Implement mirror functionality for QML items

function flipH(flip : bool, width : real) {
    if (flip)
        root.flipHorizontalMat = Qt.matrix4x4(-1, 0, 0, width,
                                                0, 1, 0, 0,
                                                0, 0, 1, 0,
                                                0, 0, 0, 1)
    else
        root.flipHorizontalMat = Qt.matrix4x4()
}

function flipV(flip : bool, height : real) {
    if (flip)
        root.flipVerticalMat = Qt.matrix4x4(1, 0, 0, 0,
                                            0, -1, 0, height,
                                            0, 0, 1, 0,
                                            0, 0, 0, 1)
    else
        root.flipVerticalMat = Qt.matrix4x4()
}