its drawing to the refresh rate of the display. class CADisplayLink: NSObject { var preferredFramesPerSecond: Int init(target: Any, selector sel: Selector) func add(to runloop: RunLoop, forMode mode: RunLoop.Mode) func invalidate() }
CADisplayLink typealias Failure = Never var runLoop: RunLoop var mode: RunLoop.Mode var preferredFramesPerSecond: Int func receive<S: Subscriber>(subscriber: S) where Failure == S.Failure, Output == S.Input { #warning("TODO:") } } }