[Xquartz-dev] GLX Updates in 2.4.0_aplha2

George Peter Staplin georgeps at xmission.com
Tue Jan 27 15:37:38 PST 2009

Quoted Jeremy Huddleston <jeremyhu at apple.com>:

> George has been putting together a new libGL for XQuartz that better
> supports the functionality available in OpenGL.framework (I think
> before we only supported OpenGL 1.2, and now it should be 2.0... is
> that correct, George?) as well as newer GLX versions (including pbuffer
> support).

The pbuffer support I wrote about was just a possible design for the  
Mac X11 libGL.  I think that design I wrote about will work for  
pbuffer support though.  It will support the intent of the pbuffer  
feature, but not the ability to get pbuffer events when the offscreen  
region is overwritten, because AFAIK that's not possible with the  
OpenGL framework that we base the X11 libGL on.  So you would have the  
fast offscreen rendering, but not the ability to know when it's been  
damaged, because as far as I know that's not a feature the OpenGL  
framework forces upon users.

The GLXPixmap code is going to need quite a few changes based on my  
research.  The existing code in the server and libGL isn't going to  
work from what I see.

> If you make use of GLX, I highly urge you to test out this new release
> and provide feedback.
> http://static.macosforge.org/xquartz/downloads/X11-2.4.0_alpha2.dmg
> Thanks,
> Jeremy

For what it's worth, the new libGL is good enough to run Pymol and  
many other apps (with and without GLX_STEREO), but there are some  
known issues I want to resolve.

1. the supported GLX extension strings are most likely incorrect,  
because some of the features don't work yet, such as GLXPixmaps and  
2. GLXPixmaps
3. GLXPbuffers

Thread support seems to be better. I can run the glthread demo and it  
works now, instead of working randomly.

Shared contexts seem to work better generally.  Though they need more testing.

Eventually I want to run the glean test suite with the new libGL,  
because I suspect that will find some issues.  Unfortunately the last  
few times I did that with the old X11 libGL it crashed the machine, so  
it's difficult to compare the old vs. the new in terms of test suite  
failures.  I think those underlying issues may be fixed now though.

Hopefully Jeremy has resolved the input system bugs in the 2.4.0  
releases.  I had some problems with input events not occurring, so the  
apps didn't respond to any button or key presses.


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