[mutter] window: Fix titlebar_is_onscreen() test

[Florian Müllner <fmuellner src gnome org>]

commit 73ca0efaebff3f2f8a840c6aae4bf23e1fc2f577
Author: Florian Müllner <fmuellner gnome org>
Date:   Thu Sep 18 16:29:50 2014 +0100

    window: Fix titlebar_is_onscreen() test
    
    The titlebar rect is in window coordinates, while screen regions are
    obviously not. Fix by translating into screen coordinates before
    testing for overlaps.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=736915

 src/core/window.c |    7 ++++++-
 1 files changed, 6 insertions(+), 1 deletions(-)
---
diff --git a/src/core/window.c b/src/core/window.c
index 404d05a..5c9ecfd 100644
--- a/src/core/window.c
+++ b/src/core/window.c
@@ -5385,7 +5385,7 @@ meta_window_shove_titlebar_onscreen (MetaWindow *window)
 gboolean
 meta_window_titlebar_is_onscreen (MetaWindow *window)
 {
-  MetaRectangle  titlebar_rect;
+  MetaRectangle  titlebar_rect, frame_rect;
   GList         *onscreen_region;
   gboolean       is_onscreen;
 
@@ -5400,6 +5400,11 @@ meta_window_titlebar_is_onscreen (MetaWindow *window)
   /* Get the rectangle corresponding to the titlebar */
   meta_window_get_titlebar_rect (window, &titlebar_rect);
 
+  /* Translate into screen coordinates */
+  meta_window_get_frame_rect (window, &frame_rect);
+  titlebar_rect.x = frame_rect.x;
+  titlebar_rect.y = frame_rect.y;
+
   /* Run through the spanning rectangles for the screen and see if one of
    * them overlaps with the titlebar sufficiently to consider it onscreen.
    */