mousedown.swift

    //Creating the view
    override func mouseDown(with event: NSEvent) {
        let click = event.locationInWindow
        let point = self.convert(click, from: nil)
        self.addDot(at: point)
        
        NotificationCenter.default.post(name: .pointsChanged, object: nil)
    }
    
    func addDot(at locationInView: CGPoint) {
        let dot = DotView(frame: NSRect(origin: .zero, size: pointSize))
        dot.center = locationInView
        dot.number = self.subviews.count
        self.addSubview(dot)
    }
    
    //The mouse methods in the subview
    override func mouseDown(with event: NSEvent) {
        location = self.frame.origin
    }
    
    override func mouseDragged(with event: NSEvent) {
        self.center = self.superview!.convert(event.locationInWindow, from: nil)
    }
    
    override func mouseUp(with event: NSEvent) {
        location = self.frame.origin
        nextResponder?.mouseUp(with: event)
    }