This can be handy when you want to change the sense of a toggle
in the UI without rewriting the underlying logic. Currently, this
is just exposed as a construct-only property. We may add a
convenience wrapper or a special !property syntax for this later.
https://bugzilla.gnome.org/show_bug.cgi?id=728489
Add a new type of GAction that represents the value of a property on an
object. As an example, this might be used on the "visible-child-name"
property of a GtkStack.
https://bugzilla.gnome.org/show_bug.cgi?id=703270