The map_event signal will be emitted when the
widget's window is mapped.
A window is mapped when it becomes visible on the screen.
To receive this signal, the Window associated to the widget needs to enable the STRUCTURE_MASK mask. GDK will enable this mask automatically for all new windows.
the EventAny which triggered this signal.
true to stop other handlers from being invoked for the event. false to propagate the event further.