Xgl server

[Matthias Hopf]

> > > and compared to the Xnest server, Xglx must always run on top of all 
> > > other windows as the back buffer is used for pixmap memory.
> > 
> > I didn't see the connection between these two things, so I whipped up a
> > patc88h that handles Expose events. Now this might be a horrible way of
> > doing it, in which case I'd appreciate an appropriate clue bat being
> > applied to me. :) I certainly prefer this over not handling exposures at
> > all though.
> 
> If I'm not mistaken, GLX doesn't ensure that the contents of the back
> buffer is unmodified when the window is covered by another window. This
> means that as the back buffer is used for pixmaps, exposures might
> destroy pixmap content.

For instance (old) sgi machines store the backbuffer in additional bits
of the framebuffer (you happened to have something like 1024 bpp visuals
on sgi's infinite reality 3 for double buffer active stereo multisample
12 bit-per-color visuals with window ids). If the window is covered by
another OpenGL window, these buffers are destroyed, of course.
At least the overlapping part.

Matthias

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