How to set up a response when the user resizes window

[Dwayne Carter <dwaynec clear net nz>]

Hi there, 
	I am working on a drawing application and I would like to be able to
update some program state variables when the user resizes the window. Is
there a signal emitted when the user resizes then window? How do I hook
up to it? Is there a function equivalent to on_user_resize() ?? I've
tried on_check_resize() but this seems to have catastrophic side
effects.

Any help is appreciated
Cheers
Dwayne