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<h1 class="title">threadrenderer.cpp Example File</h1>
<span class="subtitle">scenegraph/textureinthread/threadrenderer.cpp</span>
<!-- $$$scenegraph/textureinthread/threadrenderer.cpp-description -->
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<pre class="cpp"><span class="comment">/****************************************************************************
**
** Copyright (C) 2015 The Qt Company Ltd.
** Contact: http://www.qt.io/licensing/
**
** This file is part of the examples of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:BSD$
** You may use this file under the terms of the BSD license as follows:
**
** &quot;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
** &quot;AS IS&quot; 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.&quot;
**
** $QT_END_LICENSE$
**
****************************************************************************/</span>

<span class="preprocessor">#include &quot;threadrenderer.h&quot;</span>
<span class="preprocessor">#include &quot;logorenderer.h&quot;</span>

<span class="preprocessor">#include &lt;QtCore/QMutex&gt;</span>
<span class="preprocessor">#include &lt;QtCore/QThread&gt;</span>

<span class="preprocessor">#include &lt;QtGui/QOpenGLContext&gt;</span>
<span class="preprocessor">#include &lt;QtGui/QOpenGLFramebufferObject&gt;</span>
<span class="preprocessor">#include &lt;QtGui/QGuiApplication&gt;</span>
<span class="preprocessor">#include &lt;QtGui/QOffscreenSurface&gt;</span>

<span class="preprocessor">#include &lt;QtQuick/QQuickWindow&gt;</span>
<span class="preprocessor">#include &lt;qsgsimpletexturenode.h&gt;</span>

<span class="type">QList</span><span class="operator">&lt;</span><span class="type">QThread</span> <span class="operator">*</span><span class="operator">&gt;</span> ThreadRenderer<span class="operator">::</span>threads;

<span class="comment">/*
 * The render thread shares a context with the scene graph and will
 * render into two separate FBOs, one to use for display and one
 * to use for rendering
 */</span>
<span class="keyword">class</span> RenderThread : <span class="keyword">public</span> <span class="type">QThread</span>
{
    Q_OBJECT
<span class="keyword">public</span>:
    RenderThread(<span class="keyword">const</span> <span class="type">QSize</span> <span class="operator">&amp;</span>size)
        : surface(<span class="number">0</span>)
        <span class="operator">,</span> context(<span class="number">0</span>)
        <span class="operator">,</span> m_renderFbo(<span class="number">0</span>)
        <span class="operator">,</span> m_displayFbo(<span class="number">0</span>)
        <span class="operator">,</span> m_logoRenderer(<span class="number">0</span>)
        <span class="operator">,</span> m_size(size)
    {
        ThreadRenderer<span class="operator">::</span>threads <span class="operator">&lt;</span><span class="operator">&lt;</span> <span class="keyword">this</span>;
    }

    <span class="type">QOffscreenSurface</span> <span class="operator">*</span>surface;
    <span class="type">QOpenGLContext</span> <span class="operator">*</span>context;

<span class="keyword">public</span> <span class="keyword">slots</span>:
    <span class="type">void</span> renderNext()
    {
        context<span class="operator">-</span><span class="operator">&gt;</span>makeCurrent(surface);

        <span class="keyword">if</span> (<span class="operator">!</span>m_renderFbo) {
            <span class="comment">// Initialize the buffers and renderer</span>
            <span class="type">QOpenGLFramebufferObjectFormat</span> format;
            format<span class="operator">.</span>setAttachment(<span class="type">QOpenGLFramebufferObject</span><span class="operator">::</span>CombinedDepthStencil);
            m_renderFbo <span class="operator">=</span> <span class="keyword">new</span> <span class="type">QOpenGLFramebufferObject</span>(m_size<span class="operator">,</span> format);
            m_displayFbo <span class="operator">=</span> <span class="keyword">new</span> <span class="type">QOpenGLFramebufferObject</span>(m_size<span class="operator">,</span> format);
            m_logoRenderer <span class="operator">=</span> <span class="keyword">new</span> LogoRenderer();
            m_logoRenderer<span class="operator">-</span><span class="operator">&gt;</span>initialize();
        }

        m_renderFbo<span class="operator">-</span><span class="operator">&gt;</span>bind();
        context<span class="operator">-</span><span class="operator">&gt;</span>functions()<span class="operator">-</span><span class="operator">&gt;</span>glViewport(<span class="number">0</span><span class="operator">,</span> <span class="number">0</span><span class="operator">,</span> m_size<span class="operator">.</span>width()<span class="operator">,</span> m_size<span class="operator">.</span>height());

        m_logoRenderer<span class="operator">-</span><span class="operator">&gt;</span>render();

