[gnome-shell] StThemeNodeTransition: work around Cogl bug

[Owen Taylor <otaylor src gnome org>]

commit 8f0f159960d1db92af35ebc6c144b3d1844f43b6
Author: Owen W. Taylor <otaylor fishsoup net>
Date:   Thu Sep 23 10:04:44 2010 -0400

    StThemeNodeTransition: work around Cogl bug
    
    Switch to using the layer combine constant rather than the material
    primary color for representing the opacity of the material; this
    avoids triggering a Cogl bug where changing the primary color corrupts
    the layer state.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=629616

 src/st/st-theme-node-transition.c |    9 +++++----
 1 files changed, 5 insertions(+), 4 deletions(-)
---
diff --git a/src/st/st-theme-node-transition.c b/src/st/st-theme-node-transition.c
index 319cea7..3a3eaf2 100644
--- a/src/st/st-theme-node-transition.c
+++ b/src/st/st-theme-node-transition.c
@@ -263,7 +263,7 @@ setup_framebuffers (StThemeNodeTransition *transition,
                                            NULL);
           cogl_material_set_layer_combine (material_template, 2,
                                            "RGBA = MODULATE (PREVIOUS, "
-                                                            "PRIMARY)",
+                                                            "CONSTANT)",
                                            NULL);
         }
       priv->material = cogl_material_copy (material_template);
@@ -322,9 +322,10 @@ st_theme_node_transition_paint (StThemeNodeTransition *transition,
                           clutter_alpha_get_alpha (priv->alpha));
   cogl_material_set_layer_combine_constant (priv->material, 1, &constant);
 
-  cogl_material_set_color4ub (priv->material,
-                              paint_opacity, paint_opacity,
-                              paint_opacity, paint_opacity);
+  cogl_color_set_from_4ub (&constant,
+                           paint_opacity, paint_opacity,
+                           paint_opacity, paint_opacity);
+  cogl_material_set_layer_combine_constant (priv->material, 2, &constant);
 
   cogl_set_source (priv->material);
   cogl_rectangle_with_multitexture_coords (priv->offscreen_box.x1,