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Views in Menu Items

In Mac OS X v10.5, the NSMenuItem class is enhanced to allow you to include views in the menu item. This article describes the feature.

In Mac OS X v10.5, you can set the view for a menu item using NSMenuItem's setView: method (by default, a menu item has a nil view)—note, though, that menu item views are not supported in the Dock menu. The following code fragment illustrates how you can create a new menu and add it to your application’s menu bar

NSMenuItem* menuBarItem = [[NSMenuItem alloc]

                        initWithTitle:@"Custom" action:NULL keyEquivalent:@""];

// title localization is omitted for compactness

NSMenu* newMenu = [[NSMenu alloc] initWithTitle:@"Custom"];

[menuBarItem setSubmenu:newMenu];

[newMenu release];

[[NSApp mainMenu] insertItem:menuBarItem atIndex:3];

[menuBarItem release];

/*

 Assume that myView1 and myView2 are existing view objects;

 for example, you may have created them in a NIB file.

 */

NSMenuItem* newItem;

newItem = [[NSMenuItem alloc]

               initWithTitle:@"Custom Item 1"

               action:@selector(menuItem1Action:)

               keyEquivalent:@""];

[newItem setView: myView1];

[newItem setTarget:self];

[newMenu addItem:newItem];

[newItem release];

newItem = [[NSMenuItem alloc]

               initWithTitle:@"Custom Item 2"

               action:@selector(menuItem2Action:)

               keyEquivalent:@""];

[newItem setView: myView2];

[newItem setTarget:self];

[newMenu addItem:newItem];

[newItem release];

A menu item with a view does not draw its title, state, font, or other standard drawing attributes, and assigns drawing responsibility entirely to the view. Keyboard equivalents and type-select continue to use the key equivalent and title as normal.

A view in a menu item can receive all mouse events as normal, but keyboard events are not supported. During “non-sticky” menu tracking (that is, manipulating menus with the mouse button held down), a view in a menu item receives mouseDragged: events.

You can add animation to a menu item view as you would any other view (you set a timer to call setNeedsDisplay: or display), but because menu tracking occurs in the NSEventTrackingRunLoopMode, you must add the timer to the run loop in that mode.

When the menu is opened, the view is added to a window; when the menu is closed the view is removed from the window. If you are using a custom view, you can therefore override viewDidMoveToWindow as a convenient place to start or stop animation, reset tracking rectangles and so on, but you should not attempt to move or otherwise modify the window

A menu item with a view sizes itself according to the view's frame, and the width of the other menu items. The menu item will always be at least as wide as its view, but it may be wider. If you want your view to auto-expand to fill the menu item, then make sure that its autoresizing mask has NSViewWidthSizable set. A menu item will resize itself as the view's frame changes, but resizing during menu tracking is not supported.

When a menu item is copied using NSCopying, any attached view is copied using archiving and unarchiving.

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