WGL implementation (AIGLX) of GLX calls in XWin -wgl

[Tim Edwards]

Hello Cywgin-X developers:

    I have a tool I maintain called "magic", a VLSI layout editor.  One
of its nicer features is a graphics mode based on OpenGL.  Occasionally
I generate Cygwin versions of it, and was delighted to discover on my
last update of Cygwin that there is a support for hardware-accelerated
OpenGL using some translation between GLX and WGL calls at the level
of the X server.  I tried using this with my Cygwin version of magic,
and for the most part it works.  But it does have the strange effect
of overwriting the OpenGL window with contents of other windows.

    My setup is very non-standard but works under Linux and OS-X.  The
application is built as an extension of Tcl/Tk.  Because the application
makes all the OpenGL calls from C routines, it generates a generic
window using a call to Tk_CreateWindow(), and maps it using Tk_MapWindow().
The returned window is then passed to glXMakeCurrent().  All of this
works fine.

    The window that is used for the OpenGL rendering is framed by
scrollbars on the side and bottom that are "canvas" windows in Tk.
What I am seeing is that any time the scrollbars are redrawn, the
OpenGL window is over-drawn, looks like with the default Tk background
gray color.  A similar thing happens if I pop a window on top of the
OpenGL window;  when I pop it down, the image of the window remains
in the OpenGL window.  I presume that in the way GLX is supposed to
work, X11 has reserved pixmap space somewhere for the window, but
once the call to glXMakeCurrent() has been made, the contents of this
pixmap should not show up on the screen.  Yet that is what I am seeing.
Any clue as to what might be going on?

    One I tarball up this version of magic, I can send a pointer to
where it can be obtained if anybody wants to download it and test
for the bug.

					Thanks,
					Tim

+--------------------------------+-------------------------------------+
| Dr. R. Timothy Edwards (Tim)   | email: tim@opencircuitdesign.com    |
| Open Circuit Design, Inc.      | web:   http://opencircuitdesign.com |
| 22815 Timber Creek Lane        | phone: (301) 528-5030               |
| Clarksburg, MD 20871-4001      | cell:  (240) 401-0616               |
+--------------------------------+-------------------------------------+
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