Modernize the rendercontrol_opengl example

Make it work when using QRhi-on-OpenGL.

Some features like demonstrating a dedicated render thread, or targeting
the window with the Quick content ('onscreen' argument, not clear why
that was added in the first place), are now removed. Some of these could
be reintroduced in future examples, not necessarily in combination with
OpenGL. For now they are removed since the cost of porting and
maintaining all that is not reasonable at this point.

Task-number: QTBUG-84040
Change-Id: I67e5c7cc835c5cf5653cf827004ce66a4d300b36
Reviewed-by: Eirik Aavitsland <eirik.aavitsland@qt.io>

7 files changed, 68 insertions, 710 deletions

diff --git a/examples/quick/rendercontrol/rendercontrol_opengl/CMakeLists.txt b/examples/quick/rendercontrol/rendercontrol_opengl/CMakeLists.txt
index fb1c6ecf12..310f721f2e 100644
--- a/examples/quick/rendercontrol/rendercontrol_opengl/CMakeLists.txt
+++ b/examples/quick/rendercontrol/rendercontrol_opengl/CMakeLists.txt
@@ -15,16 +15,17 @@ find_package(Qt6 COMPONENTS Core)
 find_package(Qt6 COMPONENTS Gui)
 find_package(Qt6 COMPONENTS Quick)
 find_package(Qt6 COMPONENTS Qml)
+find_package(Qt6 COMPONENTS OpenGL)
 
 add_qt_gui_executable(rendercontrol_opengl
     cuberenderer.cpp cuberenderer.h
     main.cpp
-    window_multithreaded.cpp window_multithreaded.h
     window_singlethreaded.cpp window_singlethreaded.h
 )
 target_link_libraries(rendercontrol_opengl PUBLIC
     Qt::Core
     Qt::Gui
+    Qt::OpenGL
     Qt::Qml
     Qt::Quick
 )
diff --git a/examples/quick/rendercontrol/rendercontrol_opengl/main.cpp b/examples/quick/rendercontrol/rendercontrol_opengl/main.cpp
index 71903045cc..7a24d70ec5 100644
--- a/examples/quick/rendercontrol/rendercontrol_opengl/main.cpp
+++ b/examples/quick/rendercontrol/rendercontrol_opengl/main.cpp
@@ -49,38 +49,19 @@
 ****************************************************************************/
 
 #include <QGuiApplication>
-#include <QCommandLineParser>
-#include <QCommandLineOption>
+#include <QQuickWindow>
 #include "window_singlethreaded.h"
-#include "window_multithreaded.h"
 
 int main(int argc, char **argv)
 {
     QGuiApplication app(argc, argv);
 
-    QCoreApplication::setApplicationName("Qt Render Control Example");
-    QCoreApplication::setOrganizationName("QtProject");
-    QCoreApplication::setApplicationVersion(QT_VERSION_STR);
-    QCommandLineParser parser;
-    parser.setApplicationDescription(QCoreApplication::applicationName());
-    parser.addHelpOption();
-    parser.addVersionOption();
-    QCommandLineOption threadedOption("threaded", "Threaded Rendering");
-    parser.addOption(threadedOption);
+    // only functional when Qt Quick is also using OpenGL
+    QQuickWindow::setSceneGraphBackend(QSGRendererInterface::OpenGLRhi);
 
-    parser.process(app);
-
-    QScopedPointer<QWindow> window;
-    if (parser.isSet(threadedOption)) {
-        qWarning("Using separate Qt Quick render thread");
-        window.reset(new WindowMultiThreaded);
-    } else {
-        qWarning("Using single-threaded rendering");
-        window.reset(new WindowSingleThreaded);
-    }
-
-    window->resize(1024, 768);
-    window->show();
+    WindowSingleThreaded window;
+    window.resize(1024, 768);
+    window.show();
 
     return app.exec();
 }
diff --git a/examples/quick/rendercontrol/rendercontrol_opengl/rendercontrol_opengl.pro b/examples/quick/rendercontrol/rendercontrol_opengl/rendercontrol_opengl.pro
index 900f5d14dd..3f32a0dff4 100644
--- a/examples/quick/rendercontrol/rendercontrol_opengl/rendercontrol_opengl.pro
+++ b/examples/quick/rendercontrol/rendercontrol_opengl/rendercontrol_opengl.pro
@@ -1,14 +1,12 @@
 TEMPLATE = app
 
-QT += quick qml
+QT += quick qml opengl
 
 SOURCES += main.cpp \
            window_singlethreaded.cpp \
-           window_multithreaded.cpp \
            cuberenderer.cpp
 
 HEADERS += window_singlethreaded.h \
-           window_multithreaded.h \
            cuberenderer.h
 
