[Mesa-dev] Conflicts between OES/EXT/ARB_framebuffer_object and GL3.0/GLES2

[Chad Versace]

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On 05/03/2012 10:33 AM, Eric Anholt wrote:
> On Wed, 02 May 2012 18:32:01 -0700, Chad Versace <chad.versace at linux.intel.com> wrote:
>> Solutions for core Mesa
>> -----------------------
>>
>> As for fixing _mesa_BindFramebufferEXT, I have two ideas.
>>
>> 1. Enforce in _mesa_BindFramebufferEXT that no more than one of ARB_fbo
>>    and EXT_fbo is enabled, then clean up its validation logic. This is
>>    a big hammer, and, if done right, can eliminate any ambiguities in behavior.
>>    (FYI, if I understand the gallium code, the only drivers that currently
>>    enable both are Intel, swrast, and OSMesa).
>>
>> 2. Create separate entry points:
>>       - _mesa_BindFramebufferEXT, which implements
>>           - glBindFramebufferEXT
>>           - glBindFramebufferOES
>>           - glBindFramebuffer in GLES2
>>       - _mesa_BindFramebufferARB, which implements
>>           - glBindFramebufferARB
>>           - glBindFramebuffer in GL 3.x
> 
> 3. Just change this hunk of _msea_BindFramebufferEXT:
> 
>       else if (!newDrawFb && ctx->Extensions.ARB_framebuffer_object) {
>          /* All FBO IDs must be Gen'd */
>          _mesa_error(ctx, GL_INVALID_OPERATION, "glBindFramebuffer(buffer)");
>          return;
>       }
> 
> to just not throw the error if EXT_fbo or if the API is ES2?

I don't believe 3 will work.

Suppose we are in a GL3.x context with EXT_fbo advertised.
Once the execution path has entered _mesa_BindFramebufferEXT, it is not possible to know
if the client called glBindFramebuffer (which has ARB_fbo semantics) or called
glBindFramebufferEXT, yet the two functions have different behavior. As far as I can tell,
the only way to give the functions different behavior is create separate API entry points.

- ----
Chad Versace
chad.versace at linux.intel.com
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