Attaches the menu to the widget and provides a callback function
that will be invoked when the menu calls gtk_menu_detach() during
its destruction.
If the menu is attached to the widget then it will be destroyed
when the widget is destroyed, as if it was a child widget.
An attached menu will also move between screens correctly if the
widgets moves between screens.
Attaches the menu to the widget and provides a callback function that will be invoked when the menu calls gtk_menu_detach() during its destruction.
If the menu is attached to the widget then it will be destroyed when the widget is destroyed, as if it was a child widget. An attached menu will also move between screens correctly if the widgets moves between screens.