 RESOURCES += rendercontrol.qrc
diff --git a/examples/quick/rendercontrol/rendercontrol_opengl/window_multithreaded.cpp b/examples/quick/rendercontrol/rendercontrol_opengl/window_multithreaded.cpp
deleted file mode 100644
index 01d6b8b5b2..0000000000
--- a/examples/quick/rendercontrol/rendercontrol_opengl/window_multithreaded.cpp
+++ /dev/null
@@ -1,454 +0,0 @@
-/****************************************************************************
-**
-** Copyright (C) 2017 The Qt Company Ltd.
-** Contact: https://www.qt.io/licensing/
-**
-** This file is part of the examples of the Qt Toolkit.
-**
-** $QT_BEGIN_LICENSE:BSD$
-** Commercial License Usage
-** Licensees holding valid commercial Qt licenses may use this file in
-** accordance with the commercial license agreement provided with the
-** Software or, alternatively, in accordance with the terms contained in
-** a written agreement between you and The Qt Company. For licensing terms
-** and conditions see https://www.qt.io/terms-conditions. For further
-** information use the contact form at https://www.qt.io/contact-us.
-**
-** BSD License Usage
-** Alternatively, you may use this file under the terms of the BSD license
-** as follows:
-**
-** "Redistribution and use in source and binary forms, with or without
-** modification, are permitted provided that the following conditions are
-** met:
-**   * Redistributions of source code must retain the above copyright
-**     notice, this list of conditions and the following disclaimer.
-**   * Redistributions in binary form must reproduce the above copyright
-**     notice, this list of conditions and the following disclaimer in
-**     the documentation and/or other materials provided with the
-**     distribution.
-**   * Neither the name of The Qt Company Ltd nor the names of its
-**     contributors may be used to endorse or promote products derived
-**     from this software without specific prior written permission.
-**
-**
-** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
-** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
-** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
-** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
-** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
-** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
-** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
-** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
-** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
-** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
-** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
-**
-** $QT_END_LICENSE$
-**
-****************************************************************************/
-
-#include "window_multithreaded.h"
-#include "cuberenderer.h"
-#include <QOpenGLContext>
-#include <QOpenGLFunctions>
-#include <QOpenGLFramebufferObject>
-#include <QOpenGLShaderProgram>
-#include <QOpenGLVertexArrayObject>
-#include <QOpenGLBuffer>
-#include <QOpenGLVertexArrayObject>
-#include <QOffscreenSurface>
-#include <QQmlEngine>
-#include <QQmlComponent>
-#include <QQuickItem>
-#include <QQuickWindow>
-#include <QQuickRenderControl>
-#include <QCoreApplication>
-
-/*
-  This implementation runs the Qt Quick scenegraph's sync and render phases on a
-  separate, dedicated thread.  Rendering the cube using our custom OpenGL engine
-  happens on that thread as well.  This is similar to the built-in threaded
-  render loop, but does not support all the features. There is no support for
-  getting Animators running on the render thread for example.
-
-  We choose to use QObject's event mechanism to communicate with the QObject
-  living on the render thread. An alternative would be to subclass QThread and
-  reimplement run() with a custom event handling approach, like
-  QSGThreadedRenderLoop does. That would potentially lead to better results but
-  is also more complex.
-*/
-
-static const QEvent::Type INIT = QEvent::Type(QEvent::User + 1);
-static const QEvent::Type RENDER = QEvent::Type(QEvent::User + 2);
-static const QEvent::Type RESIZE = QEvent::Type(QEvent::User + 3);
-static const QEvent::Type STOP = QEvent::Type(QEvent::User + 4);
-
-static const QEvent::Type UPDATE = QEvent::Type(QEvent::User + 5);
-
-QuickRenderer::QuickRenderer()
-    : m_context(nullptr),
-      m_surface(nullptr),
-      m_fbo(nullptr),
-      m_window(nullptr),
-      m_quickWindow(nullptr),
-      m_renderControl(nullptr),
-      m_cubeRenderer(nullptr),
-      m_quit(false)
-{
-}
-
-void QuickRenderer::requestInit()
-{
-    QCoreApplication::postEvent(this, new QEvent(INIT));
-}
-
-void QuickRenderer::requestRender()
-{
-    QCoreApplication::postEvent(this, new QEvent(RENDER));
-}
-
-void QuickRenderer::requestResize()
-{
-    QCoreApplication::postEvent(this, new QEvent(RESIZE));
-}
-
-void QuickRenderer::requestStop()
-{
-    QCoreApplication::postEvent(this, new QEvent(STOP));
-}
-
-bool QuickRenderer::event(QEvent *e)
-{
-    QMutexLocker lock(&m_mutex);
-
-    switch (int(e->type())) {
-    case INIT:
-        init();
-        return true;
-    case RENDER:
-        render(&lock);
-        return true;
-    case RESIZE:
-        if (m_cubeRenderer)
-            m_cubeRenderer->resize(m_window->width(), m_window->height());
-        return true;
-    case STOP:
-        cleanup();
-        return true;
-    default:
-        return QObject::event(e);
-    }
-}
-
-void QuickRenderer::init()
-{
-    m_context->makeCurrent(m_surface);
-
