TextInput's positionToRectangle() reports weird x-values

Rectangle {
    width: 640; height: 480;
    Rectangle {
        anchors.centerIn: parent
        width: 400; height: 25;
        color: "blue"

        TextInput {
            anchors.fill: parent
            color: "white"
            focus: true
            text: "Sea Shepherd campaigner Peter Bethune faces 15 years in jail after boarding whaling ship"

            MouseArea {
                anchors.fill: parent
                onPositionChanged: { var rect = parent.positionToRectangle(mouse.x); print("positionToRectangle(mouseX).x: "
                            + rect.x + ", y: " + rect.y + ", width: " + rect.width + ", height: " + rect.height); }
            }
        }
    }
}