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.
Since 2.4
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. Since 2.4