How can I create a new window from within QML?

Is there a way to create a completely new window instance, as a child window of the main QML window in a QmlApplication?

// ChildWindow.qml
Rectangle {
    id: childWindow
    width: 100
    height: 100
    // stuff
}

// main.qml
Rectangle {
    id: window
    width: 1000
    height: 600

    MouseArea {
        anchors.fill: parent
        onClicked: createAWindow(childWindow);
    }
}

I am trying to avoid writing a Q_OBJECT class just for instanciating the new window within a new QmlApplicationViewer.

There is no way to create top-level windows using only built-in QML functionality.

However there's a project on Qt Labs called Desktop Components, which among other things contains a Window component, which allows you to create new top-level windows.