import Cocoa

class ViewController: NSViewController {

    @IBOutlet weak var label: NSTextField!
    var monitor: Any?
    
    override func viewDidLoad() {
        super.viewDidLoad()
    }
    
    override func viewDidAppear() {
        monitor = NSEvent.addLocalMonitorForEvents(matching: NSEvent.EventTypeMask.pressure) { (event) -> NSEvent? in
            DispatchQueue.main.async {
                self.label.stringValue = "pressure: \(round(100 * event.pressure) / 100)"
            }
            return event
        }
    }
    
    override func viewWillDisappear() {
        if let monitor = monitor {
            NSEvent.removeMonitor(monitor)
        }
    }

    override var representedObject: Any? {
        didSet {
        }
    }
    
}