8.4 The CAPI menu hierarchy

The combination of menu items, menu components and menus can create a hierarchical structure as shown schematically in A schematic example of a menu hierarchy and graphically in An example of a menu hierarchy. This menu has five elements, one of which is itself a menu (with three menu items) and the remainder are menu components and menu items. Items in a menu inherit values from their parent, allowing similar elements to share relevant properties whenever possible.

(defun menu-item-name (data)

  (format nil "Menu Item ~D" data))

(defun submenu-item-name (data)

  (format nil "Submenu Item ~D" data))

(contain 

 (make-instance

  'menu 

  :items 

  (list

   (make-instance 'menu-component

                  :items '(1 2)

                  :print-function 'menu-item-name

                  )

   (make-instance 'menu-component

                  :items 

                  (list 3 

                        (make-instance 

                         'menu

                         :title "Submenu"

                         :items '(1 2 3)

                         :print-function

                         'submenu-item-name))

                  :print-function 'menu-item-name)

   (make-instance 'menu-item

                  :data 42))

  :print-function 'menu-item-name))

Figure 8.5 A schematic example of a menu hierarchy

Figure 8.6 An example of a menu hierarchy