[gnome-shell] [StThemeNode] Make shadows respect paint opacity

[Florian Müllner <fmuellner src gnome org>]

commit a433a1c637d856d2be86b88f0c03e943fdaa0da9
Author: Florian Müllner <fmuellner src gnome org>
Date:   Wed May 19 15:09:19 2010 +0200

    [StThemeNode] Make shadows respect paint opacity
    
    Currently shadows disregard the overall opacity, so e.g. setting
    an ancestor's opacity does not effect the shadow. Fix this by
    deferring the setting of the shadow's color until it is painted.
    Also move duplicated drawing code from st_theme_node_paint() into
    its own function.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=619083

 src/st/st-theme-node-drawing.c |  100 +++++++++++++++++----------------------
 1 files changed, 44 insertions(+), 56 deletions(-)
---
diff --git a/src/st/st-theme-node-drawing.c b/src/st/st-theme-node-drawing.c
index ec226de..1295497 100644
--- a/src/st/st-theme-node-drawing.c
+++ b/src/st/st-theme-node-drawing.c
@@ -76,7 +76,6 @@ static CoglHandle
 create_shadow_material (StThemeNode  *node,
                         CoglHandle    src_texture)
 {
-  CoglColor   color;
   CoglHandle  material;
   CoglHandle  texture;
   StShadow   *shadow_spec;
@@ -199,19 +198,11 @@ create_shadow_material (StThemeNode  *node,
 
   material = cogl_material_new ();
 
-  cogl_color_set_from_4ub (&color,
-                           shadow_spec->color.red, shadow_spec->color.green,
-                           shadow_spec->color.blue, shadow_spec->color.alpha);
-  cogl_color_premultiply (&color);
-
-  cogl_material_set_layer_combine_constant (material, 0, &color);
   cogl_material_set_layer (material, 0, texture);
 
-  /* We ignore the material color, which encodes the overall opacity of the
-   * actor, so setting an ancestor of the shadow to partially opaque won't
-   * work. The easiest way to fix this would be to not set the combine or constant color
-   * here, then in paint set the material color to the shadow_spec_color *
-   * paint_opacity.*/
+  /* We set up the material to blend the shadow texture with the combine
+   * constant, but defer setting the latter until painting, so that we can
+   * take the actor's overall opacity into account. */
   cogl_material_set_layer_combine (material, 0,
                                    "RGBA = MODULATE (CONSTANT, TEXTURE[A])",
                                    NULL);
@@ -823,6 +814,39 @@ paint_texture_with_opacity (CoglHandle       texture,
 }
 
 static void
+paint_shadow_with_opacity (CoglHandle       shadow_material,
+                           StShadow        *shadow_spec,
+                           ClutterActorBox *box,
+                           guint8           paint_opacity)
+{
+  ClutterActorBox shadow_box;
+  CoglColor       color;
+
+  shadow_box.x1 = box->x1 + shadow_spec->xoffset
+                  - shadow_spec->blur - shadow_spec->spread;
+  shadow_box.y1 = box->y1 + shadow_spec->yoffset
+                  - shadow_spec->blur - shadow_spec->spread;
+  shadow_box.x2 = box->x2 + shadow_spec->xoffset
+                  + shadow_spec->blur + shadow_spec->spread;
+  shadow_box.y2 = box->y2 + shadow_spec->yoffset
+                  + shadow_spec->blur + shadow_spec->spread;
+
+  cogl_color_set_from_4ub (&color,
+                           shadow_spec->color.red   * paint_opacity / 255,
+                           shadow_spec->color.green * paint_opacity / 255,
+                           shadow_spec->color.blue  * paint_opacity / 255,
+                           shadow_spec->color.alpha * paint_opacity / 255);
+  cogl_color_premultiply (&color);
+
+  cogl_material_set_layer_combine_constant (shadow_material, 0, &color);
+
+  cogl_set_source (shadow_material);
+  cogl_rectangle_with_texture_coords (shadow_box.x1, shadow_box.y1,
+                                      shadow_box.x2, shadow_box.y2,
+                                      0, 0, 1, 1);
+}
+
+static void
 st_theme_node_paint_borders (StThemeNode           *node,
                              const ClutterActorBox *box,
                              guint8                 paint_opacity)
@@ -1087,28 +1111,10 @@ st_theme_node_paint (StThemeNode           *node,
    */
 
   if (node->border_shadow_material)
-    {
-      StShadow *shadow_spec;
-      ClutterActorBox shadow_box;
-
-      shadow_spec = node->shadow;
-
-      shadow_box.x1 = allocation.x1 + shadow_spec->xoffset
-                      - shadow_spec->blur - shadow_spec->spread;
-      shadow_box.y1 = allocation.y1 + shadow_spec->yoffset
-                      - shadow_spec->blur - shadow_spec->spread;
-      shadow_box.x2 = allocation.x2 + shadow_spec->xoffset
-                      + shadow_spec->blur + shadow_spec->spread;
-      shadow_box.y2 = allocation.y2 + shadow_spec->yoffset
-                      + shadow_spec->blur + shadow_spec->spread;
-
-      cogl_material_set_color4ub (node->border_shadow_material,
-                                  paint_opacity, paint_opacity, paint_opacity, paint_opacity);
-
-      cogl_set_source (node->border_shadow_material);
-      cogl_rectangle_with_texture_coords (shadow_box.x1, shadow_box.y1, shadow_box.x2, shadow_box.y2,
-                                          0, 0, 1, 1);
-    }
+    paint_shadow_with_opacity (node->border_shadow_material,
+                               node->shadow,
+                               &allocation,
+                               paint_opacity);
 
   if (node->border_texture != COGL_INVALID_HANDLE)
     {
@@ -1140,28 +1146,10 @@ st_theme_node_paint (StThemeNode           *node,
        * like boder and background color into account).
        */
       if (node->background_shadow_material != COGL_INVALID_HANDLE)
-        {
-          StShadow *shadow_spec;
-          ClutterActorBox shadow_box;
-
-          shadow_spec = node->shadow;
-
-          shadow_box.x1 = background_box.x1 + shadow_spec->xoffset
-                          - shadow_spec->blur - shadow_spec->spread;
-          shadow_box.y1 = background_box.y1 + shadow_spec->yoffset
-                          - shadow_spec->blur - shadow_spec->spread;
-          shadow_box.x2 = background_box.x2 + shadow_spec->xoffset
-                          + shadow_spec->blur + shadow_spec->spread;
-          shadow_box.y2 = background_box.y2 + shadow_spec->yoffset
-                          + shadow_spec->blur + shadow_spec->spread;
-
-          cogl_material_set_color4ub (node->background_shadow_material,
-                                      paint_opacity, paint_opacity, paint_opacity, paint_opacity);
-
-          cogl_set_source (node->background_shadow_material);
-          cogl_rectangle_with_texture_coords (shadow_box.x1, shadow_box.y1, shadow_box.x2, shadow_box.y2,
-                                              0, 0, 1, 1);
-        }
+        paint_shadow_with_opacity (node->background_shadow_material,
+                                   node->shadow,
+                                   &background_box,
+                                   paint_opacity);
 
       paint_texture_with_opacity (node->background_texture, &background_box, paint_opacity);
     }