Question

I want to add a menu item into the application’s main menu that will be used quite rare. I want it to be hidden by default and show it only when user hold down Option key. How do i do this?

It seems that I should handle flagsChanged:, but it is NSResponder‘s method and NSMenu does not inherits from NSResponder? I tried it inside main window controller, and it works when I press Option key before I click on menu. The following use case doe not work: click on menu item (there is no item), press option key — my item should appear, release option key — item should disappear.

I’ve also tried NSEvent’s addLocalMonitorForEventsMatchingMask:handler: and addGlobalMonitorForEventsMatchingMask:handler: for NSFlagsChangedMask but when option key pressed while main menu is open neither local or global handlers are not fired.

How can I do this?

Answer 1

Add the following to applicationDidFinishLaunching.

// Dynamically update QCServer menu when option key is pressed
NSMenu *submenu = [[[NSApp mainMenu] itemWithTitle:@"QCServer"] submenu];    
NSTimer *t = [NSTimer timerWithTimeInterval:0.1 target:self selector:@selector(updateMenu:) userInfo:submenu repeats:YES];
[[NSRunLoop currentRunLoop] addTimer:t forMode:NSEventTrackingRunLoopMode];

then add

- (void)updateMenu:(NSTimer *)t {

    static NSMenuItem *menuItem = nil;
    static BOOL isShowing = YES;

    // Get global modifier key flag, [[NSApp currentEvent] modifierFlags] doesn't update while menus are down
    CGEventRef event = CGEventCreate (NULL);
    CGEventFlags flags = CGEventGetFlags (event);
    BOOL optionKeyIsPressed = (flags & kCGEventFlagMaskAlternate) == kCGEventFlagMaskAlternate;
    CFRelease(event);

    NSMenu *menu = [t userInfo];

    if (!menuItem) {
        // View Batch Jobs...
         menuItem = [menu itemAtIndex:6];
        [menuItem retain];
    }

    if (!isShowing && optionKeyIsPressed) {
        [menu insertItem:menuItem atIndex:6];
        [menuItem setEnabled:YES];
        isShowing = YES;
    } else if (isShowing && !optionKeyIsPressed) {
        [menu removeItem:menuItem];
        isShowing = NO;
    }

    NSLog(@"optionKeyIsPressed %d", optionKeyIsPressed);
}

The timer only fires while controls are being tracked so it’s not too much of a performance hit.