[Gtk-sharp-list] Checking if a window is visible on the screen

[David Ssali]

Greetings,
I am creating an application that needs to display a notification if the 
window is not visible on the screen. By visible i mean minimized or 
fully obstracted by another window.
I have tried the Visibility Notify Event but it does not work when i tab 
away from the window.
How can i do this using Gtk?

Many thanks
David