parent_relative questions

[Brett Granger <bdgranger alum mit edu>]

I've been experimenting with gdk_window_set_back_pixmap and the 
parent_relative flag under X.  According to the X docs, setting a bg 
pixmap of ParentRelative should indicate that the background of this 
window is the appropriately offset pixmap of whatever's in the bg of the 
parent window.  This seems like it might be yet another way to pretend 
to have transparent top level windows, since the background pixmaps 
should be tiled in such a way as to make the child fit right in over the 
parent.

The first thing I learned is that if I don't 
"gtk_widget_set_app_paintable" I still get the default gray background 
fill.  However, when I set the window to be "app paintable" I would 
expect that I should see the bg pixmap that I have set in my root window 
(since the windows I am playing with are TOPLEVEL).  Instead I get a 
solid black background, regardless of what's in the root window.

Has anybody else had any success with parent_relative windows and can 
anyone comment on whether I really can achieve a fake transparency with 
toplevel windows in this way?  I'm using GTK2.0.

Thanks in advance!
--Brett

ps. directfb is not an option for us, which is why I thought I'd try it 
this way...