test of https://stackoverflow.com/questions/50160614/how-to-use-grabwindow

main.qml

import QtQuick 2.9
Rectangle{
    color: "blue"
    anchors.fill: parent
    radius: width/2
    Text {
        text: Qt.formatTime(new Date(), "hh:mm:ss")
        anchors.centerIn: parent
    }
}