diff --git a/ChangeLog b/ChangeLog
index a90eb2f92a..00cf6f9dd9 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+2007-04-30  Richard Hult  <richard@imendio.com>
+
+	* gdk/quartz/gdkwindow-quartz.c: (gdk_window_set_opacity):
+	Implement.
+
 2007-04-30  Matthias Clasen  <mclasen@redhat.com>
 
 	* modules/printbackends/cups/gtkprintbackendcups.c: Get all
diff --git a/gdk/quartz/gdkwindow-quartz.c b/gdk/quartz/gdkwindow-quartz.c
index 6003064180..07ecd3c1eb 100644
--- a/gdk/quartz/gdkwindow-quartz.c
+++ b/gdk/quartz/gdkwindow-quartz.c
@@ -29,6 +29,9 @@ static gpointer parent_class;
 static GSList *update_windows = NULL;
 static guint update_idle = 0;
 
+#define WINDOW_IS_TOPLEVEL(window)		   \
+  (GDK_WINDOW_TYPE (window) != GDK_WINDOW_CHILD && \
+   GDK_WINDOW_TYPE (window) != GDK_WINDOW_FOREIGN)
 
 NSView *
 gdk_quartz_window_get_nsview (GdkWindow *window)
@@ -2024,3 +2027,24 @@ gdk_window_beep (GdkWindow *window)
 {
   gdk_display_beep (_gdk_display);
 }
+
+void
+gdk_window_set_opacity (GdkWindow *window,
+			gdouble    opacity)
+{
+  GdkWindowObject *private = (GdkWindowObject *) window;
+  GdkWindowImplQuartz *impl = GDK_WINDOW_IMPL_QUARTZ (private->impl);
+
+  g_return_if_fail (GDK_IS_WINDOW (window));
+  g_return_if_fail (WINDOW_IS_TOPLEVEL (window));
+
+  if (GDK_WINDOW_DESTROYED (window))
+    return;
+
+  if (opacity < 0)
+    opacity = 0;
+  else if (opacity > 1)
+    opacity = 1;
+
+  [impl->toplevel setAlphaValue: opacity];
+}