[Mesa-dev] [PATCH 1/7] mesa: Add field gl_renderbuffer.Unwrapped

[Ian Romanick]

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On 06/16/2011 07:14 AM, Brian Paul wrote:
> On 06/15/2011 06:34 PM, Chad Versace wrote:
>> If a renderbuffer wraps multiple renderbuffers, then Unwrapped points to
>> the them.
>>
>> For example, if hardware requires separate depth and stencil buffers
>> (X8_Z24 and S8), then glRenderbufferStorage(GL_DEPTH24_STENCIL8) may
>> create a fake S8_Z24 renderbuffer for which Unwrapped[BUFFER_DEPTH] and
>> Unwrapped[BUFFER_STENCIL] point to the real X8_Z24 and S8 renderbuffers.
>>
>> Alter the following function to take Unwrapped into account:
>>      _mesa_framebuffer_renderbuffer
>>      _mesa_update_depth_buffer
>>      _mesa_update_stencil_buffer
>>      _mesa_reference_renderbuffer
> 
> Chad, could you give a bit of background on the big picture here?
> When/why do we need to represent separate depth and stencil buffers as a
> unified depth+stencil buffer?

We have future hardware that only does separate depth and stencil.
However, almost every existing application wants to use packed depth /
stencil.  Few apps have (tested) fallback paths.

> I'd like to move away from the whole renderbuffer/wrapper business. As I
> mentioned the other day, I'd like to move to a simple map/unmap model to
> accesss renderbuffer (and texture) data.  Mesa would generally see the
> buffers as-is without any kind of wrappers/converters.  If a driver
> needed to change the appearance of buffer(s) to core Mesa, it would have
> to do the data munging inside map()/unmap().  Would that approach work
> with the problem you're solving with unwrappers?
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