        <span class="comment">// We need to flush the contents to the FBO before posting</span>
        <span class="comment">// the texture to the other thread, otherwise, we might</span>
        <span class="comment">// get unexpected results.</span>
        context<span class="operator">-</span><span class="operator">&gt;</span>functions()<span class="operator">-</span><span class="operator">&gt;</span>glFlush();

        m_renderFbo<span class="operator">-</span><span class="operator">&gt;</span>bindDefault();
        qSwap(m_renderFbo<span class="operator">,</span> m_displayFbo);

        <span class="keyword">emit</span> textureReady(m_displayFbo<span class="operator">-</span><span class="operator">&gt;</span>texture()<span class="operator">,</span> m_size);
    }

    <span class="type">void</span> shutDown()
    {
        context<span class="operator">-</span><span class="operator">&gt;</span>makeCurrent(surface);
        <span class="keyword">delete</span> m_renderFbo;
        <span class="keyword">delete</span> m_displayFbo;
        <span class="keyword">delete</span> m_logoRenderer;
        context<span class="operator">-</span><span class="operator">&gt;</span>doneCurrent();
        <span class="keyword">delete</span> context;

        <span class="comment">// schedule this to be deleted only after we're done cleaning up</span>
        surface<span class="operator">-</span><span class="operator">&gt;</span>deleteLater();

        <span class="comment">// Stop event processing, move the thread to GUI and make sure it is deleted.</span>
        exit();
        moveToThread(<span class="type">QGuiApplication</span><span class="operator">::</span>instance()<span class="operator">-</span><span class="operator">&gt;</span>thread());
    }

<span class="keyword">signals</span>:
    <span class="type">void</span> textureReady(<span class="type">int</span> id<span class="operator">,</span> <span class="keyword">const</span> <span class="type">QSize</span> <span class="operator">&amp;</span>size);

<span class="keyword">private</span>:
    <span class="type">QOpenGLFramebufferObject</span> <span class="operator">*</span>m_renderFbo;
    <span class="type">QOpenGLFramebufferObject</span> <span class="operator">*</span>m_displayFbo;

    LogoRenderer <span class="operator">*</span>m_logoRenderer;
    <span class="type">QSize</span> m_size;
};

<span class="keyword">class</span> TextureNode : <span class="keyword">public</span> <span class="type">QObject</span><span class="operator">,</span> <span class="keyword">public</span> <span class="type"><a href="qsgsimpletexturenode.html">QSGSimpleTextureNode</a></span>
{
    Q_OBJECT

<span class="keyword">public</span>:
    TextureNode(<span class="type"><a href="qquickwindow.html">QQuickWindow</a></span> <span class="operator">*</span>window)
        : m_id(<span class="number">0</span>)
        <span class="operator">,</span> m_size(<span class="number">0</span><span class="operator">,</span> <span class="number">0</span>)
        <span class="operator">,</span> m_texture(<span class="number">0</span>)
        <span class="operator">,</span> m_window(window)
    {
        <span class="comment">// Our texture node must have a texture, so use the default 0 texture.</span>
        m_texture <span class="operator">=</span> m_window<span class="operator">-</span><span class="operator">&gt;</span>createTextureFromId(<span class="number">0</span><span class="operator">,</span> <span class="type">QSize</span>(<span class="number">1</span><span class="operator">,</span> <span class="number">1</span>));
        setTexture(m_texture);
        setFiltering(<span class="type"><a href="qsgtexture.html">QSGTexture</a></span><span class="operator">::</span>Linear);
    }

    <span class="operator">~</span>TextureNode()
    {
        <span class="keyword">delete</span> m_texture;
    }

<span class="keyword">signals</span>:
    <span class="type">void</span> textureInUse();
    <span class="type">void</span> pendingNewTexture();

<span class="keyword">public</span> <span class="keyword">slots</span>:

    <span class="comment">// This function gets called on the FBO rendering thread and will store the</span>
    <span class="comment">// texture id and size and schedule an update on the window.</span>
    <span class="type">void</span> newTexture(<span class="type">int</span> id<span class="operator">,</span> <span class="keyword">const</span> <span class="type">QSize</span> <span class="operator">&amp;</span>size) {
        m_mutex<span class="operator">.</span>lock();
        m_id <span class="operator">=</span> id;
        m_size <span class="operator">=</span> size;
        m_mutex<span class="operator">.</span>unlock();

