[QML][Layout] top/bottomMargin with fillHeight components

Hi,

I'm facing a problem regarding top / bottom margin on components inside a layout (GridLayout here, but it seems to be the same with a ColumnLayout) with fillHeight.

Considering the following example :

import QtQuick 2.0
import QtQuick.Layouts 1.2

Item {
    width : 800
    height : 480
    GridLayout {
        anchors.fill: parent
        columns: 2
        rows : 2
        Rectangle {
            color:"red"
            Layout.fillHeight: true
            width : 400
        }
        Rectangle {
            color:"green"
            Layout.rowSpan: 2
            Layout.fillHeight: true
            width : 400
        }
        Rectangle {
            color:"blue"
            Layout.fillHeight: true
            width : 400
            Layout.bottomMargin: 10
        }
    }
}

The display is as WithBottom.jpg.

Just commenting the line "Layout.bottomMargin: 10" restablish the ratio between red and blue rectangles (see WithoutBottom.jpg).

There seem to be a ratio calculated that take into account the margins when my guess is that it shouldn't. Indeed, the height of the blue rectangle seems to be (top+bottom margins)*height of the red one (I've tested with like a dozen values, maybe not enough).