When a Gtk.Container receives an expose event, it must send synthetic expose events to all children that do not have their own Gdk.Windows. This function provides a convenient way of doing this. A Gtk.Container, when it receives an expose event, calls Container.PropagateExpose(Widget, Gdk.EventExpose) once for each child, passing in the event the Gtk.Container received.

Container.PropagateExpose(Widget, Gdk.EventExpose) takes care of deciding whether an expose event needs to be sent to the child, intersecting the event's area with the child area, and sending the event.

In most cases, a Gtk.Container can either simply inherit the expose implementation from Gtk.Container, or do some drawing and then chain to the expose implementation from Gtk.Container.