import QtQuick

Window {
    width: 640
    height: 480
    visible: true

    Rectangle { // could be Item as well
        width: 400
        height: 400
        color: "red"
        layer.enabled: mouseArea.containsMouse
    }
    
    MouseArea {
        id: mouseArea
        width: 400
        height: 400
        hoverEnabled: true
    }
}