[Mesa-dev] [RFC] [PATCH 1/2] mesa: let GL3 buf obj queries not depend on opengl major version

[Yuanhan Liu]

On Mon, Sep 19, 2011 at 09:17:42AM -0700, Ian Romanick wrote:
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> On 09/19/2011 07:20 AM, Brian Paul wrote:
> > On 09/19/2011 04:25 AM, Yuanhan Liu wrote:
> >> If I understand correctly, the new GL3 buffer object queries
> >> parameters, like BUFFER_MAP_ACCESS_FLAGS, depends on
> >> ARB_map_buffer_range extension.
> > 
> > That would make sense, but in fact the extension spec 
> > (http://www.opengl.org/registry/specs/ARB/map_buffer_range.txt)
> > says nothing about these queries.  They were added in GL 3.0.
> 
> It seems like this could be an error in the extension spec.  This is
> one of the extensions, like ARB_framebuffer_object, that "back ports"
> OpenGL 3.0 functionality to previous versions.  These extensions are
> supposed to provide *identical* functionality to OpenGL 3.0.  The
> other cases of mismatches have been determined to be bugs in the
> extension specs.
> 
> The question is, what do other implementations do?  The other other
> question is, are there any implementations that support
> ARB_map_buffer_range but not OpenGL 3.0?

If I understand your question correctly, the mesa is a such case.
Running glxinfo I would get a openGL with version 2.1 and
ARB_map_buffer_range extension supported.

But badly, the queries would depend on the OpenGL version instead of the
relative extension. It would get fault if we are going to query
somethings belongs to that extension. That's what the patch for.

Thanks,
Yuanhan Liu