[Mesa-dev] [PATCH 1/4] gallium: add pipe_surface::alpha_one field

[Roland Scheidegger]

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 {
>