Very rarely-used function. This function is used to emit an expose event on a widget. This function is not normally used directly. The only time it is used is when propagating an expose event to a windowless child widget (Widget.getHasWindow is FALSE), and that is normally done using Container.propagateDraw.
If you want to force an area of a window to be redrawn, use Window.invalidateRect or Window.invalidateRegion. To cause the redraw to be done immediately, follow that call with a call to Window.processUpdates.
return from the event signal emission (TRUE if the event was handled)