public static interface Widget.MapEvent
This can be used as an indication that your Window is no longer
minimized. Connecting to
Widget.Draw would probably tell you
what you need to know, but if all you want to do is find out your app
is [back] onscreen then
Widget.Draw would be a bit heavy
handed. Of course, if you are drawing anyway, then it's fine. See
Widget.UnmapEvent for examples of other variations on the theme
of tracking the state of your application.
The interaction between the GTK library we use, its underlying GDK resource management layer, and the the X windowing system which GDK wraps, is complex. Sometimes there is more than one way to do things.