the Fruits menu - a multilevel menu

Similar to the Miles menu, we now consider the implementation of the Fruits menu, which contains multiple levels. It is implemented by the following call :

install_menu('Fruit', 
 	[apple([ 'Granny Smith',	
		 'Delicious'(['Red','Golden']),
		 'Macintosh',
		 'Cox']),
	 pear,
	 orange(['Jaffa',
		 'Seville',
		 'Navel'])]).

• This will install a menu called Fruit on the menu bar - with three items apple, pear, orange
• apple and orange contain submenus, and the Delicious option of apple contains a further submenu
• If the user selects Golden, the goal

  'Delicious'( 'Golden')

  will be called

• If the user selects Seville, then the Prolog goal

  orange( 'Seville')

  will be called

  
Figure 5: The Fruit Menu added to the Menu Bar

  
Figure 8: The Fruit Menu

  
Figure: The Fruit Menu

  
Figure: The Fruit Menu

• A menu can be removed with the

  kill_menu(Menu)

  command. If a menu has submenus, all of the submenus will also be deleted (removed). It is possible to remove a submenu from within a menu (like Fruit above) with this command - so that entries in the top level menu are automatically adjusted

  clear_menu(Menu)

  removes all entries from a menu - although the menu will still exist - but it will contain no items

  disable_menu(Menu)

  The whole menu Menu is disabled - its colour on the menu bar (if it it a top level menu) is 'greyed out' - and all items in it also appear grey

  enable_menu(Menu)

  will enable a previously disabled Menu
• Checking menus

  is_menu(Menu)

  Is to check if Menu exists ... from within the program

  get_menus(Menus)

  Returns a list of current menus in the variable Menus - no indication is provided of whether a menu is in the menu bar, a hierarchical submenu or a popup menu

  
Figure 9: The Fruit Menu - disabled

• It is also possible to add items to menus that already exist - this includes the default menus provided within the MacProlog environment. This is done with the

  extend_menu(Menu,Items)

  for instance, the call

   
  extend_menu('Edit',['Make me coffee'])

  will add a new entry to the existing Edit menu

  
Figure 10: The Edit Menu

  
Figure 11: The Edit Menu - with the additional entry

• Similar to enabling a menu, it is also possible to enable or disable an item within a menu, this is done with

  disable_item(Menu,Item)
  enable_item(Menu,Item)

• Further it possible to rename items within a menu

  rename_item('Eval','Enter','  /T')

  
Figure 12: The Eval Menu

  
Figure 13: The Eval Menu - with the compile and Enter renamed