QQmlListProperty count/size/length is a non-notifying property

        MultiPointTouchArea {
            id: mpta
            touchPoints: [
                TouchPoint { property color color: "red" },
                TouchPoint { property color color: "orange" },
                TouchPoint { property color color: "lightsteelblue" },
                TouchPoint { property color color: "green" }
            ] }

        Repeater {
            model: mpta.touchPoints.count
 ...
        }