containmentMask documentation should make it clearer that a QtObject can be used

import QtQml
import QtQuick

Window {
    id: window
    visible: true
    width: 640
    height: 480

    Rectangle {
        id: control
        width: 10
        height: 100
        color: tapHandler.pressed ? Qt.darker("#444") : (hoverHandler.hovered ? Qt.lighter("#444") : "#444")
        anchors.centerIn: parent

        TapHandler {
            id: tapHandler
        }
        HoverHandler {
            id: hoverHandler
        }

        containmentMask: QtObject {
            id: mask
            function contains(point: point) : bool {
                let size = 30
                let bounds = Qt.rect((control.width - size) / 2, 0, size, control.height)
                print("hello", point, bounds)
                return point.x >= bounds.x
                    && point.x < bounds.x + bounds.width
                    && point.y >= bounds.y
                    && point.y < bounds.y + bounds.height
            }
        }
    }
}