Xgl support for GL_ARB_texture_compression (and more)

Matthias Hopf mhopf at suse.de
Tue Nov 14 03:22:05 PST 2006

On Nov 14, 06 10:52:28 +0100, Elias Naur wrote:
> I apologize if this has been asked before, or if it is already implemented. 
> While playing around with OpenGL in the stock SUSE 10.1 Xgl, I can't help but 
> notice that the advertised extension set and GL_VERSION is fixed (GL_VERSION 
> seem to be rewritten to "1.2 (<underlying driver version>)"), regardless of 
> the underlying driver's capabilities. This is annoying since I'd like support 
> for GL_ARB_texture_compression for my game Tribal Trouble, but I could 
> imagine that the general problem is larger (my card supports OpenGL 2.0, 
> including shaders, which I'm sure others would love to play around with in 
> Xgl).

This is a well-known issue. Xgl doesn't support GL or GLX above 1.2 yet.
Support for that just hasn't been written yet (especially getting GLX
1.3 support would be important, but needs a lot of additional tracking
code, e.g. for pBuffers).

> I know from private tinkering with the Xgl source that adding 
> ARB_texture_compression is easy (just a matter of tweaking an internal list 
> of extensions). I also know that you're using shaders internally to 
> accelerate video rendering. So my question is, why not expose these 
> extensions to GL clients?

... because nobody has written code for that yet?

Seriously, shader ids have to be tracked - just like texture objects -
for encapsulation. Also, shaders have to be enabled/disabled according
to the corrently active context. Additionally, you need to write
wrappers for the necessary functions. You probably have to update the
included Mesa as well, which could have side effects. That should be the
major issues, however, I could easily miss something important.


Matthias Hopf <mhopf at suse.de>       __        __   __
Maxfeldstr. 5 / 90409 Nuernberg    (_   | |  (_   |__         mat at mshopf.de
Phone +49-911-74053-715            __)  |_|  __)  |__  labs   www.mshopf.de

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