This signal is emitted when a widget is supposed to render itself.
Signal handlers connected to this signal can modify the cairo context passed as
cr in any way they like and don't need to restore
it. The signal emission takes care of calling save before and
restore after invoking the handler.
The signal handler will get a
cr with a clip region already set to the widget's dirty region, i.e. to the area that needs
repainting. Complicated widgets that want to avoid redrawing themselves completely can get the full extents of the clip region with
cairo_get_clip_rectangle, or they can get a finer-grained representation
of the dirty region with copy_clip_rectangle_list.
the cairo context to draw to
true to stop other handlers from being invoked for the event. false to propagate the event further.