How to get notified when NSWindow opens?
appkit, cocoa, nswindow, nswindowcontroller
Solution
By macOS 10.10, this is somewhat solved by the call to `NSViewController`'s `viewWillAppear` or `viewDidAppear`. Have an `NSViewController` subclass and set it as the `contentViewController` of the window. Then its `viewWillAppear`/ `viewDidAppear` implementation can post a notification that the window will (or did) open.
Problem
How to take notice when an `NSWindow` is about to be opened or have just opened? That is, the opposite of `windowWillClose:` delegate method (likewise the opposite of `NSWindowWillCloseNotification.`) This is related to this question, but from the other direction. The background is, I'm looking to couple a window with a tickmark on the main menu (among other things). When the window is shown, the corresponding ̨ menu item should be checked and vice-versa.