A checkable-menu-item% is a string-labelled menu item that maintains a checkmark. Its parent must be a menu% or popup-menu%. When the user selects the menu item, the item's checkmark is toggled and its callback procedure is called.
Creates a new menu item in parent. The item is initially shown, appended to the end of its parent, and unchecked. The callback procedure is called (with the event type 'menu) when the menu item is selected (either via a menu bar or popup-menu in canvas<%>).
See set-label for information about mnemonic ampersands (``&'') in label.
If shortcut is not #f, the item has a shortcut. See get-shortcut for more information.
If help is not #f, the item has a help string. See get-help-string for more information.