[Interest] mapToItem usage and behaviour

[Federico Buti]

Hi all.

Reading the documentation for mapToItem/mapFromItem functions I've
understand that it is possibile to translate a point to/from the coordinate
system of the item itself. In particular, given the signature:

<itemName>.mapToItem(null, 0, 0)


it is possibile to map the coordinate system origin of the item to the
coordinate system of the top level window.


This seems to work, as long as I don't use a Window, i.e. the
following example gives different results (or correct ones which I
cannot understand?):


import QtQuick 2.4

import QtQuick.Window 2.2


Window {

    visible: true

    width: 600

    height: 600

    Rectangle {

        id: rec1

        x: 200

        y: 200

        width: 200

        height: 200

        color: "green"

        opacity: 0.5

        Component.onCompleted: {

            var coords = rec1.mapToItem(null, 0, 0)

            console.log("rec1: " + coords.x + "," + coords.y)

        }

    }

    Rectangle {

        id: rec2

        anchors.centerIn: parent

        width: 200

        height: 200

        color: "blue"

        opacity: 0.5

        Component.onCompleted: {

            var coords = rec2.mapToItem(null, 0, 0)

            console.log("rec2: " + coords.x + "," + coords.y)

        }

    }

}


The resulting coordinates are:


qml: rec2: -100,-100

qml: rec1: 200,200


whereas I expected both rectangles to be at (200, 200). Window is not
an Item, I know. Is this behaviour correct and I'm missing something
trivial? Can the coordinates be traslated as expected?


Thanks in advance,

F.
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