Getting native X Window from GtkWidget

[Jörg Henne <j henne levigo de>]

Hi all,

I am trying to turn an application window implemented in wxPython into a 
KDE system tray applet. Just to make this clear: I am not talking about 
the taskbar representation of a window, but the area which displays just 
icons, like the "loudspeaker" icon which controls the mixer etc.

The KDE documentation says that any (non-KDE) window can be made a tray 
icon, by setting a property like this:

   Atom statom =
       XInternAtom( d, "_KDE_NET_WM_SYSTEM_TRAY_WINDOW_FOR", False);
   XChangeProperty( d, win, statom, XA_WINDOW, 32,
                   PropModeReplace, NULL, 1);

With d being the display and win the window. Now I am wondering how I 
get this information from a GtkWidget reference. I can ask any GtkWidget 
for its parent GdkWindow window using gtk_widget_get_parent_window. And 
I found this: 
http://developer.gnome.org/doc/API/2.0/gdk/gdk-X-Window-System-Interaction.html
but there doesn't seem to be a method which returns a GdkNativeWindow 
for a given GdkWindow.

Can anybody help with a pointer or a code snippet?

Thanks in advance
Joerg Henne