-    // Pass our offscreen surface to the cube renderer just so that it will
-    // have something is can make current during cleanup. QOffscreenSurface,
-    // just like QWindow, must always be created on the gui thread (as it might
-    // be backed by an actual QWindow).
-    m_cubeRenderer = new CubeRenderer(m_surface);
-    m_cubeRenderer->resize(m_window->width(), m_window->height());
-
-    m_renderControl->initialize(m_context);
-}
-
-void QuickRenderer::cleanup()
-{
-    m_context->makeCurrent(m_surface);
-
-    m_renderControl->invalidate();
-
-    delete m_fbo;
-    m_fbo = nullptr;
-
-    delete m_cubeRenderer;
-    m_cubeRenderer = nullptr;
-
-    m_context->doneCurrent();
-    m_context->moveToThread(QCoreApplication::instance()->thread());
-
-    m_cond.wakeOne();
-}
-
-void QuickRenderer::ensureFbo()
-{
-    if (m_fbo && m_fbo->size() != m_window->size() * m_window->devicePixelRatio()) {
-        delete m_fbo;
-        m_fbo = nullptr;
-    }
-
-    if (!m_fbo) {
-        m_fbo = new QOpenGLFramebufferObject(m_window->size() * m_window->devicePixelRatio(),
-                                             QOpenGLFramebufferObject::CombinedDepthStencil);
-        m_quickWindow->setRenderTarget(m_fbo);
-    }
-}
-
-void QuickRenderer::render(QMutexLocker *lock)
-{
-    Q_ASSERT(QThread::currentThread() != m_window->thread());
-
-    if (!m_context->makeCurrent(m_surface)) {
-        qWarning("Failed to make context current on render thread");
-        return;
-    }
-
-    ensureFbo();
-
-    // Synchronization and rendering happens here on the render thread.
-    m_renderControl->sync();
-
-    // The gui thread can now continue.
-    m_cond.wakeOne();
-    lock->unlock();
-
-    // Meanwhile on this thread continue with the actual rendering (into the FBO first).
-    m_renderControl->render();
-    m_context->functions()->glFlush();
-
-    // The cube renderer uses its own context, no need to bother with the state here.
-
-    // Get something onto the screen using our custom OpenGL engine.
-    QMutexLocker quitLock(&m_quitMutex);
-    if (!m_quit)
-        m_cubeRenderer->render(m_window, m_context, m_fbo->texture());
-}
-
-void QuickRenderer::aboutToQuit()
-{
-    QMutexLocker lock(&m_quitMutex);
-    m_quit = true;
-}
-
-class RenderControl : public QQuickRenderControl
-{
-public:
-    RenderControl(QWindow *w) : m_window(w) { }
-    QWindow *renderWindow(QPoint *offset) override;
-
-private:
-    QWindow *m_window;
-};
-
-WindowMultiThreaded::WindowMultiThreaded()
-    : m_qmlComponent(nullptr),
-      m_rootItem(nullptr),
-      m_quickInitialized(false),
-      m_psrRequested(false)
-{
-    setSurfaceType(QSurface::OpenGLSurface);
-
-    QSurfaceFormat format;
-    // Qt Quick may need a depth and stencil buffer. Always make sure these are available.
-    format.setDepthBufferSize(16);
-    format.setStencilBufferSize(8);
-    setFormat(format);
-
-    m_context = new QOpenGLContext;
-    m_context->setFormat(format);
-    m_context->create();
-
-    m_offscreenSurface = new QOffscreenSurface;
-    // Pass m_context->format(), not format. Format does not specify and color buffer
-    // sizes, while the context, that has just been created, reports a format that has
-    // these values filled in. Pass this to the offscreen surface to make sure it will be
-    // compatible with the context's configuration.
-    m_offscreenSurface->setFormat(m_context->format());
-    m_offscreenSurface->create();
-
-    m_renderControl = new RenderControl(this);
-
-    // Create a QQuickWindow that is associated with out render control. Note that this
-    // window never gets created or shown, meaning that it will never get an underlying
-    // native (platform) window.
-    m_quickWindow = new QQuickWindow(m_renderControl);
-
-    // Create a QML engine.
-    m_qmlEngine = new QQmlEngine;
-    if (!m_qmlEngine->incubationController())
-        m_qmlEngine->setIncubationController(m_quickWindow->incubationController());
-
-    m_quickRenderer = new QuickRenderer;
-    m_quickRenderer->setContext(m_context);
-
-    // These live on the gui thread. Just give access to them on the render thread.
-    m_quickRenderer->setSurface(m_offscreenSurface);
-    m_quickRenderer->setWindow(this);
-    m_quickRenderer->setQuickWindow(m_quickWindow);
-    m_quickRenderer->setRenderControl(m_renderControl);
-
-    m_quickRendererThread = new QThread;
-
-    // Notify the render control that some scenegraph internals have to live on
-    // m_quickRenderThread.
-    m_renderControl->prepareThread(m_quickRendererThread);
-
-    // The QOpenGLContext and the QObject representing the rendering logic on
-    // the render thread must live on that thread.
-    m_context->moveToThread(m_quickRendererThread);
-    m_quickRenderer->moveToThread(m_quickRendererThread);
-
-    m_quickRendererThread->start();
-
-    // Now hook up the signals. For simplicy we don't differentiate
-    // between renderRequested (only render is needed, no sync) and
-    // sceneChanged (polish and sync is needed too).
-    connect(m_renderControl, &QQuickRenderControl::renderRequested, this, &WindowMultiThreaded::requestUpdate);
-    connect(m_renderControl, &QQuickRenderControl::sceneChanged, this, &WindowMultiThreaded::requestUpdate);
-}
-
-WindowMultiThreaded::~WindowMultiThreaded()
-{
-    // Release resources and move the context ownership back to this thread.
-    m_quickRenderer->mutex()->lock();
-    m_quickRenderer->requestStop();
-    m_quickRenderer->cond()->wait(m_quickRenderer->mutex());
