implicitWidth/implicitHeight of a non visible layout are null

import QtQuick 2.2
import QtQuick.Controls 1.1
import QtQuick.Layouts 1.1

ApplicationWindow {
    visible: true
    width: 640
    height: 480
    title: qsTr("Hello World")

    RowLayout {
        id: row
        visible: false
        Label { id: label; text: "hello world" }
    }

    Button {
        text: qsTr("press")
        anchors.centerIn: parent
        onClicked: print("w " + row.implicitWidth + " h " + row.implicitHeight + " label width " + label.implicitWidth)
    }
}