gdkwindow: Apply layered areas to the shape for native windows

If a window is overlapped by a layered (i.e. partially transparent)
window then that region will not disappear from the native window clip
region. This lets us handle compositing multiple layers of windows.

For native subwindows this doesn't really work. For them we apply the
clip region as a shape to the native window which lets us have client
side windows overlapping the native window. However, with the addition
of the layered stuff the "overlapped-by-alpha-csw" part got broken, as
this area is not removed from the clip region of the native window.

We fix this by also removing the layered area when applying the shape.
This means alpha and alpha backgrounds don't work over native windows,
but there is not much to do about that.

https://bugzilla.gnome.org/show_bug.cgi?id=696370

diff --git a/gdk/gdkwindow.c b/gdk/gdkwindow.c
index 768620060f0731c4bc82fbc2fe6a1624428fc006..f9628f3e8e30ffb81c56251eb0f1d7bc3c0265d5 100644 (file)
--- a/gdk/gdkwindow.c
+++ b/gdk/gdkwindow.c
@@ -940,19 +940,26 @@ static void
 apply_clip_as_shape (GdkWindow *window)
 {
   GdkRectangle r;
+  cairo_region_t *region;
 
   r.x = r.y = 0;
   r.width = window->width;
   r.height = window->height;
 
+  region = cairo_region_copy (window->clip_region);
+  if (window->layered_region)
+    cairo_region_subtract (region, window->layered_region);
+
   /* We only apply the clip region if would differ
      from the actual clip region implied by the size
      of the window. This is to avoid unneccessarily
      adding meaningless shapes to all native subwindows */
-  if (!region_rect_equal (window->clip_region, &r))
-    apply_shape (window, window->clip_region);
+  if (!region_rect_equal (region, &r))
+    apply_shape (window, region);
   else
     apply_shape (window, NULL);
+
+  cairo_region_destroy (region);
 }
 
 static void