Being apprised of when NSStatusItem is hidden

Question

I have an app which uses an NSStatusItem. On small screens there\'s not much space in the status bar. When a user switches to an application with a lot of menu

Answer 1

It's pretty smart of you to realize that when a status item is hidden, its window will be moved into the background.

Now the notification you're looking for is: NSWindowDidResignKeyNotification (or NSWindowDidResignMainNotification depending on the context of your application)

For a clear explanation about the difference between a key window and a main window, see this.