[Mesa-dev] [PATCH] st/xa: Fixups for PIPE_FORMAT_R8_UNORM A8 usage v2.

[Jose Fonseca]

On 17/09/15 13:24, Thomas Hellstrom wrote:
> Check for PIPE_FORMAT_R8_UNORM when setting up the copy shader.
> Also re-enable the dest alpha blending with A8 destination that
> actually turned out to be correct.
>
> Verified using rendercheck that the composite operators
> overreverse, in, out, atop, atopreverse and xor seem to work fine
> with a8 destiation.
>
> v2: Fix a copy-paste error.
>
> Reported-by: Jose Fonseca <jfonseca at vmware.com>
> Signed-off-by: Thomas Hellstrom <thellstrom at vmware.com>
> ---
>   src/gallium/state_trackers/xa/xa_composite.c | 34 ++++++++++++++++++++--------
>   src/gallium/state_trackers/xa/xa_renderer.c  |  6 +++--
>   2 files changed, 29 insertions(+), 11 deletions(-)
>
> diff --git a/src/gallium/state_trackers/xa/xa_composite.c b/src/gallium/state_trackers/xa/xa_composite.c
> index e81eeba..bcb27ea 100644
> --- a/src/gallium/state_trackers/xa/xa_composite.c
> +++ b/src/gallium/state_trackers/xa/xa_composite.c
> @@ -78,6 +78,27 @@ static const struct xa_composite_blend xa_blends[] = {
>         0, 0, PIPE_BLENDFACTOR_ONE, PIPE_BLENDFACTOR_ONE},
>   };
>
> +/*
> + * The alpha value stored in a L8 texture is read by the
> + * hardware as color, and R8 is read as red. The source alpha value
> + * at the end of the fragment shader is stored in all color channels,
> + * so the correct approach is to blend using DST_COLOR instead of
> + * DST_ALPHA and then output any color channel (L8) or the red channel (R8).
> + */
> +static unsigned
> +xa_convert_blend_for_luminance(unsigned factor)
> +{
> +    switch(factor) {
> +    case PIPE_BLENDFACTOR_DST_ALPHA:
> +	return PIPE_BLENDFACTOR_DST_COLOR;
> +    case PIPE_BLENDFACTOR_INV_DST_ALPHA:
> +	return PIPE_BLENDFACTOR_INV_DST_COLOR;
> +    default:
> +	break;
> +    }
> +    return factor;
> +}
> +
>   static boolean
>   blend_for_op(struct xa_composite_blend *blend,
>   	     enum xa_composite_op op,
> @@ -111,16 +132,11 @@ blend_for_op(struct xa_composite_blend *blend,
>       if (!dst_pic->srf)
>   	return supported;
>
> -    /*
> -     * None of the hardware formats we might use for dst A8 are
> -     * suitable for dst_alpha blending, since they present the
> -     * alpha channel either in all color channels (L8_UNORM) or
> -     * in the red channel only (R8_UNORM)
> -     */
>       if ((dst_pic->srf->tex->format == PIPE_FORMAT_L8_UNORM ||
> -         dst_pic->srf->tex->format == PIPE_FORMAT_R8_UNORM) &&
> -        blend->alpha_dst)
> -        return FALSE;
> +         dst_pic->srf->tex->format == PIPE_FORMAT_R8_UNORM)) {
> +        blend->rgb_src = xa_convert_blend_for_luminance(blend->rgb_src);
> +        blend->rgb_dst = xa_convert_blend_for_luminance(blend->rgb_dst);
> +    }
>
>       /*
>        * If there's no dst alpha channel, adjust the blend op so that we'll treat
> diff --git a/src/gallium/state_trackers/xa/xa_renderer.c b/src/gallium/state_trackers/xa/xa_renderer.c
> index fda07e5..bc55f87 100644
> --- a/src/gallium/state_trackers/xa/xa_renderer.c
> +++ b/src/gallium/state_trackers/xa/xa_renderer.c
> @@ -465,9 +465,11 @@ renderer_copy_prepare(struct xa_context *r,
>       }
>
>       /* shaders */
> -    if (src_texture->format == PIPE_FORMAT_L8_UNORM)
> +    if (src_texture->format == PIPE_FORMAT_L8_UNORM ||
> +        src_texture->format == PIPE_FORMAT_R8_UNORM)
>   	fs_traits |= FS_SRC_LUMINANCE;
> -    if (dst_surface->format == PIPE_FORMAT_L8_UNORM)
> +    if (dst_surface->format == PIPE_FORMAT_L8_UNORM ||
> +        dst_surface->format == PIPE_FORMAT_R8_UNORM)
>   	fs_traits |= FS_DST_LUMINANCE;
>       if (xa_format_a(dst_xa_format) != 0 &&
>   	xa_format_a(src_xa_format) == 0)
>

Reviewed-by: Jose Fonseca <jfonseca at vmware.com>