        <span class="comment">// We cannot call QQuickWindow::update directly here, as this is only allowed</span>
        <span class="comment">// from the rendering thread or GUI thread.</span>
        <span class="keyword">emit</span> pendingNewTexture();
    }

    <span class="comment">// Before the scene graph starts to render, we update to the pending texture</span>
    <span class="type">void</span> prepareNode() {
        m_mutex<span class="operator">.</span>lock();
        <span class="type">int</span> newId <span class="operator">=</span> m_id;
        <span class="type">QSize</span> size <span class="operator">=</span> m_size;
        m_id <span class="operator">=</span> <span class="number">0</span>;
        m_mutex<span class="operator">.</span>unlock();
        <span class="keyword">if</span> (newId) {
            <span class="keyword">delete</span> m_texture;
            <span class="comment">// note: include QQuickWindow::TextureHasAlphaChannel if the rendered content</span>
            <span class="comment">// has alpha.</span>
            m_texture <span class="operator">=</span> m_window<span class="operator">-</span><span class="operator">&gt;</span>createTextureFromId(newId<span class="operator">,</span> size);
            setTexture(m_texture);

            markDirty(DirtyMaterial);

            <span class="comment">// This will notify the rendering thread that the texture is now being rendered</span>
            <span class="comment">// and it can start rendering to the other one.</span>
            <span class="keyword">emit</span> textureInUse();
        }
    }

<span class="keyword">private</span>:

    <span class="type">int</span> m_id;
    <span class="type">QSize</span> m_size;

    <span class="type">QMutex</span> m_mutex;

    <span class="type"><a href="qsgtexture.html">QSGTexture</a></span> <span class="operator">*</span>m_texture;
    <span class="type"><a href="qquickwindow.html">QQuickWindow</a></span> <span class="operator">*</span>m_window;
};

ThreadRenderer<span class="operator">::</span>ThreadRenderer()
    : m_renderThread(<span class="number">0</span>)
{
    setFlag(ItemHasContents<span class="operator">,</span> <span class="keyword">true</span>);
    m_renderThread <span class="operator">=</span> <span class="keyword">new</span> RenderThread(<span class="type">QSize</span>(<span class="number">512</span><span class="operator">,</span> <span class="number">512</span>));
}

<span class="type">void</span> ThreadRenderer<span class="operator">::</span>ready()
{
    m_renderThread<span class="operator">-</span><span class="operator">&gt;</span>surface <span class="operator">=</span> <span class="keyword">new</span> <span class="type">QOffscreenSurface</span>();
    m_renderThread<span class="operator">-</span><span class="operator">&gt;</span>surface<span class="operator">-</span><span class="operator">&gt;</span>setFormat(m_renderThread<span class="operator">-</span><span class="operator">&gt;</span>context<span class="operator">-</span><span class="operator">&gt;</span>format());
    m_renderThread<span class="operator">-</span><span class="operator">&gt;</span>surface<span class="operator">-</span><span class="operator">&gt;</span>create();

    m_renderThread<span class="operator">-</span><span class="operator">&gt;</span>moveToThread(m_renderThread);

    connect(window()<span class="operator">,</span> SIGNAL(sceneGraphInvalidated())<span class="operator">,</span> m_renderThread<span class="operator">,</span> SLOT(shutDown())<span class="operator">,</span> <span class="type">Qt</span><span class="operator">::</span>QueuedConnection);

    m_renderThread<span class="operator">-</span><span class="operator">&gt;</span>start();
    update();
}

<span class="type"><a href="qsgnode.html">QSGNode</a></span> <span class="operator">*</span>ThreadRenderer<span class="operator">::</span>updatePaintNode(<span class="type"><a href="qsgnode.html">QSGNode</a></span> <span class="operator">*</span>oldNode<span class="operator">,</span> UpdatePaintNodeData <span class="operator">*</span>)
{
    TextureNode <span class="operator">*</span>node <span class="operator">=</span> <span class="keyword">static_cast</span><span class="operator">&lt;</span>TextureNode <span class="operator">*</span><span class="operator">&gt;</span>(oldNode);

