How big is that canvas in the window?

[Bob Greschke]

Here's the idea:

www.passcal.nmt.edu/~bob/unlinked/images/trdpy.jpg

It's in Python/Tkinter.  See the "Plot" button?  I want to draw a
graph in the black area.  How do I find out the dimensions of the
black canvas area???  I can make a guess when I first draw everything
by setting the size of everything, but I don't want to do that.  I
want the user to be able to resize the window and then redraw the
graph.  I got to exactly this same point in GTK+ and had to give up.
Am I going to have to write this program in Java?? :-)

(The program is actually being written for/on a UNIX box.  I just had
to use a Windows machine to get the screen dump.)

Thanks!

Bob