How to send a 'resize' event?

[Jérôme COUDERC <j couderc ifrance com>]

        In my application, some buttons (into a vbox) can be hidden.
My problem is to force GTK to replace the other buttons (which are 
shown) automatically.
I know that the event 'configure' asks to gtk to resize the window, but
I don't know how to use it...

Someone can help me?
regards,
Jerome