[Mesa-dev] [PATCH 1/2] swrast: Fix fastpaths in glRead/WritePixels(GL_DEPTH_STENCIL)

[Eric Anholt]

On Mon, 10 Oct 2011 18:10:59 -0700, Chad Versace <chad at chad-versace.us> wrote:
> For glReadPixels, the user supplied pixels have format
> GL_UNSIGNED_INT_24_8.  But, when the depthstencil buffer's format was
> MESA_FORMAT_S8_Z24, the fastpath read from the buffer without reordering
> the depth and stencil bits. To fix this, this patch just skips the
> fastpath when the format is not MESA_FORMAT_Z24_S8.
> 
> The problem and fix for glWritePixels is analagous.
> 
> Fixes the Piglit tests below on i965/gen6 and causes no regressions.
>    general/depthstencil-default_fb-drawpixels-24_8
>    general/depthstencil-default_fb-readpixels-24_8
>    EXT_packed_depth_stencil/fbo-depthstencil-GL_DEPTH24_STENCIL8-drawpixels-24_8
>    EXT_packed_depth_stencil/fbo-depthstencil-GL_DEPTH24_STENCIL8-readpixels-24_8
> 
> Signed-off-by: Chad Versace <chad at chad-versace.us>

This code is all ridiculous -- while this fixes the problem, the real
issue is that GetRow is returning GL_UNSIGNED_INT_24_8 data whose
ordering actually depends on the underlying renderbuffer format.  That's
not how I understand GetRow is supposed to work.

But we all hate GetRow and friends, I think, so I've started on a branch
doing to renderbuffers what was done to textures with MapTextureImage.
It's in the rbmap branch of my Mesa tree.  Non-intel swrast users are
broken by it for now.

(This is mainly a heads-up for the folks who weren't in idr's basement
today when I started working on this)
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