Repaint NSView when mainWindow changes

Question

I would like to change the background of an NSView depending on if the the window is focused.

I found this question: Change NSView background color when window has focus

And the first answer works fine except the redraw is not triggered when the windows loses or gains focus.

How can I trigger the redraw when the mainWindow changes?

Answer 1

In your NSWindow delegate:

func windowDidBecomeMain(notification: NSNotification) {
    let theView = ...
    theView.needsDisplay = true
}

func windowDidResignMain(notification: NSNotification) {
    let theView = ...
    theView.needsDisplay = true
}

In your NSView subclass:

func drawRect(rect: NSRect) {
    if self.window.isMainWindow {
        // draw active appearance
    } else {
        // draw inactive appearance
    }
}

Answer 2

Use NSNotificationCenter's addObserver:selector:name:object: or addObserverForName:object:queue:usingBlock: to watch for NSWindowDidBecomeMainNotification and NSWindowDidResignMainNotification with the view's window as the object argument.