gtk/gtk.go
func (v *MenuButton) SetPopup(menu IMenu) {
	C.gtk_menu_button_set_popup(v.native(), menu.toWidget())
}
func (v *MenuButton) SetPopup(menu IMenu) {
	C.gtk_menu_button_set_popup(v.native(), menu.toWidget())
}
// SetPopup is a wrapper around gtk_menu_button_set_popup().