https://bugs.launchpad.net/moonshot-ui/+bug/1279798
("UI doesn't take focus when already open")
The problem was that simply calling Window.show() doesn't mean that the window
is brought to the foreground. Actually, there is nothing that guarantees this,
because the user's settings and choice of window manager may affect the
behavior. However, research and experimentation shows that calling these
two Gtk.Window methods:
set_urgency_hint(true);
present();
does not bring the window to the foreground either, but does at least cause
the user to be notified that the window wants attention, much like the way
Windows may make a taskbar icon flash orange.