[Piglit] [PATCH] request RGB visual, fixes gbm rendering

Chad Versace chad.versace at intel.com
Tue May 12 11:39:24 PDT 2015

On Tue 12 May 2015, Emil Velikov wrote:
> On 9 May 2015 at 08:08, Ilia Mirkin <imirkin at alum.mit.edu> wrote:
> > GBM presumably defaults to RGB565 otherwise. Not all of these are
> > required, as some would still work with less precision, but this makes
> > the tests consistent. At least fp-formats and user-clip were failing
> > previously.
> >
> You're spot on - waffle gbm does default to RGB565 when the
> red/green/blue/alpha size is zero (the default values set in
> piglit_winsys_framework.c). Although I'm a bit baffled by the meaning
> of PIGLIT_GL_VISUAL_RGB - does it imply a 32bit and/or a red_size =
> green_size = blue_size(d) visual ?

PIGLIT_GL_VISUAL_RGB means "give me a config with at least 1 bit in each
of the r, g, and b channels". The backend (waffle, glut, whatever) then
interprets that as it wishes. It does not imply that the channels have
equal size.

I'm also baffled why, before Ilia's patch, gbm returns a RGB565 config,
but post-patch returns a RGB888 config. It suspect it's a quirk of
Mesa's gbm implementation.

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