-    m_quickRenderer->mutex()->unlock();
-
-    m_quickRendererThread->quit();
-    m_quickRendererThread->wait();
-
-    delete m_renderControl;
-    delete m_qmlComponent;
-    delete m_quickWindow;
-    delete m_qmlEngine;
-
-    delete m_offscreenSurface;
-    delete m_context;
-}
-
-void WindowMultiThreaded::requestUpdate()
-{
-    if (m_quickInitialized && !m_psrRequested) {
-        m_psrRequested = true;
-        QCoreApplication::postEvent(this, new QEvent(UPDATE));
-    }
-}
-
-bool WindowMultiThreaded::event(QEvent *e)
-{
-    if (e->type() == UPDATE) {
-        polishSyncAndRender();
-        m_psrRequested = false;
-        return true;
-    } else if (e->type() == QEvent::Close) {
-        // Avoid rendering on the render thread when the window is about to
-        // close. Once a QWindow is closed, the underlying platform window will
-        // go away, even though the QWindow instance itself is still
-        // valid. Operations like swapBuffers() are futile and only result in
-        // warnings afterwards. Prevent this.
-        m_quickRenderer->aboutToQuit();
-    }
-    return QWindow::event(e);
-}
-
-void WindowMultiThreaded::polishSyncAndRender()
-{
-    Q_ASSERT(QThread::currentThread() == thread());
-
-    // Polishing happens on the gui thread.
-    m_renderControl->polishItems();
-    // Sync happens on the render thread with the gui thread (this one) blocked.
-    QMutexLocker lock(m_quickRenderer->mutex());
-    m_quickRenderer->requestRender();
-    // Wait until sync is complete.
-    m_quickRenderer->cond()->wait(m_quickRenderer->mutex());
-    // Rendering happens on the render thread without blocking the gui (main)
-    // thread. This is good because the blocking swap (waiting for vsync)
-    // happens on the render thread, not blocking other work.
-}
-
-void WindowMultiThreaded::run()
-{
-    disconnect(m_qmlComponent, &QQmlComponent::statusChanged, this, &WindowMultiThreaded::run);
-
-    if (m_qmlComponent->isError()) {
-        const QList<QQmlError> errorList = m_qmlComponent->errors();
-        for (const QQmlError &error : errorList)
-            qWarning() << error.url() << error.line() << error;
-        return;
-    }
-
-    QObject *rootObject = m_qmlComponent->create();
-    if (m_qmlComponent->isError()) {
-        const QList<QQmlError> errorList = m_qmlComponent->errors();
-        for (const QQmlError &error : errorList)
-            qWarning() << error.url() << error.line() << error;
-        return;
-    }
-
-    m_rootItem = qobject_cast<QQuickItem *>(rootObject);
-    if (!m_rootItem) {
-        qWarning("run: Not a QQuickItem");
-        delete rootObject;
-        return;
-    }
-
-    // The root item is ready. Associate it with the window.
-    m_rootItem->setParentItem(m_quickWindow->contentItem());
-
-    // Update item and rendering related geometries.
-    updateSizes();
-
-    m_quickInitialized = true;
-
-    // Initialize the render thread and perform the first polish/sync/render.
-    m_quickRenderer->requestInit();
-    polishSyncAndRender();
-}
-
-void WindowMultiThreaded::updateSizes()
-{
-    // Behave like SizeRootObjectToView.
-    m_rootItem->setWidth(width());
-    m_rootItem->setHeight(height());
-
-    m_quickWindow->setGeometry(0, 0, width(), height());
-}
-
-void WindowMultiThreaded::startQuick(const QString &filename)
-{
-    m_qmlComponent = new QQmlComponent(m_qmlEngine, QUrl(filename));
-    if (m_qmlComponent->isLoading())
-        connect(m_qmlComponent, &QQmlComponent::statusChanged, this, &WindowMultiThreaded::run);
-    else
-        run();
-}
-
-void WindowMultiThreaded::exposeEvent(QExposeEvent *)
-{
-    if (isExposed()) {
-        if (!m_quickInitialized)
-            startQuick(QStringLiteral("qrc:/rendercontrol/demo.qml"));
-    }
-}
-
-void WindowMultiThreaded::resizeEvent(QResizeEvent *)
-{
-    // If this is a resize after the scene is up and running, recreate the fbo and the
-    // Quick item and scene.
-    if (m_rootItem) {
-        updateSizes();
-        m_quickRenderer->requestResize();
-        polishSyncAndRender();
-    }
-}
-
-void WindowMultiThreaded::mousePressEvent(QMouseEvent *e)
-{
-    // Use the constructor taking localPos and screenPos. That puts localPos into the
-    // event's localPos and windowPos, and screenPos into the event's screenPos. This way
-    // the windowPos in e is ignored and is replaced by localPos. This is necessary
-    // because QQuickWindow thinks of itself as a top-level window always.
-    QMouseEvent mappedEvent(e->type(), e->localPos(), e->screenPos(), e->button(), e->buttons(), e->modifiers());
-    QCoreApplication::sendEvent(m_quickWindow, &mappedEvent);
-}
-
-void WindowMultiThreaded::mouseReleaseEvent(QMouseEvent *e)
-{
-    QMouseEvent mappedEvent(e->type(), e->localPos(), e->screenPos(), e->button(), e->buttons(), e->modifiers());
-    QCoreApplication::sendEvent(m_quickWindow, &mappedEvent);
-}
diff --git a/examples/quick/rendercontrol/rendercontrol_opengl/window_multithreaded.h b/examples/quick/rendercontrol/rendercontrol_opengl/window_multithreaded.h
deleted file mode 100644
index ded80a0064..0000000000
--- a/examples/quick/rendercontrol/rendercontrol_opengl/window_multithreaded.h
+++ /dev/null
@@ -1,152 +0,0 @@
-/****************************************************************************
-**
-** Copyright (C) 2017 The Qt Company Ltd.
-** Contact: https://www.qt.io/licensing/
-**
-** This file is part of the examples of the Qt Toolkit.
