visible propertie doesn't effect with DropShadow effect.

import Qt 4.6
Rectangle {
    width: 500
    height: 500
    Rectangle {
        id: rect
        width: 200; height: 300; border.width: 1
        anchors.centerIn: parent
        MouseRegion {
            anchors.fill: parent
            hoverEnabled: true
            onClicked: {
                test.visible = test.visible ? false : true;
            }
        }
//            effect: DropShadow {
//                yOffset: 5
//                xOffset: 5
//                blurRadius: 16
//            }

        Rectangle {
            id: test
            anchors.bottom: parent.bottom
            anchors.right: parent.right
            anchors.rightMargin: 2
            anchors.bottomMargin: 2

            width: 10
            height: 10
            visible: false
            color: 'black'
        }
    }
}