QtQuickView performance problem.

[mano233]

When a QtQuickView is overlaid on other views, the graphics performance drops severely(unless that view is not visible).
**I built on macos 10.15.7 with qt 6.0.0 beta3 and used metalRHI **

In fact, 5.15 also has the same problem, but the fps value cannot be displayed in xcode

qml01.qml

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

Window{
    id:root
    visible: true
    width: 800
    height: 480
    Button{
        onClicked:{
            var component = Qt.createComponent("file:/Users/mano233/Documents/c_projects/untitled3/qml/qml02.qml")
            var window    = component.createObject(root)
            window.show()
        }
    }
}

qml02.qml

import QtQuick 2.15
import QtQuick.Controls 1.0
import QtQuick.Window 2.15

Window {
    visible:true;
    width:720;
    height:640;
    Rectangle{
            width:100;height:100;
            color:"black";
            RotationAnimation on rotation {
                loops: Animation.Infinite
                from: 0
                to: 360
            }
        }
}

main.cpp

#include <Qtqml>
#include <QtGui/QGuiApplication>
#include <QtQuick/QQuickWindow>
#include <QtCore/QUrl>
#include <QDebug>

int main(int argc, char* argv[]){
    QQuickWindow::setGraphicsApi(QSGRendererInterface::MetalRhi);
    QGuiApplication app(argc, argv);
    QQmlApplicationEngine engine;
    const QUrl url("file:/Users/mano233/Documents/c_projects/untitled3/qml/qml01.qml");
    QObject::connect(&engine, &QQmlApplicationEngine::objectCreated,
                     &app, [url](QObject *obj, const QUrl &objUrl) {
                if (!obj && url == objUrl)
                    QCoreApplication::exit(-1);
            }, Qt::QueuedConnection);
    engine.load(url);
    return QGuiApplication::exec();
}

When the views overlap，FPS is 40-45

unless that view is not visible，FPS is 60