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.