The ::grab-notify signal is emitted when a widget becomes
shadowed by a GTK+ grab (not a pointer or keyboard grab) on
another widget, or when it becomes unshadowed due to a grab
being removed.
A widget is shadowed by a gtk_grab_add() when the topmost
grab widget in the grab stack of its window group is not
its ancestor.
The ::grab-notify signal is emitted when a widget becomes shadowed by a GTK+ grab (not a pointer or keyboard grab) on another widget, or when it becomes unshadowed due to a grab being removed.
A widget is shadowed by a gtk_grab_add() when the topmost grab widget in the grab stack of its window group is not its ancestor.