[PATCH xserver 3/3] squash: glamor: Fix Render blending for alpha-to-red.

[Eric Anholt]

Signed-off-by: Eric Anholt <eric at anholt.net>
---
 glamor/glamor_render.c | 36 ++++++++++++++++++++++++++++++++----
 1 file changed, 32 insertions(+), 4 deletions(-)

diff --git a/glamor/glamor_render.c b/glamor/glamor_render.c
index c36b345..51718d1 100644
--- a/glamor/glamor_render.c
+++ b/glamor/glamor_render.c
@@ -215,8 +215,8 @@ glamor_create_composite_fs(struct shader_key *key)
         "out vec4 color1;\n"
         "void main()\n"
         "{\n"
-        "	color0 = get_source() * get_mask();\n"
-        "	color1 = get_source().a * get_mask();\n"
+        "	color0 = dest_swizzle(get_source() * get_mask());\n"
+        "	color1 = dest_swizzle(get_source().a * get_mask());\n"
         "}\n";
     const char *header_ca_dual_blend =
         "#version 130\n";
@@ -422,11 +422,29 @@ glamor_lookup_composite_shader(ScreenPtr screen, struct
     return shader;
 }
 
+static GLenum
+glamor_translate_blend_alpha_to_red(GLenum blend)
+{
+    switch (blend) {
+    case GL_SRC_ALPHA:
+        return GL_SRC_COLOR;
+    case GL_DST_ALPHA:
+        return GL_DST_COLOR;
+    case GL_ONE_MINUS_SRC_ALPHA:
+        return GL_ONE_MINUS_SRC_COLOR;
+    case GL_ONE_MINUS_DST_ALPHA:
+        return GL_ONE_MINUS_DST_COLOR;
+    default:
+        return blend;
+    }
+}
+
 static Bool
 glamor_set_composite_op(ScreenPtr screen,
                         CARD8 op, struct blendinfo *op_info_result,
                         PicturePtr dest, PicturePtr mask,
-                        enum ca_state ca_state)
+                        enum ca_state ca_state,
+                        struct shader_key *key)
 {
     GLenum source_blend, dest_blend;
     struct blendinfo *op_info;
@@ -473,6 +491,14 @@ glamor_set_composite_op(ScreenPtr screen,
         }
     }
 
+    /* If we're outputting our alpha to the red channel, then any
+     * reads of alpha for blending need to come from the red channel.
+     */
+    if (key->dest_swizzle == SHADER_DEST_SWIZZLE_ALPHA_TO_RED) {
+        source_blend = glamor_translate_blend_alpha_to_red(source_blend);
+        dest_blend = glamor_translate_blend_alpha_to_red(dest_blend);
+    }
+
     op_info_result->source_blend = source_blend;
     op_info_result->dest_blend = dest_blend;
     op_info_result->source_alpha = op_info->source_alpha;
@@ -1006,8 +1032,10 @@ glamor_composite_choose_shader(CARD8 op,
         goto fail;
     }
 
-    if (!glamor_set_composite_op(screen, op, op_info, dest, mask, ca_state))
+    if (!glamor_set_composite_op(screen, op, op_info, dest, mask, ca_state,
+                                 &key)) {
         goto fail;
+    }
 
     *shader = glamor_lookup_composite_shader(screen, &key);
     if ((*shader)->prog == 0) {
-- 
2.6.4