[mutter] Adapt to premultiplied alpha usage in Cogl

[Owen Taylor <otaylor src gnome org>]

commit 442991a712e6dc34ebf890aaa5f1343666c96d56
Author: Owen W. Taylor <otaylor fishsoup net>
Date:   Thu Jun 11 15:33:05 2009 -0400

    Adapt to premultiplied alpha usage in Cogl
    
    Cogl's default blend function has been switched to expect premultiplied
    alpha. Change the combine function and the colors we use to
    modulate alpha to match.
    
    http://bugzilla.gnome.org/show_bug.cgi?id=585480

 src/compositor/mutter/mutter-shaped-texture.c   |   14 ++++++++------
 src/compositor/mutter/tidy/tidy-texture-frame.c |    2 +-
 2 files changed, 9 insertions(+), 7 deletions(-)
---
diff --git a/src/compositor/mutter/mutter-shaped-texture.c b/src/compositor/mutter/mutter-shaped-texture.c
index ef78e25..9a91150 100755
--- a/src/compositor/mutter/mutter-shaped-texture.c
+++ b/src/compositor/mutter/mutter-shaped-texture.c
@@ -283,8 +283,7 @@ mutter_shaped_texture_paint (ClutterActor *actor)
       priv->material = cogl_material_new ();
 
       cogl_material_set_layer_combine (priv->material, 1,
-				       "RGB = REPLACE (PREVIOUS)"
-				       "A = MODULATE (PREVIOUS, TEXTURE)",
+				       "RGBA = MODULATE (PREVIOUS, TEXTURE[A])",
 				       NULL);
     }
   material = priv->material;
@@ -305,9 +304,12 @@ mutter_shaped_texture_paint (ClutterActor *actor)
         {
           material = priv->material_workaround = cogl_material_new ();
 
+	  cogl_material_set_layer_combine (material, 0,
+					   "RGB = MODULATE (TEXTURE, PREVIOUS)"
+					   "A = REPLACE (PREVIOUS)",
+					   NULL);
 	  cogl_material_set_layer_combine (material, 1,
-					   "RGB = REPLACE (PREVIOUS)"
-					   "A = MODULATE (PRIMARY, TEXTURE)",
+					   "RGBA = MODULATE (PREVIOUS, TEXTURE[A])",
 					   NULL);
         }
 
@@ -320,8 +322,8 @@ mutter_shaped_texture_paint (ClutterActor *actor)
 
   {
     CoglColor color;
-    cogl_color_set_from_4ub (&color, 255, 255, 255,
-                             clutter_actor_get_paint_opacity (actor));
+    guchar opacity = clutter_actor_get_paint_opacity (actor);
+    cogl_color_set_from_4ub (&color, opacity, opacity, opacity, opacity);
     cogl_material_set_color (material, &color);
   }
 
diff --git a/src/compositor/mutter/tidy/tidy-texture-frame.c b/src/compositor/mutter/tidy/tidy-texture-frame.c
index 28ca96a..879cb61 100644
--- a/src/compositor/mutter/tidy/tidy-texture-frame.c
+++ b/src/compositor/mutter/tidy/tidy-texture-frame.c
@@ -210,7 +210,7 @@ tidy_texture_frame_paint (ClutterActor *self)
   g_assert (priv->material != COGL_INVALID_HANDLE);
 
   /* set the source material using the parent texture's COGL handle */
-  cogl_material_set_color4ub (priv->material, 255, 255, 255, opacity);
+  cogl_material_set_color4ub (priv->material, opacity, opacity, opacity, opacity);
   cogl_material_set_layer (priv->material, 0, cogl_texture);
   cogl_set_source (priv->material);