This is an event signal, initially emitted when the connected widget
becomes fully visible on screen. Every widget can capture expose
events; they are even synthesized for widgets that don't have
a GdkWindow.
Expose events are also generated when a widget has been partially
or fully covered by another widget, and is re-exposed. These events
trigger a redraw internally; a GdkWindow
that is not currently exposed is not currently drawn, and the same
applies to any unexposed area of a window.
Following suit, the most likely reason to connect to an
"expose-event" signal is
that you have a drawing function in the callback.
See also: "event",
GtkDrawingArea, GdkWindow,
and the numerous GTK and GDK drawing functions filed under 'Misc'.
