public class WidgetPaintable : Object, Paintable
GtkWidgetPaintable will also take care of the widget not being in a state where it can be drawn (like when it isn't shown) and just draw nothing or where it does not have a size (like when it is hidden) and report no size in that case.
Of course, GtkWidgetPaintable allows you to monitor widgets for size changes by emitting the invalidate_size signal whenever the size of the widget changes as well as for visual changes by emitting the invalidate_contents signal whenever the widget changes.
You can of course use a GtkWidgetPaintable everywhere a Paintable is allowed, including using it on a Picture (or one of its parents) that it was set on itself via set_paintable. The paintable will take care of recursion when this happens. If you do this however, ensure the can_shrink property is set to true or you might end up with an infinitely growing widget.