threadrenderer.cpp Example File

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#include "threadrenderer.h" #include "logorenderer.h" #include <QtCore/QMutex> #include <QtCore/QThread> #include <QtGui/QOpenGLContext> #include <QtGui/QOpenGLFramebufferObject> #include <QtGui/QGuiApplication> #include <QtGui/QOffscreenSurface> #include <QtQuick/QQuickWindow> #include <qsgsimpletexturenode.h> QList<QThread *> ThreadRenderer::threads; /* * 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 */ class RenderThread : public QThread { Q_OBJECT public: RenderThread(const QSize &size) : surface(0) , context(0) , m_renderFbo(0) , m_displayFbo(0) , m_logoRenderer(0) , m_size(size) { ThreadRenderer::threads << this; } QOffscreenSurface *surface; QOpenGLContext *context; public slots: void renderNext() { context->makeCurrent(surface); if (!m_renderFbo) { // Initialize the buffers and renderer QOpenGLFramebufferObjectFormat format; format.setAttachment(QOpenGLFramebufferObject::CombinedDepthStencil); m_renderFbo = new QOpenGLFramebufferObject(m_size, format); m_displayFbo = new QOpenGLFramebufferObject(m_size, format); m_logoRenderer = new LogoRenderer(); m_logoRenderer->initialize(); } m_renderFbo->bind(); context->functions()->glViewport(0, 0, m_size.width(), m_size.height()); m_logoRenderer->render(); // We need to flush the contents to the FBO before posting // the texture to the other thread, otherwise, we might // get unexpected results. context->functions()->glFlush(); m_renderFbo->bindDefault(); qSwap(m_renderFbo, m_displayFbo); emit textureReady(m_displayFbo->texture(), m_size); } void shutDown() { context->makeCurrent(surface); delete m_renderFbo; delete m_displayFbo; delete m_logoRenderer; context->doneCurrent(); delete context; // schedule this to be deleted only after we're done cleaning up surface->deleteLater(); // Stop event processing, move the thread to GUI and make sure it is deleted. exit(); moveToThread(QGuiApplication::instance()->thread()); } signals: void textureReady(int id, const QSize &size); private: QOpenGLFramebufferObject *m_renderFbo; QOpenGLFramebufferObject *m_displayFbo; LogoRenderer *m_logoRenderer; QSize m_size; }; class TextureNode : public QObject, public QSGSimpleTextureNode { Q_OBJECT public: TextureNode(QQuickWindow *window) : m_id(0) , m_size(0, 0) , m_texture(0) , m_window(window) { // Our texture node must have a texture, so use the default 0 texture. m_texture = m_window->createTextureFromId(0, QSize(1, 1)); setTexture(m_texture); setFiltering(QSGTexture::Linear); } ~TextureNode() { delete m_texture; } signals: void textureInUse(); void pendingNewTexture(); public slots: // This function gets called on the FBO rendering thread and will store the // texture id and size and schedule an update on the window. void newTexture(int id, const QSize &size) { m_mutex.lock(); m_id = id; m_size = size; m_mutex.unlock(); // We cannot call QQuickWindow::update directly here, as this is only allowed // from the rendering thread or GUI thread. emit pendingNewTexture(); } // Before the scene graph starts to render, we update to the pending texture void prepareNode() { m_mutex.lock(); int newId = m_id; QSize size = m_size; m_id = 0; m_mutex.unlock(); if (newId) { delete m_texture; // note: include QQuickWindow::TextureHasAlphaChannel if the rendered content // has alpha. m_texture = m_window->createTextureFromId(newId, size); setTexture(m_texture); markDirty(DirtyMaterial); // This will notify the rendering thread that the texture is now being rendered // and it can start rendering to the other one. emit textureInUse(); } } private: int m_id; QSize m_size; QMutex m_mutex; QSGTexture *m_texture; QQuickWindow *m_window; }; ThreadRenderer::ThreadRenderer() : m_renderThread(0) { setFlag(ItemHasContents, true); m_renderThread = new RenderThread(QSize(512, 512)); } void ThreadRenderer::ready() { m_renderThread->surface = new QOffscreenSurface(); m_renderThread->surface->setFormat(m_renderThread->context->format()); m_renderThread->surface->create(); m_renderThread->moveToThread(m_renderThread); connect(window(), &QQuickWindow::sceneGraphInvalidated, m_renderThread, &RenderThread::shutDown, Qt::QueuedConnection); m_renderThread->start(); update(); } QSGNode *ThreadRenderer::updatePaintNode(QSGNode *oldNode, UpdatePaintNodeData *) { TextureNode *node = static_cast<TextureNode *>(oldNode); if (!m_renderThread->context) { QOpenGLContext *current = window()->openglContext(); // Some GL implementations requres that the currently bound context is // made non-current before we set up sharing, so we doneCurrent here // and makeCurrent down below while setting up our own context. current->doneCurrent(); m_renderThread->context = new QOpenGLContext(); m_renderThread->context->setFormat(current->format()); m_renderThread->context->setShareContext(current); m_renderThread->context->create(); m_renderThread->context->moveToThread(m_renderThread); current->makeCurrent(window()); QMetaObject::invokeMethod(this, "ready"); return 0; } if (!node) { node = new TextureNode(window()); /* 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. */ connect(m_renderThread, &RenderThread::textureReady, node, &TextureNode::newTexture, Qt::DirectConnection); connect(node, &TextureNode::pendingNewTexture, window(), &QQuickWindow::update, Qt::QueuedConnection); connect(window(), &QQuickWindow::beforeRendering, node, &TextureNode::prepareNode, Qt::DirectConnection); connect(node, &TextureNode::textureInUse, m_renderThread, &RenderThread::renderNext, Qt::QueuedConnection); // Get the production of FBO textures started.. QMetaObject::invokeMethod(m_renderThread, "renderNext", Qt::QueuedConnection); } node->setRect(boundingRect()); return node; } #include "threadrenderer.moc"

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