How can I make transparent canvases?

[Henning Kulander <hennikul ifi uio no>]

Hi!

I'm making a UPS monitor for Gnome as a way of learning Gnome
programming.
In this program I'm using several canvases with non-square widgets in
them. It looks kindof strange if you have a pixmap-theme in GTK, because
the pixmap won't shine through the canvas, it will only display a
similar color.

See this screenshot: http://www.exploits.org/nut/library/gupsc.html for
an example of how this program looks with a pixmap theme.

If I have understood correctly the trick is to get a pixbuf or something
of the underlying background and display this in my canvas. How can this
be accomplished? How do I make this pixbuf before creating the canvas,
and how do I grab the underlying background?


Regards!
Henning Kulander