For what formats is this really needed? I think that usually if you have
a rgb surface, the corresponding rgbx format should be used instead of
rgba (which implicitly has the alpha == 1 property for blending). But
maybe some formats are missing...
Roland
Am 24.06.2016 um 04:07 schrieb Brian Paul:
> If the user requests an RGB drawing surface but we actually create an
> RGBA surface, we need it to act as if A=1. For blending, this means
> adjusting the blending terms to use 1/0 instead of DST_ALPHA/INV_DST_ALPHA.
> Drivers can use this flag to determine when that's needed.
>
> A previous patch I posted last year did this entirely in the state tracker
> but it involved making blend state dependent on the framebuffer state.
> This approach avoids that dependency.
> ---
> src/gallium/include/pipe/p_state.h | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/src/gallium/include/pipe/p_state.h
> b/src/gallium/include/pipe/p_state.h
> index 9c69355..8b0c3a2 100644
> --- a/src/gallium/include/pipe/p_state.h
> +++ b/src/gallium/include/pipe/p_state.h
> @@ -387,6 +387,7 @@ struct pipe_surface
> unsigned height; /**< logical height in pixels */
>
> unsigned writable:1; /**< writable shader resource */
> + unsigned alpha_one:1; /**< Should an RGBA surface should act like RGB?
> */
>
> union {
> struct {
>
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