What event has happened?

["hzeng" <hzeng hf tvia com>]

Hi,
    At the virtual screen of XWindow,when I do nothing to my app window and only move the
 mouse, so my app window will move out of the view port bordered by the monitor. In this
 situation I want to do some thing in my app, but how can I get the signal, or what event
 happen? 

Thank you very much !
Hzeng