[gtk+/transparent-windows: 7/8] gdk: Fix repaint of layered region during scroll

[Alexander Larsson <alexl src gnome org>]

commit 8e28f53a1db931b62826f7ce4c47b81cbc4c4c05
Author: Alexander Larsson <alexl redhat com>
Date:   Thu Dec 1 16:45:18 2011 +0100

    gdk: Fix repaint of layered region during scroll

 gdk/gdkwindow.c |   11 +++++++++--
 1 files changed, 9 insertions(+), 2 deletions(-)
---
diff --git a/gdk/gdkwindow.c b/gdk/gdkwindow.c
index 7265f78..c13b9a8 100644
--- a/gdk/gdkwindow.c
+++ b/gdk/gdkwindow.c
@@ -6266,7 +6266,7 @@ gdk_window_scroll (GdkWindow *window,
 		   gint       dy)
 {
   GdkWindow *impl_window;
-  cairo_region_t *copy_area, *noncopy_area;
+  cairo_region_t *copy_area, *noncopy_area, *old_layered_area;
   cairo_region_t *old_native_child_region, *new_native_child_region;
   GList *tmp_list;
 
@@ -6280,6 +6280,7 @@ gdk_window_scroll (GdkWindow *window,
 
   gdk_window_flush_if_exposing (window);
 
+  old_layered_area = cairo_region_copy (window->layered_region);
   old_native_child_region = collect_native_child_region (window, FALSE);
   if (old_native_child_region)
     {
@@ -6320,7 +6321,11 @@ gdk_window_scroll (GdkWindow *window,
   impl_window = gdk_window_get_impl_window (window);
 
   /* Calculate the area that can be gotten by copying the old area */
-  copy_area = cairo_region_copy (window->clip_region);
+  if (window->has_alpha_background)
+    copy_area = cairo_region_create (); /* Copy nothing for alpha windows */
+  else
+    copy_area = cairo_region_copy (window->clip_region);
+  cairo_region_subtract (copy_area, old_layered_area);
   if (old_native_child_region)
     {
       /* Don't copy from inside native children, as this is copied by
@@ -6334,6 +6339,7 @@ gdk_window_scroll (GdkWindow *window,
     }
   cairo_region_translate (copy_area, dx, dy);
   cairo_region_intersect (copy_area, window->clip_region);
+  cairo_region_subtract (copy_area, window->layered_region);
 
   /* And the rest need to be invalidated */
   noncopy_area = cairo_region_copy (window->clip_region);
@@ -6355,6 +6361,7 @@ gdk_window_scroll (GdkWindow *window,
   gdk_window_invalidate_region_full (window, noncopy_area, TRUE, CLEAR_BG_ALL);
 
   cairo_region_destroy (noncopy_area);
+  cairo_region_destroy (old_layered_area);
 
   if (old_native_child_region)
     {