Post-Resize Callbacks?

[Kyle B Ferrio <kyle U Arizona EDU>]

I have a widget that needs to know whenever it has been resized, so that
it can decide how much and/or what kind of info to display, based on the
new geometry, and then queue a redraw request.  What's the best way to
catch a resize _after_ it happens?  I'm just learning GTK+, so this might
be obvious. 

Thanks,
Kyle