figsize has no effect in embedded GTK2

Hello,

I tried to embed matplotlib in a GTK2 application (using pygtk & glade) but encountered a problem.
As I have been playing with it for a while I think that for its demonstration it is enough to look at the matplotlib example:
embedding_in_gtk2.py (from the example directory of matplotlib)

There, for me the figsize line:
fig = Figure(figsize=(6,6), dpi=100)
has no effect whatsoever (when tryong to change the size)…
The window size is simply set with
win.set_default_size(400,300)
and the figure is always of the same size…
Can anybody tell me why?

(In my own application, if I do not explicitely specify a window size, I always get a window that is too small and has to be resized by hand.)

Currently I am using Windows XP with
matplotlib 0.87.4
pygtk 2.8.6

Thank you for any idea!
Ruda