[Mesa-dev] [PATCH 15/15] intel: Advertise multisample DRI2 configs on gen >= 6

[Eric Anholt]

Chad Versace <chad.versace at linux.intel.com> writes:
> +   /* Generate multisample configs.
> +    *
> +    * This loop breaks early, and hence is a no-op, on gen < 6.
> +    *
> +    * Multisample configs must follow the singlesample configs in order to
> +    * work around an X server bug present in 1.12. The X server chooses to
> +    * associate the first listed RGBA888-Z24S8 config, regardless of its
> +    * sample count, with the 32-bit depth visual used for compositing.
> +    *
> +    * Only doublebuffer configs with GLX_SWAP_UNDEFINED_OML behavior are
> +    * supported. Singlebuffer configs are not supported because that would
> +    * require that rendering be eventually written to the singlesample buffer
> +    * even if DRI2Flush is never called; yet we downsample to the singlesample
> +    * buffer only on DRI2Flush.  GLX_SWAP_COPY_OML is not supported because we
> +    * have no tests for its interaction with MSAA.
> +    */

We actually need to remove our claiming of GLX_SWAP_COPY_OML in general,
because pageflipping means that we don't actually support SWAP_COPY.  We
only do UNDEFINED.

I'd say instead "singlebuffer configs are not supported because nobody
wants them".  I think all you need is (pessimistically)
intel_downsample_for_dri2_flush in intel_flush_front() to make front
buffer rendering actually work, and it's a problem that exists even in a
doublebuffer config.

I think this concludes my review.  Great work!  I'm excited to see this
finally land.
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