In Cocoa/AppKit, given a screen from [NSScreen screens], how can I find out if there's a full-screen app running on that specific screen? I'm mostly interested in apps that use the Cocoa APIs for full-screen, but if there's a solution that also encompasses other types of full-screen apps, even better. The solution needs be able to pass Mac App Store approval.
My specific use case involves a menu bar app (NSStatusItem) and figuring out whether or not a menubar is shown at all on [NSScreen mainScreen] in order to allow a global keyboard shortcut to show either a popover positioning on the status item (if it's visible) or a floating window if there's no visible status item.
NSScreens themselves don't seem to expose any information about windows/apps, and NSRunningApplication doesn't expose this information either.
Are there perhaps Carbon APIs for finding this out? For example, if I have a list of windows, I could iterate through them and see if any window frames match the screens' frame exactly. On the other hand, there might be apps that have a frame like that but run underneath other apps (like the Backdrop app, https://itunes.apple.com/us/app/backdrop/id411461952?mt=12), so an approach like this would need to look at window levels.
You can try the CGWindowList API, such as CGWindowListCopyWindowInfo().
If you just want to know if the menu bar is showing, you should be able to check -[NSApplication currentSystemPresentationOptions] for NSApplicationPresentationAutoHideMenuBar or NSApplicationPresentationHideMenuBar. That method can also tell you if the active app is in Cocoa full-screen mode (NSApplicationPresentationFullScreen).