If @menu_item_id matches the string passed to
gtk_tool_item_set_proxy_menu_item() return the corresponding #GtkMenuItem.
Custom subclasses of #GtkToolItem should use this function to
update their menu item when the #GtkToolItem changes. That the
@menu_item_ids must match ensures that a #GtkToolItem
will not inadvertently change a menu item that they did not create.
If @menu_item_id matches the string passed to gtk_tool_item_set_proxy_menu_item() return the corresponding #GtkMenuItem.
Custom subclasses of #GtkToolItem should use this function to update their menu item when the #GtkToolItem changes. That the @menu_item_ids must match ensures that a #GtkToolItem will not inadvertently change a menu item that they did not create.