gdk: Track the layered area

We track the areas that have alpha coverage so that we can
avoid using these as sources when copying window contents.
We also don't remove such areas from the clipping regions so
that they are painted both by parent and child.

diff --git a/gdk/gdkinternals.h b/gdk/gdkinternals.h
index 9bd1ea9e651d501f5cbbcd65732a17ad23a6e4e3..8567fd4fb3c5a3701c1e17bdbec03f075b699af8 100644 (file)
--- a/gdk/gdkinternals.h
+++ b/gdk/gdkinternals.h
@@ -229,8 +229,17 @@ struct _GdkWindow
   gint abs_x, abs_y; /* Absolute offset in impl */
   gint width, height;
 
-  cairo_region_t *clip_region; /* Clip region (wrt toplevel) in window coords */
-  cairo_region_t *clip_region_with_children; /* Clip region in window coords */
+  /* The clip region is the part of the window, in window coordinates
+     that is fully or partially (i.e. semi transparently) visible in
+     the window hierarchy from the toplevel and down */
+  cairo_region_t *clip_region;
+  /* This is the clip region, with additionally all the opaque
+     child windows removed */
+  cairo_region_t *clip_region_with_children;
+  /* The layered region is the subset of clip_region that
+     is covered by non-opaque sibling or ancestor sibling window. */
+  cairo_region_t *layered_region;
+
   GdkCursor *cursor;
   GHashTable *device_cursor;
 

diff --git a/gdk/gdkwindow.c b/gdk/gdkwindow.c
index ae0850c58bfd21f4d93be159d1c307acffd14a8a..d1ac763efa2b720bebe796a7c745e86f10b910b3 100644 (file)
--- a/gdk/gdkwindow.c
+++ b/gdk/gdkwindow.c
@@ -652,7 +652,8 @@ static void
 remove_child_area (GdkWindow *private,
                   GdkWindow *until,
                   gboolean for_input,
-                  cairo_region_t *region)
+                  cairo_region_t *region,
+                  cairo_region_t *layered_region)
 {
   GdkWindow *child;
   cairo_region_t *child_region;
@@ -723,7 +724,13 @@ remove_child_area (GdkWindow *private,
            }
        }
 
-      cairo_region_subtract (region, child_region);
+      if (child->has_alpha_background)
+       {
+         if (layered_region != NULL)
+           cairo_region_union (layered_region, child_region);
+       }
+      else
+       cairo_region_subtract (region, child_region);
       cairo_region_destroy (child_region);
 
     }
@@ -868,7 +875,7 @@ recompute_visible_regions_internal (GdkWindow *private,
   GdkRectangle r;
   GList *l;
   GdkWindow *child;
-  cairo_region_t *new_clip, *old_clip_region_with_children;
+  cairo_region_t *new_clip, *new_layered;
   gboolean clip_region_changed;
   gboolean abs_pos_changed;
   int old_abs_x, old_abs_y;
@@ -901,6 +908,7 @@ recompute_visible_regions_internal (GdkWindow *private,
   clip_region_changed = FALSE;
   if (recalculate_clip)
     {
+      new_layered = cairo_region_create ();
       if (private->viewable)
        {
          /* Calculate visible region (sans children) in parent window coords */
@@ -913,35 +921,45 @@ recompute_visible_regions_internal (GdkWindow *private,
          if (!gdk_window_is_toplevel (private))
            {
              cairo_region_intersect (new_clip, private->parent->clip_region);
+             cairo_region_union (new_layered, private->parent->layered_region);
 
              /* Remove all overlapping children from parent. */
-             remove_child_area (private->parent, private, FALSE, new_clip);
+             remove_child_area (private->parent, private, FALSE, new_clip, new_layered);
            }
 
          /* Convert from parent coords to window coords */
          cairo_region_translate (new_clip, -private->x, -private->y);
+         cairo_region_translate (new_layered, -private->x, -private->y);
 
          if (private->shape)
            cairo_region_intersect (new_clip, private->shape);
        }
       else
-       new_clip = cairo_region_create ();
+         new_clip = cairo_region_create ();
 
+      cairo_region_intersect (new_layered, new_clip);
+      
       if (private->clip_region == NULL ||
          !cairo_region_equal (private->clip_region, new_clip))
        clip_region_changed = TRUE;
 
+      if (private->layered_region == NULL ||
+         !cairo_region_equal (private->layered_region, new_layered))
+       clip_region_changed = TRUE;
+      
       if (private->clip_region)
        cairo_region_destroy (private->clip_region);
       private->clip_region = new_clip;
 
-      old_clip_region_with_children = private->clip_region_with_children;
+      if (private->layered_region != NULL)
+       cairo_region_destroy (private->layered_region);
+      private->layered_region = new_layered;
+
+      if (private->clip_region_with_children)
+       cairo_region_destroy (private->clip_region_with_children);
       private->clip_region_with_children = cairo_region_copy (private->clip_region);
       if (private->window_type != GDK_WINDOW_ROOT)
-       remove_child_area (private, NULL, FALSE, private->clip_region_with_children);
-
-      if (old_clip_region_with_children)
-       cairo_region_destroy (old_clip_region_with_children);
+       remove_child_area (private, NULL, FALSE, private->clip_region_with_children, NULL);
     }
 
   if (clip_region_changed)
@@ -7163,7 +7181,7 @@ do_child_shapes (GdkWindow *window,
   r.height = window->height;
 
   region = cairo_region_create_rectangle (&r);
-  remove_child_area (window, NULL, FALSE, region);
+  remove_child_area (window, NULL, FALSE, region, NULL);
 
   if (merge && window->shape)
     cairo_region_subtract (region, window->shape);
@@ -7282,7 +7300,7 @@ do_child_input_shapes (GdkWindow *window,
   r.height = window->height;
 
   region = cairo_region_create_rectangle (&r);
-  remove_child_area (window, NULL, TRUE, region);
+  remove_child_area (window, NULL, TRUE, region, NULL);
 
   if (merge && window->shape)
     cairo_region_subtract (region, window->shape);