import QtQuick 2.10
import QtQuick.Window 2.2
import QtQuick.Shapes 1.0
import QtGraphicalEffects 1.0

Window {
    visible: true
    width: 640
    height: 480
    id: root
    color: "green"

    Item {
        id: i
        width: parent.width * 0.2
        height: width
        anchors.right: parent.right
        anchors.top: parent.top

        Rectangle {
            id: a
            visible: false
            anchors.fill: parent
            color: 'blue'
        }

        Rectangle {
            id: d
            anchors.centerIn: parent
            width: parent.width * 0.5
            height: parent.height * 0.5
            visible: false
            color: "firebrick"
            opacity: 1.0
        }


        OpacityMask {
            visible: true
            anchors.fill: a
            source: a
            maskSource: d
        }
    }
}