Hide / Show the menu item in the main menu of the application by pressing the Option key

Question

I want to add a menu item to the main menu of the application, which will be used quite rarely. I want it to be hidden by default and only show when the user holds the Option key. How to do it?

It seems that I should handle flagsChanged: but is this an NSResponder method and NSMenu not inheriting from NSResponder ? I tried it in the main window controller, and it works when I press the Option key before clicking on the menu. The following usage example does not work: click on a menu item (no item), press the select key - my item will appear, release the option key - the item should disappear.

I also tried NSEvent addLocalMonitorForEventsMatchingMask:handler: and addGlobalMonitorForEventsMatchingMask:handler: for NSFlagsChangedMask , but when the select key is pressed when the main menu is open, neither local nor global handlers start.

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 works when tracking controls, so it does not affect performance too much.

Answer 2

The best way to achieve this is to use two menu items, the first menu item uses a custom view of height 0 and is disabled, and then there is an “alternative” item below it. (You will need to set this keyEquivalentModifierMask element to NSAlternateKeyMask ). With this arrangement, when you press the select key, NSMenu will automatically replace the zero-height menu item with an alternative element that will have the effect of creating the item’s menu in a magical way.

No need for timers, updates or flag change notifications.

This functionality is described in the documentation here: Alternative Management

Answer 3

When creating the menu, an optional element is included and mark it as hidden. Then set the class instance as a menu delegate and add a loop loop observer when the menu is open to control the hidden state of the optional item.

 @implementation AppController { CFRunLoopObserverRef _menuObserver; } - (void)updateMenu { BOOL hideOptionalMenuItems = ([NSEvent modifierFlags] & NSAlternateKeyMask) != NSAlternateKeyMask; [self.optionalMenuItem setHidden:hideOptionalMenuItems]; } - (void)menuWillOpen:(NSMenu *)menu { [self updateMenu]; if (_menuObserver == NULL) { _menuObserver = CFRunLoopObserverCreateWithHandler(NULL, kCFRunLoopBeforeWaiting, true, 0, ^(CFRunLoopObserverRef observer, CFRunLoopActivity activity) { [self updateMenu]; }); CFRunLoopAddObserver(CFRunLoopGetCurrent(), _menuObserver, kCFRunLoopCommonModes); } } - (void)menuDidClose:(NSMenu *)menu { if (_menuObserver != NULL) { CFRunLoopObserverInvalidate(_menuObserver); CFRelease(_menuObserver); _menuObserver = NULL; } } 

Answer 4

Since the NSMenuDelegate menuNeedsUpdate: method is called before display, it can be overridden, check if the [NSEvent modifierFlags] alternative bit is set, and use this to show / hide the secret menu items.

Here is an example copied from Show functionality with key modifiers that covers just this topic:

 #pragma NSMenu delegate methods - (void) menuNeedsUpdate: (NSMenu *)menu { NSLog(@"menuNeedsUpdate: %@", menu); NSUInteger flags = ([NSEvent modifierFlags] & NSDeviceIndependentModifierFlagsMask); // We negate the value below because, if flags == NSAlternateKeyMask is TRUE, that // means the user has the Option key held, and wants to see the secret menu, so we // need shoudHideSecretMenu to be FALSE, so we just negate the value. BOOL shoudHideSecretMenu = !(flags == NSAlternateKeyMask); NSLog(@"Flags: 0x%lx (0x%x), shoudHideSecretMenu = %d", flags, NSAlternateKeyMask, shoudHideSecretMenu); [secretMenuItem setHidden:shoudHideSecretMenu]; } 

Answer 5

There are some complicated answers here, but in fact it is very simple:

Create 2 menu items. The first is the default with any key character and name you want. The second is what will be shown when the modifier key is omitted - again with a separate key and symbol. In the second menu item, turn on "Alternate", and everything else will happen automatically.

The required modifier is determined by comparing two key values.