Cannot draw a single rectangle at constant 60fps

Charby

I was curious about the fps performance versus element type so I wrote a simple test program to display a number of elements (Canvas, QuickPaintedItem, QNanoPainter, QuickItem...)...
Doing this, I experienced that drawing a single Rectangle was not always showing a 60fps : when window is getting large enough (more than 2000x2000), the fps suddenly drops to 35-40 fps.
In addition, It happens in rare occasion I could reach full screen dimension (3840x2160) with a steady 60fps.

Tested with Debian bullseye, Qt5.15.2, Nvidia GeForce GTX 1060 6GB

Here is the QML document for a single Rectangle :

import QtQuick 2.15
import QtQuick.Window 2.15
import QtQuick.Controls 2.2

Window {
    id:window
    width: 640
    height: 480
    onWidthChanged: console.log("width : " + width  )
    onHeightChanged: console.log("height : " + height  )
    visible: true
    title: qsTr("Test FPS")

    Rectangle{
        anchors.fill:parent
        color:"red"

        Control{
            id: fpsMeter
            property int frameCounter: 0
            property int frameCounterAvg: 0
            property int counter: 0
            property real fps: 0
            property real fpsAvg: 0
            implicitWidth :100
            implicitHeight:20

            Item {
                anchors.fill: parent
                NumberAnimation on rotation {
                    from:0; to: 360; duration: 800; loops: Animation.Infinite
                }
                onRotationChanged: fpsMeter.frameCounter++;
            }

            Label {
                anchors.fill: parent
                text: "Ø " + fpsMeter.fpsAvg.toFixed(1) + " | " + fpsMeter.fps.toFixed(1) + " fps"
            }

            Timer {
                interval: 1000; repeat: true; running: true
                onTriggered: {
                    fpsMeter.frameCounterAvg += fpsMeter.frameCounter;
                    fpsMeter.fps = fpsMeter.frameCounter / interval * 1000;
                    fpsMeter.counter++;
                    fpsMeter.frameCounter = 0;
                    if (fpsMeter.counter >= 10) {
                        fpsMeter.fpsAvg = fpsMeter.frameCounterAvg/(interval / 1000 * fpsMeter.counter)
                        fpsMeter.frameCounterAvg = 0;
                        fpsMeter.counter = 0;
                    }
                }
            }
        }
    }
}

Do you have feedbacks about known limitations/issues or simply things I could do wrong (I have tried to analyse it with qml profiler but without finding the potential bottleneck) ?

Charby

Just find out that since a recent OS upgrade the hardware acceleration was not activated on my device, installing nvidia driver fixed this issue.