-**
-** $QT_BEGIN_LICENSE:BSD$
-** Commercial License Usage
-** Licensees holding valid commercial Qt licenses may use this file in
-** accordance with the commercial license agreement provided with the
-** Software or, alternatively, in accordance with the terms contained in
-** a written agreement between you and The Qt Company. For licensing terms
-** and conditions see https://www.qt.io/terms-conditions. For further
-** information use the contact form at https://www.qt.io/contact-us.
-**
-** BSD License Usage
-** Alternatively, you may use this file under the terms of the BSD license
-** as follows:
-**
-** "Redistribution and use in source and binary forms, with or without
-** modification, are permitted provided that the following conditions are
-** met:
-**   * Redistributions of source code must retain the above copyright
-**     notice, this list of conditions and the following disclaimer.
-**   * Redistributions in binary form must reproduce the above copyright
-**     notice, this list of conditions and the following disclaimer in
-**     the documentation and/or other materials provided with the
-**     distribution.
-**   * Neither the name of The Qt Company Ltd nor the names of its
-**     contributors may be used to endorse or promote products derived
-**     from this software without specific prior written permission.
-**
-**
-** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
-** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
-** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
-** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
-** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
-** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
-** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
-** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
-** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
-** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
-** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
-**
-** $QT_END_LICENSE$
-**
-****************************************************************************/
-
-#ifndef WINDOW_MULTITHREADED_H
-#define WINDOW_MULTITHREADED_H
-
-#include <QWindow>
-#include <QMatrix4x4>
-#include <QThread>
-#include <QWaitCondition>
-#include <QMutex>
-
-QT_FORWARD_DECLARE_CLASS(QOpenGLContext)
-QT_FORWARD_DECLARE_CLASS(QOpenGLFramebufferObject)
-QT_FORWARD_DECLARE_CLASS(QOffscreenSurface)
-QT_FORWARD_DECLARE_CLASS(QQuickRenderControl)
-QT_FORWARD_DECLARE_CLASS(QQuickWindow)
-QT_FORWARD_DECLARE_CLASS(QQmlEngine)
-QT_FORWARD_DECLARE_CLASS(QQmlComponent)
-QT_FORWARD_DECLARE_CLASS(QQuickItem)
-
-class CubeRenderer;
-
-class QuickRenderer : public QObject
-{
-    Q_OBJECT
-
-public:
-    QuickRenderer();
-
-    void requestInit();
-    void requestRender();
-    void requestResize();
-    void requestStop();
-
-    QWaitCondition *cond() { return &m_cond; }
-    QMutex *mutex() { return &m_mutex; }
-
-    void setContext(QOpenGLContext *ctx) { m_context = ctx; }
-    void setSurface(QOffscreenSurface *s) { m_surface = s; }
-    void setWindow(QWindow *w) { m_window = w; }
-    void setQuickWindow(QQuickWindow *w) { m_quickWindow = w; }
-    void setRenderControl(QQuickRenderControl *r) { m_renderControl = r; }
-
-    void aboutToQuit();
-
-private:
-    bool event(QEvent *e) override;
-    void init();
-    void cleanup();
-    void ensureFbo();
-    void render(QMutexLocker *lock);
-
-    QWaitCondition m_cond;
-    QMutex m_mutex;
-    QOpenGLContext *m_context;
-    QOffscreenSurface *m_surface;
-    QOpenGLFramebufferObject *m_fbo;
-    QWindow *m_window;
-    QQuickWindow *m_quickWindow;
-    QQuickRenderControl *m_renderControl;
-    CubeRenderer *m_cubeRenderer;
-    QMutex m_quitMutex;
-    bool m_quit;
-};
-
-class WindowMultiThreaded : public QWindow
-{
-    Q_OBJECT
-
-public:
-    WindowMultiThreaded();
-    ~WindowMultiThreaded();
-
-protected:
-    void exposeEvent(QExposeEvent *e) override;
-    void resizeEvent(QResizeEvent *e) override;
-    void mousePressEvent(QMouseEvent *e) override;
-    void mouseReleaseEvent(QMouseEvent *e) override;
-    bool event(QEvent *e) override;
-
-private slots:
-    void run();
-    void requestUpdate();
-    void polishSyncAndRender();
-
-private:
-    void startQuick(const QString &filename);
-    void updateSizes();
-
-    QuickRenderer *m_quickRenderer;
-    QThread *m_quickRendererThread;
-
-    QOpenGLContext *m_context;
-    QOffscreenSurface *m_offscreenSurface;
-    QQuickRenderControl *m_renderControl;
-    QQuickWindow *m_quickWindow;
-    QQmlEngine *m_qmlEngine;
-    QQmlComponent *m_qmlComponent;
-    QQuickItem *m_rootItem;
-    bool m_quickInitialized;
-    bool m_psrRequested;
-};
-
-#endif
diff --git a/examples/quick/rendercontrol/rendercontrol_opengl/window_singlethreaded.cpp b/examples/quick/rendercontrol/rendercontrol_opengl/window_singlethreaded.cpp
index ddbbfe4b52..fb3c0b4f4f 100644
--- a/examples/quick/rendercontrol/rendercontrol_opengl/window_singlethreaded.cpp
+++ b/examples/quick/rendercontrol/rendercontrol_opengl/window_singlethreaded.cpp
@@ -56,7 +56,6 @@
 #include <QOpenGLShaderProgram>
 #include <QOpenGLVertexArrayObject>
 #include <QOpenGLBuffer>
-#include <QOpenGLVertexArrayObject>
 #include <QOffscreenSurface>
 #include <QScreen>
 #include <QQmlEngine>
@@ -65,6 +64,8 @@
 #include <QQuickWindow>
 #include <QQuickRenderControl>
 #include <QCoreApplication>
+#include <QQuickRenderTarget>
+#include <QQuickGraphicsDevice>
 
