[Intel-gfx] [PATCH] i915: Do not force the incoming source alpha to 1.

[Clemens Eisserer]

This really made my day :)
Thank you very very much for  fixing this :D

- Clemens

2009/11/10 Chris Wilson <chris at chris-wilson.co.uk>:
> RENDER specifies that textures are extended with the clear colour in the
> EXTEND_NONE case. By forcing the border colour to contain 1, we were
> padding with black instead. This is a long standing bug that causes
> numerous failure in cairo and has been frequently bemoaned about in
> bugzilla.
>
>  https://bugs.freedesktop.org/show_bug.cgi?id=17933
>  x8r8g8b8 doesn't sample alpha=0 outside surface bounds
>
> However, one consequence of this is that we now must trust the incoming
> source alpha for x8r8g8b8 surfaces (and similar ignored alpha formats).
> We workaround this by ensuring that we fill the outgoing alpha channel
> with 1 for such targets, but we must also rely on the X server to fill
> the alpha channel on incoming RGB images.
>
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> ---
>  src/i915_render.c |    9 +++------
>  1 files changed, 3 insertions(+), 6 deletions(-)
>
> diff --git a/src/i915_render.c b/src/i915_render.c
> index f64e031..8d8fde4 100644
> --- a/src/i915_render.c
> +++ b/src/i915_render.c
> @@ -446,7 +446,6 @@ static void i915_emit_composite_setup(ScrnInfoPtr scrn)
>  {
>        intel_screen_private *intel = intel_get_screen_private(scrn);
>        int op = intel->i915_render_state.op;
> -       PicturePtr source_picture = intel->render_source_picture;
>        PicturePtr mask_picture = intel->render_mask_picture;
>        PicturePtr dest_picture = intel->render_dest_picture;
>        PixmapPtr mask = intel->render_mask;
> @@ -600,10 +599,6 @@ static void i915_emit_composite_setup(ScrnInfoPtr scrn)
>                    i915_fs_texldp(FS_R0, FS_S0, FS_T0);
>                }
>
> -               /* If the texture lacks an alpha channel, force the alpha to 1. */
> -               if (PICT_FORMAT_A(source_picture->format) == 0)
> -                   i915_fs_mov_masked(FS_R0, MASK_W, i915_fs_operand_one());
> -
>                src_reg = FS_R0;
>            }
>
> @@ -653,7 +648,9 @@ static void i915_emit_composite_setup(ScrnInfoPtr scrn)
>                }
>            }
>            if (dst_format == COLR_BUF_8BIT)
> -               i915_fs_mov(FS_OC, i915_fs_operand(out_reg, W, W, W, W));
> +                   i915_fs_mov(FS_OC, i915_fs_operand(out_reg, W, W, W, W));
> +           if (PICT_FORMAT_A(dest_picture->format) == 0)
> +                   i915_fs_mov_masked(FS_OC, MASK_W, i915_fs_operand_one());
>
>            FS_END();
>        }
> --
> 1.6.5.2
>
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