I have a background process which is updating an IOSurface-backed CVPixelBuffer at 30fps. I want to render a preview of that pixel buffer in my window, scaled to the size of the NSView that's displaying it. I get a callback every time the pixelbuffer/IOSurface is updated. I've tried using a custom layer-backed NSView and setting the layer contents to the IOsurface -- which works when the view is created but it's never updated unless the window is resized or another window is in front of it. I've tried setting both my view and my layer SetNeedsDisplay(), I've tried changing the layerContentsRedrawPolicy to .onSetNeedsDisplay, I've tried making sure all my content and update code is happening on the UI thread, but I can't get it to dynamically update. Is there a way to bind my layer or view to the IOSurface once and then just have it reflect the updates as they happen, or, if not, at least mark the layer as dirty each frame when it changes? I've pored over the docs but I don't see a lot about the relationship between IOSurface and CALayer.contents, and when in the lifecycle to mark things dirty (especially when updates are happening outside the view). Here's example code: class VideoPreviewThumbnail: NSView, VideoFeedConsumer {   let testCard = TestCardHelper()       override var wantsUpdateLayer: Bool {     get { return true }   }   required init?(coder decoder: NSCoder) {     super.init(coder: decoder)     self.wantsLayer = true     self.layerContentsRedrawPolicy = .onSetNeedsDisplay      		/* Scale the incoming data to the size of the view */      self.layer?.transform = CATransform3DMakeScale(       (self.layer?.contentsScale)! * self.frame.width / CGFloat(VideoSettings.width),       (self.layer?.contentsScale)! * self.frame.height / CGFloat(VideoSettings.height),       CGFloat(1)) 	 /* Register us with the content provider */     VideoFeedBrowser.instance.registerConsumer(self)   }       deinit{     VideoFeedBrowser.instance.deregisterConsumer(self)   }       override func updateLayer() { 		/* ideally we woudln't need to do this */     updateLayer(pixelBuffer: VideoFeedBrowser.instance.renderer.pixelBuffer)   }    	/* This gets called every time our pixelbuffer is updated (30fps) */   @objc   func updateFrame(pixelBuffer: CVPixelBuffer) {     updateLayer(pixelBuffer: pixelBuffer)   }       func updateLayer(pixelBuffer: CVPixelBuffer) {     guard let surface = CVPixelBufferGetIOSurface(pixelBuffer)?.takeUnretainedValue() else {      print("pixelbuffer isn't IOsurface backed! noooooo!")       return;     } 	 /* these don't have any effect */ 	 //		self.layer?.setNeedsDisplay() //		self.setNeedsDisplay(invalidRect: self.visibleRect)     self.layer?.contents = surface   } }