    <span class="keyword">if</span> (<span class="operator">!</span>m_renderThread<span class="operator">-</span><span class="operator">&gt;</span>context) {
        <span class="type">QOpenGLContext</span> <span class="operator">*</span>current <span class="operator">=</span> window()<span class="operator">-</span><span class="operator">&gt;</span>openglContext();
        <span class="comment">// Some GL implementations requres that the currently bound context is</span>
        <span class="comment">// made non-current before we set up sharing, so we doneCurrent here</span>
        <span class="comment">// and makeCurrent down below while setting up our own context.</span>
        current<span class="operator">-</span><span class="operator">&gt;</span>doneCurrent();

        m_renderThread<span class="operator">-</span><span class="operator">&gt;</span>context <span class="operator">=</span> <span class="keyword">new</span> <span class="type">QOpenGLContext</span>();
        m_renderThread<span class="operator">-</span><span class="operator">&gt;</span>context<span class="operator">-</span><span class="operator">&gt;</span>setFormat(current<span class="operator">-</span><span class="operator">&gt;</span>format());
        m_renderThread<span class="operator">-</span><span class="operator">&gt;</span>context<span class="operator">-</span><span class="operator">&gt;</span>setShareContext(current);
        m_renderThread<span class="operator">-</span><span class="operator">&gt;</span>context<span class="operator">-</span><span class="operator">&gt;</span>create();
        m_renderThread<span class="operator">-</span><span class="operator">&gt;</span>context<span class="operator">-</span><span class="operator">&gt;</span>moveToThread(m_renderThread);

        current<span class="operator">-</span><span class="operator">&gt;</span>makeCurrent(window());

        <span class="type">QMetaObject</span><span class="operator">::</span>invokeMethod(<span class="keyword">this</span><span class="operator">,</span> <span class="string">&quot;ready&quot;</span>);
        <span class="keyword">return</span> <span class="number">0</span>;
    }

    <span class="keyword">if</span> (<span class="operator">!</span>node) {
        node <span class="operator">=</span> <span class="keyword">new</span> TextureNode(window());

        <span class="comment">/* Set up connections to get the production of FBO textures in sync with vsync on the
         * rendering thread.
         *
         * When a new texture is ready on the rendering thread, we use a direct connection to
         * the texture node to let it know a new texture can be used. The node will then
         * emit pendingNewTexture which we bind to QQuickWindow::update to schedule a redraw.
         *
         * When the scene graph starts rendering the next frame, the prepareNode() function
         * is used to update the node with the new texture. Once it completes, it emits
         * textureInUse() which we connect to the FBO rendering thread's renderNext() to have
         * it start producing content into its current &quot;back buffer&quot;.
         *
         * This FBO rendering pipeline is throttled by vsync on the scene graph rendering thread.
         */</span>
        connect(m_renderThread<span class="operator">,</span> SIGNAL(textureReady(<span class="type">int</span><span class="operator">,</span><span class="type">QSize</span>))<span class="operator">,</span> node<span class="operator">,</span> SLOT(newTexture(<span class="type">int</span><span class="operator">,</span><span class="type">QSize</span>))<span class="operator">,</span> <span class="type">Qt</span><span class="operator">::</span>DirectConnection);
        connect(node<span class="operator">,</span> SIGNAL(pendingNewTexture())<span class="operator">,</span> window()<span class="operator">,</span> SLOT(update())<span class="operator">,</span> <span class="type">Qt</span><span class="operator">::</span>QueuedConnection);
        connect(window()<span class="operator">,</span> SIGNAL(beforeRendering())<span class="operator">,</span> node<span class="operator">,</span> SLOT(prepareNode())<span class="operator">,</span> <span class="type">Qt</span><span class="operator">::</span>DirectConnection);
        connect(node<span class="operator">,</span> SIGNAL(textureInUse())<span class="operator">,</span> m_renderThread<span class="operator">,</span> SLOT(renderNext())<span class="operator">,</span> <span class="type">Qt</span><span class="operator">::</span>QueuedConnection);

        <span class="comment">// Get the production of FBO textures started..</span>
        <span class="type">QMetaObject</span><span class="operator">::</span>invokeMethod(m_renderThread<span class="operator">,</span> <span class="string">&quot;renderNext&quot;</span><span class="operator">,</span> <span class="type">Qt</span><span class="operator">::</span>QueuedConnection);
    }

    node<span class="operator">-</span><span class="operator">&gt;</span>setRect(boundingRect());

    <span class="keyword">return</span> node;
}

<span class="preprocessor">#include &quot;threadrenderer.moc&quot;</span></pre>
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<!-- @@@scenegraph/textureinthread/threadrenderer.cpp -->
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