 class RenderControl : public QQuickRenderControl
 {
@@ -85,17 +86,13 @@ QWindow *RenderControl::renderWindow(QPoint *offset)
 
 WindowSingleThreaded::WindowSingleThreaded()
     : m_rootItem(nullptr),
-      m_fbo(nullptr),
+      m_textureId(0),
       m_quickInitialized(false),
       m_quickReady(false),
       m_dpr(0)
 {
     setSurfaceType(QSurface::OpenGLSurface);
 
-    // The rendercontrol does not necessarily need an FBO. Demonstrate this
-    // when requested.
-    m_onscreen = QCoreApplication::arguments().contains(QStringLiteral("--onscreen"));
-
     QSurfaceFormat format;
     // Qt Quick may need a depth and stencil buffer. Always make sure these are available.
     format.setDepthBufferSize(16);
@@ -137,13 +134,13 @@ WindowSingleThreaded::WindowSingleThreaded()
     // Now hook up the signals. For simplicy we don't differentiate between
     // renderRequested (only render is needed, no sync) and sceneChanged (polish and sync
     // is needed too).
-    connect(m_quickWindow, &QQuickWindow::sceneGraphInitialized, this, &WindowSingleThreaded::createFbo);
-    connect(m_quickWindow, &QQuickWindow::sceneGraphInvalidated, this, &WindowSingleThreaded::destroyFbo);
+    connect(m_quickWindow, &QQuickWindow::sceneGraphInitialized, this, &WindowSingleThreaded::createTexture);
+    connect(m_quickWindow, &QQuickWindow::sceneGraphInvalidated, this, &WindowSingleThreaded::destroyTexture);
     connect(m_renderControl, &QQuickRenderControl::renderRequested, this, &WindowSingleThreaded::requestUpdate);
     connect(m_renderControl, &QQuickRenderControl::sceneChanged, this, &WindowSingleThreaded::requestUpdate);
 
