Menu Class (Typed)

Object
  VObject
    Menu

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Menus provide the highest level of user control within an application. At the most basic level, a menu is series of items that are displayed in the menu bar (for example, the strings "OpenFile", a question mark bitmap to indicate help, and so on.) When selected, these items perform an action—for example, open a file, exit the application, or get help. The items in a menu bar might also contain a submenu as another type of item. When creating a submenu, you generally specify a title (this is the text that appears in the menu bar) and the set of items that belong to that submenu (the items are displayed when the title is activated in the menu bar). For example, a submenu might have the title "File" and items named "Open," "Save," and "Exit." Like menus, submenus can contain strings, bitmaps, and other menus. Using submenus allows you to have multi-dimensional menus. In addition, just like any menu, they can be created from a resource entity. Each item on a menu is identified by a unique ID. You can then use that ID to refer to the item later in your program (for example, to disable or delete an item). Menu commands can be selected with the mouse or with an accelerator key, and can be added, deleted, inserted, and appended as required. Items on a menu can be dimmed (or grayed) to indicate that they are disabled, and they can be checked to indicate that they are enabled/selected. You can also add separators to a menu. (A separator is a single line inserted between items on a submenu to group similar commands together.) A menu is usually associated with an accelerator table that defines shortcuts (like Ctrl+S for File Save) and a toolbar that provides certain buttons issuing commonly used menu commands. The toolbar and accelerators are usually carried by the menu; assigning a menu to a window automatically assigns the toolbar and accelerators as well. Menus in X# generate the following events—MenuInitEvent, MenuSelectEvent, and MenuCommandEvent. They are dispatched to the window that owns the menu that generated the event. The event handler methods for these events are as follows: Window:MenuInit() is called before a menu is displayed. Window:MenuSelect() is called when a menu command is highlighted. When the user selects a menu command for execution, the window method that matches the menu command's name is called, if any. If there is no matching method, Window:MenuCommand() is called. Menu commands are also propagated up the window ownership hierarchy. For an in depth discussion of how command events are used, refer to the Programmer's Guide. In the Windows, menus are normally created in resource entities. (You can also construct menus dynamically using the Append... or Insert... methods of Menu.) For example, in Windows, menus can be created in a resource entity as follows: The easiest way to construct a menu is by using the Menu Editor. It generates the resource, as illustrated in the example above, as well as the subclass used to instantiate the menu, the accelerator table, and the toolbar.