[gtk+] Add documentation note for GtkOffscreenWindow emission of damage-event.

[Cody Russell <bratsche src gnome org>]

commit 09b25f9739b705c786878c05caee3a8c5c2ac9d3
Author: Cody Russell <crussell canonical com>
Date:   Sat Dec 19 16:09:54 2009 +0100

    Add documentation note for GtkOffscreenWindow emission of damage-event.

 gtk/gtkoffscreenwindow.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)
---
diff --git a/gtk/gtkoffscreenwindow.c b/gtk/gtkoffscreenwindow.c
index dd14159..fb6b9d9 100644
--- a/gtk/gtkoffscreenwindow.c
+++ b/gtk/gtkoffscreenwindow.c
@@ -43,6 +43,9 @@
  * detail.  Applications should not use any API specific to #GtkWindow
  * to operate on this object.  It should be treated as a #GtkBin that
  * has no parent widget.
+ *
+ * When contained offscreen widgets are redrawn, #GtkOffscreenWindow
+ * will emit a "damage-event" signal.
  */
 
 G_DEFINE_TYPE (GtkOffscreenWindow, gtk_offscreen_window, GTK_TYPE_WINDOW);