[gtk+] Describe how gdk_x11_drawable_get_xid() works wrt CSW in docs

[Alexander Larsson <alexl src gnome org>]

commit 36809d400f820bea837f4051ef0918d018b759b7
Author: Alexander Larsson <alexl redhat com>
Date:   Mon Aug 31 16:16:23 2009 +0200

    Describe how gdk_x11_drawable_get_xid() works wrt CSW in docs

 .../reference/gtk/migrating-ClientSideWindows.sgml |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)
---
diff --git a/docs/reference/gtk/migrating-ClientSideWindows.sgml b/docs/reference/gtk/migrating-ClientSideWindows.sgml
index 4880134..96372f7 100644
--- a/docs/reference/gtk/migrating-ClientSideWindows.sgml
+++ b/docs/reference/gtk/migrating-ClientSideWindows.sgml
@@ -13,6 +13,9 @@
     longer correct to assume that each window has an associated XID.
     Code that makes this assumption can sometimes be fixed by calling
     gdk_window_ensure_native() on the windows in question.
+    Calling gdk_x11_drawable_get_xid() from the X11-specific API on a
+    non-native window will explicitly call gdk_window_ensure_native(),
+    so old code using this will continue to work.
   </para>
 
   <para>