// main.cpp

#include <QGuiApplication>
#include <QQmlApplicationEngine>
#include <QQuickWindow>

int main(int argc, char *argv[])
{
    qputenv("QSG_RENDER_LOOP", QByteArrayLiteral("threaded"));
#if QT_VERSION < QT_VERSION_CHECK(6, 0, 0)
    QCoreApplication::setAttribute(Qt::AA_EnableHighDpiScaling);
#endif

    QGuiApplication app(argc, argv);

    QQmlApplicationEngine engine;
    const QUrl url(QStringLiteral("qrc:/main.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);

    QQuickWindow *w = qobject_cast<QQuickWindow *>(engine.rootObjects()[0]);
    //###########################################
#if QT_VERSION > QT_VERSION_CHECK(6, 0, 0)
    w->setPersistentGraphics(false);
#else 
    w->setPersistentOpenGLContext(false); 
#endif
    w->setPersistentSceneGraph(false);
    //###########################################
    return app.exec();
}

//main.qml

import QtQuick 2.12
import QtQuick.Window 2.12

Window {
    id: root
    width: 640
    height: 480
    visible: true
    title: qsTr("Hello World")

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

        Component.onCompleted: anim.start()
    }

    OpacityAnimator {
        id: anim

        target: rect
        from: 1
        to: 0
        duration: 20000
    }

    MouseArea {
        anchors.fill: parent

        onPressed: {
            root.hide()
            timer.start()
        }
    }

    Timer {
        id: timer
        interval: 2000
        onTriggered: {
            root.show()
        }

    }
}