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

[Brian Paul]

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?

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?

Thanks.

-Brian