[GtkGLExt] Using GDK Drawing functions to draw onto a double-buffered widget?

[Fish-face <thefishface gmail com>]

Well, basically, is this possible?

I have the drawable got by gtk_widget_get_gl_drawable() but it appears 
that's the front buffer, so anything I draw directly to it flickers 
horribly.
This is repeated if I use my gdk_draw*() functions after calling 
gdk_gl_drawable_swap_buffers().

I assume there's some way of getting the backbuffer for the widget in 
question, but I haven't found it, yet. Any help would be useful!

Thanks!
--
Chris/Fish-Face