assertion.swift

    var waveVisualizerTrackingArea: NSTrackingArea!
    var fftVisuzalizerTrackingArea: NSTrackingArea!
    func setupTracking() {
        waveVisualizerTrackingArea = NSTrackingArea(rect: waveVisualizerBox.frame, options: [.activeInActiveApp, .mouseMoved], owner: self, userInfo: nil)
        fftVisuzalizerTrackingArea = NSTrackingArea(rect: fftVisualizerBox.frame, options: [.activeInActiveApp, .mouseMoved], owner: self, userInfo: nil)
        self.view.addTrackingArea(waveVisualizerTrackingArea)
        self.view.addTrackingArea(fftVisuzalizerTrackingArea)
    }
    
    override func mouseMoved(with event: NSEvent) {
        print(event.trackingArea)
    }