Our MacOS application has a single window which is occupied by an NSView-derived view. It's been working for the last ten years or so, but when using the Sonoma beta, window updates are badly broken. We rely on using setNeedsDisplayInRect to redisplay any portions of the view that need to be redisplayed, but no matter how small a rectangle we specify, the entire window is repainted with the background colour before our drawRect implementation is called. We already provide an overload of isOpaque in our view which returns true, and in the past this was effective for suppressing the background fill, but it no longer seems to work (although I can confirm that it is still called along the way). I've attached an image that shows an example of how a sample window looks after resizing (which is correct) and then what it looks like after using setNeedsDisplayInRect to invalidate the region occupied by the button in the centre. I've explicitly set the NSWindow background colour to blue to make it more obvious : Is it still possible to inhibit the background fill? Repainting the entire view for every update is not really an option for us, for performance reasons