-    // Just recreating the FBO on resize is not sufficient, when moving between screens
-    // with different devicePixelRatio the QWindow size may remain the same but the FBO
+    // Just recreating the texture on resize is not sufficient, when moving between screens
+    // with different devicePixelRatio the QWindow size may remain the same but the texture
     // dimension is to change regardless.
     connect(this, &QWindow::screenChanged, this, &WindowSingleThreaded::handleScreenChange);
 }
@@ -156,14 +153,13 @@ WindowSingleThreaded::~WindowSingleThreaded()
     // another surface that is valid for sure.
     m_context->makeCurrent(m_offscreenSurface);
 
-    // Delete the render control first since it will free the scenegraph resources.
-    // Destroy the QQuickWindow only afterwards.
-    delete m_renderControl;
-
     delete m_qmlComponent;
-    delete m_quickWindow;
     delete m_qmlEngine;
-    delete m_fbo;
+    delete m_quickWindow;
+    delete m_renderControl;
+
+    if (m_textureId)
+        m_context->functions()->glDeleteTextures(1, &m_textureId);
 
     m_context->doneCurrent();
 
@@ -173,42 +169,42 @@ WindowSingleThreaded::~WindowSingleThreaded()
     delete m_context;
 }
 
-void WindowSingleThreaded::createFbo()
+void WindowSingleThreaded::createTexture()
 {
-    // The scene graph has been initialized. It is now time to create an FBO and associate
+    // The scene graph has been initialized. It is now time to create an texture and associate
     // it with the QQuickWindow.
     m_dpr = devicePixelRatio();
-    if (!m_onscreen) {
-        m_fbo = new QOpenGLFramebufferObject(size() * m_dpr, QOpenGLFramebufferObject::CombinedDepthStencil);
-        m_quickWindow->setRenderTarget(m_fbo);
-    } else {
-        // Special case: No FBO. Render directly to the window's default framebuffer.
-        m_onscreenSize = size() * m_dpr;
-        m_quickWindow->setRenderTarget(0, m_onscreenSize);
-    }
+    m_textureSize = size() * m_dpr;
+    QOpenGLFunctions *f = m_context->functions();
+    f->glGenTextures(1, &m_textureId);
+    f->glBindTexture(GL_TEXTURE_2D, m_textureId);
+    f->glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
+    f->glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
+    f->glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, m_textureSize.width(), m_textureSize.height(), 0,
+                    GL_RGBA, GL_UNSIGNED_BYTE, nullptr);
+    m_quickWindow->setRenderTarget(QQuickRenderTarget::fromNativeTexture({ &m_textureId, 0 }, m_textureSize));
 }
 
-void WindowSingleThreaded::destroyFbo()
+void WindowSingleThreaded::destroyTexture()
 {
-    delete m_fbo;
-    m_fbo = nullptr;
+    m_context->functions()->glDeleteTextures(1, &m_textureId);
+    m_textureId = 0;
 }
 
 void WindowSingleThreaded::render()
 {
-    QSurface *surface = m_offscreenSurface;
-    if (m_onscreen)
-        surface = this;
-    if (!m_context->makeCurrent(surface))
+    if (!m_context->makeCurrent(m_offscreenSurface))
         return;
 
-    // Polish, synchronize and render the next frame (into our fbo).  In this example
+    // Polish, synchronize and render the next frame (into our texture).  In this example
     // everything happens on the same thread and therefore all three steps are performed
     // in succession from here. In a threaded setup the render() call would happen on a
     // separate thread.
+    m_renderControl->beginFrame();
     m_renderControl->polishItems();
     m_renderControl->sync();
     m_renderControl->render();
+    m_renderControl->endFrame();
 
     m_quickWindow->resetOpenGLState();
     QOpenGLFramebufferObject::bindDefault();
@@ -218,10 +214,7 @@ void WindowSingleThreaded::render()
     m_quickReady = true;
 
     // Get something onto the screen.
-    if (!m_onscreen)
-        m_cubeRenderer->render(this, m_context, m_quickReady ? m_fbo->texture() : 0);
-    else
-        m_context->swapBuffers(this);
+    m_cubeRenderer->render(this, m_context, m_quickReady ? m_textureId : 0);
 }
 
 void WindowSingleThreaded::requestUpdate()
@@ -263,11 +256,9 @@ void WindowSingleThreaded::run()
     updateSizes();
 
     // Initialize the render control and our OpenGL resources.
-    QSurface *surface = m_offscreenSurface;
-    if (m_onscreen)
-        surface = this;
-    m_context->makeCurrent(surface);
-    m_renderControl->initialize(m_context);
+    m_context->makeCurrent(m_offscreenSurface);
+    m_quickWindow->setGraphicsDevice(QQuickGraphicsDevice::fromOpenGLContext(m_context));
+    m_renderControl->initialize();
     m_quickInitialized = true;
 }
 
