Problems with property bindings

import QtQuick 2.1
import QtQuick.Window 2.1

Window {
    id: window

    width: 320
    height: 240

    // doesn't matter if it's an alias or not
    readonly property real contentWidth: window.width
    readonly property alias contentHeight: window.height

    Rectangle {
        id: container
        width: window.contentWidth
        height: window.contentHeight

        Rectangle {
            color: "red"
            x: container.width / 2 - width / 2
            y: container.height / 2 - height / 2
            width: window.contentWidth
            height: window.contentHeight

            Text {
                anchors.right: parent.right
                anchors.bottom: parent.bottom
                text: qsTr("(%1,%2 %3x%4)").arg(parent.x).arg(parent.y).arg(parent.width).arg(parent.height)
            }
        }
    }
}