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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 -->
<div class="descr"> <a name="details"></a>
<pre class="cpp">
<span class="comment">/****************************************************************************
**
** 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."
**
** $QT_END_LICENSE$
**
****************************************************************************/</span>
<span class="preprocessor">#include "threadrenderer.h"</span>
<span class="preprocessor">#include "logorenderer.h"</span>
<span class="preprocessor">#include <QtCore/QMutex></span>
<span class="preprocessor">#include <QtCore/QThread></span>
<span class="preprocessor">#include <QtGui/QOpenGLContext></span>
<span class="preprocessor">#include <QtGui/QOpenGLFramebufferObject></span>
<span class="preprocessor">#include <QtGui/QGuiApplication></span>
<span class="preprocessor">#include <QtGui/QOffscreenSurface></span>
<span class="preprocessor">#include <QtQuick/QQuickWindow></span>
<span class="preprocessor">#include <qsgsimpletexturenode.h></span>
<span class="type">QList</span><span class="operator"><</span><span class="type">QThread</span> <span class="operator">*</span><span class="operator">></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">&</span>size)
: surface(nullptr)
<span class="operator">,</span> context(nullptr)
<span class="operator">,</span> m_renderFbo(nullptr)
<span class="operator">,</span> m_displayFbo(nullptr)
<span class="operator">,</span> m_logoRenderer(nullptr)
<span class="operator">,</span> m_size(size)
{
ThreadRenderer<span class="operator">::</span>threads <span class="operator"><</span><span class="operator"><</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">></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">></span>initialize();
}
m_renderFbo<span class="operator">-</span><span class="operator">></span>bind();
context<span class="operator">-</span><span class="operator">></span>functions()<span class="operator">-</span><span class="operator">></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">></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">></span>functions()<span class="operator">-</span><span class="operator">></span>glFlush();
m_renderFbo<span class="operator">-</span><span class="operator">></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">></span>texture()<span class="operator">,</span> m_size);
}
<span class="type">void</span> shutDown()
{
context<span class="operator">-</span><span class="operator">></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">></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">></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">></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">&</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(nullptr)
<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">></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() override
{
<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">&</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">></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(nullptr)
{
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">></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">></span>surface<span class="operator">-</span><span class="operator">></span>setFormat(m_renderThread<span class="operator">-</span><span class="operator">></span>context<span class="operator">-</span><span class="operator">></span>format());
m_renderThread<span class="operator">-</span><span class="operator">></span>surface<span class="operator">-</span><span class="operator">></span>create();
m_renderThread<span class="operator">-</span><span class="operator">></span>moveToThread(m_renderThread);
connect(window()<span class="operator">,</span> <span class="operator">&</span><span class="type"><a href="qquickwindow.html">QQuickWindow</a></span><span class="operator">::</span>sceneGraphInvalidated<span class="operator">,</span> m_renderThread<span class="operator">,</span> <span class="operator">&</span>RenderThread<span class="operator">::</span>shutDown<span class="operator">,</span> <span class="type">Qt</span><span class="operator">::</span>QueuedConnection);
m_renderThread<span class="operator">-</span><span class="operator">></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"><</span>TextureNode <span class="operator">*</span><span class="operator">></span>(oldNode);
<span class="keyword">if</span> (<span class="operator">!</span>m_renderThread<span class="operator">-</span><span class="operator">></span>context) {
<span class="type">QOpenGLContext</span> <span class="operator">*</span>current <span class="operator">=</span> window()<span class="operator">-</span><span class="operator">></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">></span>doneCurrent();
m_renderThread<span class="operator">-</span><span class="operator">></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">></span>context<span class="operator">-</span><span class="operator">></span>setFormat(current<span class="operator">-</span><span class="operator">></span>format());
m_renderThread<span class="operator">-</span><span class="operator">></span>context<span class="operator">-</span><span class="operator">></span>setShareContext(current);
m_renderThread<span class="operator">-</span><span class="operator">></span>context<span class="operator">-</span><span class="operator">></span>create();
m_renderThread<span class="operator">-</span><span class="operator">></span>context<span class="operator">-</span><span class="operator">></span>moveToThread(m_renderThread);
current<span class="operator">-</span><span class="operator">></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">"ready"</span>);
<span class="keyword">return</span> nullptr;
}
<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 "back buffer".
*
* This FBO rendering pipeline is throttled by vsync on the scene graph rendering thread.
*/</span>
connect(m_renderThread<span class="operator">,</span> <span class="operator">&</span>RenderThread<span class="operator">::</span>textureReady<span class="operator">,</span> node<span class="operator">,</span> <span class="operator">&</span>TextureNode<span class="operator">::</span>newTexture<span class="operator">,</span> <span class="type">Qt</span><span class="operator">::</span>DirectConnection);
connect(node<span class="operator">,</span> <span class="operator">&</span>TextureNode<span class="operator">::</span>pendingNewTexture<span class="operator">,</span> window()<span class="operator">,</span> <span class="operator">&</span><span class="type"><a href="qquickwindow.html">QQuickWindow</a></span><span class="operator">::</span>update<span class="operator">,</span> <span class="type">Qt</span><span class="operator">::</span>QueuedConnection);
connect(window()<span class="operator">,</span> <span class="operator">&</span><span class="type"><a href="qquickwindow.html">QQuickWindow</a></span><span class="operator">::</span>beforeRendering<span class="operator">,</span> node<span class="operator">,</span> <span class="operator">&</span>TextureNode<span class="operator">::</span>prepareNode<span class="operator">,</span> <span class="type">Qt</span><span class="operator">::</span>DirectConnection);
connect(node<span class="operator">,</span> <span class="operator">&</span>TextureNode<span class="operator">::</span>textureInUse<span class="operator">,</span> m_renderThread<span class="operator">,</span> <span class="operator">&</span>RenderThread<span class="operator">::</span>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">"renderNext"</span><span class="operator">,</span> <span class="type">Qt</span><span class="operator">::</span>QueuedConnection);
}
node<span class="operator">-</span><span class="operator">></span>setRect(boundingRect());
<span class="keyword">return</span> node;
}
<span class="preprocessor">#include "threadrenderer.moc"</span>
</pre>
</div>
<!-- @@@scenegraph/textureinthread/threadrenderer.cpp -->
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