@@ -295,21 +286,18 @@ void WindowSingleThreaded::exposeEvent(QExposeEvent *)
 {
     if (isExposed()) {
         if (!m_quickInitialized) {
-            if (!m_onscreen)
-                m_cubeRenderer->render(this, m_context, m_quickReady ? m_fbo->texture() : 0);
+            m_cubeRenderer->render(this, m_context, m_quickReady ? m_textureId : 0);
             startQuick(QStringLiteral("qrc:/rendercontrol/demo.qml"));
         }
     }
 }
 
-void WindowSingleThreaded::resizeFbo()
+void WindowSingleThreaded::resizeTexture()
 {
-    QSurface *surface = m_offscreenSurface;
-    if (m_onscreen)
-        surface = this;
-    if (m_rootItem && m_context->makeCurrent(surface)) {
-        delete m_fbo;
-        createFbo();
+    if (m_rootItem && m_context->makeCurrent(m_offscreenSurface)) {
+        m_context->functions()->glDeleteTextures(1, &m_textureId);
+        m_textureId = 0;
+        createTexture();
         m_context->doneCurrent();
         updateSizes();
         render();
@@ -318,21 +306,16 @@ void WindowSingleThreaded::resizeFbo()
 
 void WindowSingleThreaded::resizeEvent(QResizeEvent *)
 {
-    // If this is a resize after the scene is up and running, recreate the fbo and the
+    // If this is a resize after the scene is up and running, recreate the texture and the
     // Quick item and scene.
-    if (!m_onscreen) {
-        if (m_fbo && m_fbo->size() != size() * devicePixelRatio())
-            resizeFbo();
-    } else {
-        if (m_onscreenSize != size() * devicePixelRatio())
-            resizeFbo();
-    }
+    if (m_textureId && m_textureSize != size() * devicePixelRatio())
+        resizeTexture();
 }
 
 void WindowSingleThreaded::handleScreenChange()
 {
     if (m_dpr != devicePixelRatio())
-        resizeFbo();
+        resizeTexture();
 }
 
 void WindowSingleThreaded::mousePressEvent(QMouseEvent *e)
diff --git a/examples/quick/rendercontrol/rendercontrol_opengl/window_singlethreaded.h b/examples/quick/rendercontrol/rendercontrol_opengl/window_singlethreaded.h
index 44b79d9f51..ad53d5c8a5 100644
--- a/examples/quick/rendercontrol/rendercontrol_opengl/window_singlethreaded.h
+++ b/examples/quick/rendercontrol/rendercontrol_opengl/window_singlethreaded.h
@@ -55,14 +55,16 @@
 #include <QMatrix4x4>
 #include <QTimer>
 
-QT_FORWARD_DECLARE_CLASS(QOpenGLContext)
-QT_FORWARD_DECLARE_CLASS(QOpenGLFramebufferObject)
-QT_FORWARD_DECLARE_CLASS(QOffscreenSurface)
-QT_FORWARD_DECLARE_CLASS(QQuickRenderControl)
-QT_FORWARD_DECLARE_CLASS(QQuickWindow)
-QT_FORWARD_DECLARE_CLASS(QQmlEngine)
-QT_FORWARD_DECLARE_CLASS(QQmlComponent)
-QT_FORWARD_DECLARE_CLASS(QQuickItem)
+QT_BEGIN_NAMESPACE
+class QOpenGLContext;
+class QOpenGLTexture;
+class QOffscreenSurface;
+class QQuickRenderControl;
+class QQuickWindow;
+class QQmlEngine;
+class QQmlComponent;
+class QQuickItem;
+QT_END_NAMESPACE
 
 class CubeRenderer;
 
@@ -83,8 +85,8 @@ protected:
 private slots:
     void run();
 
-    void createFbo();
-    void destroyFbo();
+    void createTexture();
+    void destroyTexture();
     void render();
     void requestUpdate();
     void handleScreenChange();
@@ -92,7 +94,7 @@ private slots:
 private:
     void startQuick(const QString &filename);
     void updateSizes();
-    void resizeFbo();
+    void resizeTexture();
 
     QOpenGLContext *m_context;
     QOffscreenSurface *m_offscreenSurface;
@@ -101,14 +103,13 @@ private:
     QQmlEngine *m_qmlEngine;
     QQmlComponent *m_qmlComponent;
     QQuickItem *m_rootItem;
-    QOpenGLFramebufferObject *m_fbo;
+    uint m_textureId;
+    QSize m_textureSize;
     bool m_quickInitialized;
     bool m_quickReady;
     QTimer m_updateTimer;
     CubeRenderer *m_cubeRenderer;
     qreal m_dpr;
-    bool m_onscreen;
-    QSize m_onscreenSize;
 };
 
 #endif