[Mesa-dev] [PATCH] i965: set VIEWPORT_BOUNDS_RANGE value depending of the supported OpenGL version

[Samuel Iglesias Gonsálvez]

On Mon, Feb 29, 2016 at 04:33:42PM -0800, Kenneth Graunke wrote:
> On Friday, February 26, 2016 8:37:33 AM PST Samuel Iglesias Gonsálvez wrote:
> > From ARB_viewport_array spec:
> > 
> > " * On GL3-capable hardware the VIEWPORT_BOUNDS_RANGE should be at least
> >     [-16384, 16383].
> >   * On GL4-capable hardware the VIEWPORT_BOUNDS_RANGE should be at least
> >     [-32768, 32767]."
> > 
> > Signed-off-by: Samuel Iglesias Gonsálvez <siglesias at igalia.com>
> > ---
> >  src/mesa/drivers/dri/i965/brw_context.c | 13 +++++++++----
> >  1 file changed, 9 insertions(+), 4 deletions(-)
> > 
> > diff --git a/src/mesa/drivers/dri/i965/brw_context.c b/src/mesa/drivers/dri/
> i965/brw_context.c
> > index 31b6b2a..1569992 100644
> > --- a/src/mesa/drivers/dri/i965/brw_context.c
> > +++ b/src/mesa/drivers/dri/i965/brw_context.c
> > @@ -687,10 +687,15 @@ brw_initialize_context_constants(struct brw_context 
> *brw)
> >        ctx->Const.MaxViewports = GEN6_NUM_VIEWPORTS;
> >        ctx->Const.ViewportSubpixelBits = 0;
> >  
> > -      /* Cast to float before negating because MaxViewportWidth is 
> unsigned.
> > -       */
> > -      ctx->Const.ViewportBounds.Min = -(float)ctx->Const.MaxViewportWidth;
> > -      ctx->Const.ViewportBounds.Max = ctx->Const.MaxViewportWidth;
> > +      if (brw->intelScreen->driScrnPriv->max_gl_core_version >= 40) {
> > +         ctx->Const.ViewportBounds.Min = -32768;
> > +         ctx->Const.ViewportBounds.Max = 32767;
> > +      } else {
> > +         /* Cast to float before negating because MaxViewportWidth is 
> unsigned.
> > +          */
> > +         ctx->Const.ViewportBounds.Min = -(float)ctx-
> >Const.MaxViewportWidth;
> > +         ctx->Const.ViewportBounds.Max = ctx->Const.MaxViewportWidth;
> > +      }
> >     }
> >  
> >     /* ARB_gpu_shader5 */
> > 
> 
> Shouldn't we just support a 32k x 32k viewport?  In other words, change
> MaxViewportWidth/MaxViewportHeight?
> 

Good question. I looked for the HW limitations for Viewport's width
and heigh but I couldn't find the reference in the PRMs, just that
it is a 32 bits float. I ran piglit with 32k x 32k viewport in ILK
and BDW and there is no regressions. But as I didn't know if piglit is
testing it correctly, I prefered to keep it unchanged. Nevertheless, I
am open to do this change.

If you agree, I will write a patch that sets MaxViewportWidth and 
MaxViewportHeight to 32k.

Sam
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