How to do a graphic overlay?

["Till Harbaum / Lists" <lists harbaum org>]

Hi,

i'd like to do some graphic overlay. In this particular case i'd like to put two buttons on top of a 
goocanvas.

I tried to hook into the expose event and just draw something to the gdkwindow of the widget. That simply 
doesn't work. It works with a gtkdrawingarea, but not with the goocanvas.

What can prevent me from drawing to the gdkwindow of a widget? I also tried to use a seperate window, but 
that's pretty difficult to handle since you e.g. have to move those windows when you move the main window etc 
etc. So just painting their seems simpler ... but unfortunately doesn't work ....

Till