import QtQuick

Window {
    id: root
    width: 640
    height: 480
    visible: true
    title: qsTr("Hello World")

    readonly property bool active: root.dragHandler.active
    property DragHandler dragHandler: DragHandler {}
}

Warning: main.qml:10:53: Could not compile binding for active: Member active of QQuickDragHandler of (component in /home/prcs1076/tmp/untitled/build/main.qml)::dragHandler 
with type QQuickDragHandler can be shadowed [compiler]

    readonly property bool active: root.dragHandler.active