(OS X) Detect when front application enters full screen mode

Question

I am writing a UIElement application that displays a status window on the screen side, similar to the Dock.

Now that the program takes over the entire screen, I need to hide my status window, like the Dock.

What are my possibilities for detecting this and the reverse event?

I like to avoid polling for a timing event, and also cannot use undocumented tricks (like the one suggested here )

What does not work:

• Registering the Carbon event handler for the kEventAppSystemUIModeChanged event kEventAppSystemUIModeChanged insufficient - it works to determine the full-screen mode of VLC, but not for modern Cocoa applications that use the new full-screen widgets in the upper right corner of their windows.

• Similarly, the following Apple instructions on the NSApplication presentationOptions API by monitoring changes to the currentSystemPresentationOptions property do not help - again, it only informs about VLC full screen mode, but not about applications that use the "top right full screen window" widget.

• Monitoring screen configuration changes with CGDisplayRegisterReconfigurationCallback does not work because there are no callbacks for these full-screen modes.

Answer 1

Based on @Chuck's suggestion, I came up with a solution that works somewhat, but cannot be reliable.

The solution is based on the assumption that the new full-screen mode for windows 10.7 transfers these windows to a new screen space. Therefore, we subscribe to notifications of changes in the active space. In this notification handler, we check the list of windows to determine if the menu bar is enabled. If this is not the case, it probably means that we are in full-screen space.

Checking for the presence of the Menubar window is the best test I could find based on Chuck's idea. I don’t like it very much because it makes assumptions about the names and the presence of internal managed windows.

Here's the test code that goes into AppDelegate.m, which also includes a test for another full-screen mode in the application:

 - (void)applicationDidFinishLaunching:(NSNotification *)aNotification { NSApplication *app = [NSApplication sharedApplication]; // Observe full screen mode from apps setting SystemUIMode // or invoking 'setPresentationOptions' [app addObserver:self forKeyPath:@"currentSystemPresentationOptions" options:NSKeyValueObservingOptionNew context:NULL]; // Observe full screen mode from apps using a separate space // (ie those providing the fullscreen widget at the right // of their window title bar). [[[NSWorkspace sharedWorkspace] notificationCenter] addObserverForName:NSWorkspaceActiveSpaceDidChangeNotification object:NULL queue:NULL usingBlock:^(NSNotification *note) { // The active space changed. // Now we need to detect if this is a fullscreen space. // Let look at the windows... NSArray *windows = CFBridgingRelease(CGWindowListCopyWindowInfo (kCGWindowListOptionOnScreenOnly, kCGNullWindowID)); //NSLog(@"active space change: %@", windows); // We detect full screen spaces by checking if there a menubar // in the window list. // If not, we assume it in fullscreen mode. BOOL hasMenubar = NO; for (NSDictionary *d in windows) { if ([d[@"kCGWindowOwnerName"] isEqualToString:@"Window Server"] && [d[@"kCGWindowName"] isEqualToString:@"Menubar"]) { hasMenubar = YES; break; } } NSLog(@"fullscreen: %@", hasMenubar ? @"No" : @"Yes"); } ]; } - (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context { if ([keyPath isEqual:@"currentSystemPresentationOptions"]) { NSLog(@"currentSystemPresentationOptions: %@", [change objectForKey:NSKeyValueChangeNewKey]); // a value of 4 indicates fullscreen mode } }