`GtkWidgetPaintable` is a `GdkPaintable` that displays the contents of a widget.
`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 [[email protected]:
GtkWidgetPaintable:invalidate-size] signal whenever the size of the widget changes as well as for visual changes by emitting the
[[email protected]:GtkWidgetPaintable:invalidate-contentss] signal whenever the widget changes.
You can use a `GtkWidgetPaintable` everywhere a `GdkPaintable` is allowed, including using it on a `GtkPicture` (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 that the [[email protected]:can-shrink] property is set to
true or you might end up with an infinitely growing widget.