Performance troubles

Question

I have trouble with this simple application. It will respond very slowly (processor usage is over 90%) if I have background picture or just pure Rectangle (id: background in example bellow) before button, if I comment this background rectangle, application would react quickly, but if I add "enable.layers: true" to root item, slow response would be come back . Where is the problem?

I would like to have background picture and fast response on clicking. I am running this example on Raspberry Pi 3.

import QtQuick 2.3


Item {
    id: root
    visible: true
    width: 800
    height: 480


    Rectangle {
        id: background
        anchors.fill: parent
        smooth: true

    }


    Rectangle {
        id: button
        width: 200 ; height: 123

        anchors.centerIn: parent

        smooth: true
        radius: 8

        //color the button with a gradient
        gradient: Gradient {
            GradientStop {
                position: 1.0
                color: {
                    if (mouseArea.pressed)
                        return "red"
                    else
                        return "chartreuse"
                }
            }
            GradientStop {position: 0.0; color: "paleturquoise" }
        }


        MouseArea {
            id:mouseArea
            anchors.fill: parent
            onPressed: {
                //handler.turnOn()
            }
            onReleased: {
               // handler.turnOff()
            }

        }
    }
}

Answer 1

It solved this problem with enabling experimental GL under raspi-config. Reason why QtQuick 1.1 worked OK was due this fact: "In Qt 5, all QML applications are rendered with an OpenGL scenegraph architecture rather than the Graphics View framework used in Qt 4."