Determine whether a full screen application is currently active, and get notifications when switching between full screen apps and regular Spaces.
This little library is the result of much banging of foreheads and gnashing of teeth — Mac OS X Lion and OS X Mountain Lion do not expose this information in a particularly direct way.
Add MDCFullScreenDetector.h and MDCFullScreenDetector.m to your project. Add a new NSWindow to your MainMenu.xib and change its class to MDCFullScreenDetector.
Full screen detection does not work if your application has LSUIElement (displayed in Xcode as “Application is agent (UIElement)”) set to YES in its Info.plist.
MDCFullScreenDetector will log a warning message if it detects this condition.
Workaround: call [NSApp setActivationPolicy:NSApplicationActivationPolicyProhibited] in your AppDelegate's applicationDidFinishLaunching: method.
MDCFullScreenDetector posts two notifications to [NSNotificationCenter defaultCenter]:
kMDCFullScreenDetectorSwitchedToFullScreenApp, when switching to a full screen appkMDCFullScreenDetectorSwitchedToRegularSpace, when switching to a regular Space
When switching between two full screen apps, or two regular Spaces, no notification will be posted. If you need to know this, listen for NSWorkspaceActiveSpaceDidChangeNotification and check fullScreenAppIsActive (see Methods, below).
- (BOOL)fullScreenAppIsActive — returns YES if a full screen app is currently active, and NO if a regular Space is currently active.
Although the demo is currently Mountain Lion only, the library itself should work fine on Lion (todo: actually test it).
Open the included Xcode project and run FullScreenDetector. Notifications will pop up in Notification Center when switching between full screen apps and regular Spaces.
All of the code here was written by @shinypb. I hereby release it into the public domain, although I'd love to hear what you build with it.
Special thanks to @anathemalie and @siegel for listening to me complain about this for so long, and @skid for his kind but ultimately unsuccessful suggestion. :)