From f987da4c43eb96431a7b8d61521bf826fb0c5df0 Mon Sep 17 00:00:00 2001
From: Zach Pomerantz <zach@highfidelity.io>
Date: Fri, 18 Mar 2016 18:10:45 -0700
Subject: [PATCH] Move qml rendering to defined thread

---
 libraries/gl/src/gl/OffscreenQmlSurface.cpp | 509 ++++++++++----------
 libraries/gl/src/gl/OffscreenQmlSurface.h   |   4 +-
 2 files changed, 260 insertions(+), 253 deletions(-)

diff --git a/libraries/gl/src/gl/OffscreenQmlSurface.cpp b/libraries/gl/src/gl/OffscreenQmlSurface.cpp
index 6a780d74e2..c1203ad776 100644
--- a/libraries/gl/src/gl/OffscreenQmlSurface.cpp
+++ b/libraries/gl/src/gl/OffscreenQmlSurface.cpp
@@ -47,11 +47,10 @@ protected:
 
 private:
     QWindow* _renderWindow{ nullptr };
-    friend class OffscreenQmlRenderer;
+    friend class OffscreenQmlRenderThread;
     friend class OffscreenQmlSurface;
 };
 
-
 Q_DECLARE_LOGGING_CATEGORY(offscreenFocus)
 Q_LOGGING_CATEGORY(offscreenFocus, "hifi.offscreen.focus")
 
@@ -60,264 +59,274 @@ 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);
 
-class OffscreenQmlRenderer : public OffscreenGLCanvas {
-    friend class OffscreenQmlSurface;
+class OffscreenQmlRenderThread : public QThread {
 public:
+    OffscreenQmlRenderThread(OffscreenQmlSurface* surface, QOpenGLContext* shareContext);
 
-    OffscreenQmlRenderer(OffscreenQmlSurface* surface, QOpenGLContext* shareContext) : _surface(surface) {
-        OffscreenGLCanvas::create(shareContext);
+    virtual void run() override;
+    virtual bool event(QEvent *e) override;
 
-        _renderControl = new QMyQuickRenderControl();
+protected:
+    class Queue : public QQueue<QEvent*> {
+    public:
+        void add(QEvent::Type type);
+        QEvent* take();
 
-        // 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.
-        QQuickWindow::setDefaultAlphaBuffer(true);
-        // Weirdness...  QQuickWindow NEEDS to be created on the rendering thread, or it will refuse to render
-        // because it retains an internal 'context' object that retains the thread it was created on, 
-        // regardless of whether you later move it to another thread.
-        _quickWindow = new QQuickWindow(_renderControl);
-        _quickWindow->setColor(QColor(255, 255, 255, 0));
-        _quickWindow->setFlags(_quickWindow->flags() | static_cast<Qt::WindowFlags>(Qt::WA_TranslucentBackground));
-
-        // Qt 5.5
-        _renderControl->prepareThread(&_thread);
-        getContextObject()->moveToThread(&_thread);
-        moveToThread(&_thread);
-        _thread.setObjectName("QML Thread");
-        _thread.start();
-        post(INIT);
-    }
-
-    bool event(QEvent *e) {
-        switch (int(e->type())) {
-        case INIT:
-            {
-                QMutexLocker lock(&_mutex);
-                init();
-            }
-            return true;
-        case RENDER:
-            {
-                QMutexLocker lock(&_mutex);
-                render(&lock);
-            }
-            return true;
-        case RESIZE:
-            {
-                QMutexLocker lock(&_mutex);
-                resize();
-            }
-            return true;
-        case STOP:
-            {
-                QMutexLocker lock(&_mutex);
-                cleanup();
-            }
-            return true;
-        default:
-            return QObject::event(e);
-        }
-    }
-
-    void post(const QEvent::Type& type) {
-        QCoreApplication::postEvent(this, new QEvent(type));
-    }
+    private:
+        QMutex _mutex;
+        QWaitCondition _waitCondition;
+        bool _isWaiting{ false };
+    };
 
+    friend class OffscreenQmlSurface;
+    Queue _queue;
+    QMutex _mutex;
+    QWaitCondition _waitCondition;
 
 private:
+    // Event-driven methods
+    void init();
+    void render();
+    void resize();
+    void cleanup();
 
-    void setupFbo() {
-        using namespace oglplus;
-        _textures.setSize(_size);
-        _depthStencil.reset(new Renderbuffer());
-        Context::Bound(Renderbuffer::Target::Renderbuffer, *_depthStencil)
-            .Storage(
-            PixelDataInternalFormat::DepthComponent,
-            _size.x, _size.y);
-
-        _fbo.reset(new Framebuffer());
-        _fbo->Bind(Framebuffer::Target::Draw);
-        _fbo->AttachRenderbuffer(Framebuffer::Target::Draw, 
-            FramebufferAttachment::Depth, *_depthStencil);
-        DefaultFramebuffer().Bind(Framebuffer::Target::Draw);
-    }
-
-
-
-    void init() {
-        connect(_renderControl, &QQuickRenderControl::renderRequested, _surface, &OffscreenQmlSurface::requestRender);
-        connect(_renderControl, &QQuickRenderControl::sceneChanged, _surface, &OffscreenQmlSurface::requestUpdate);
-
-        if (!makeCurrent()) {
-            qWarning("Failed to make context current on render thread");
-            return;
-        }
-        _renderControl->initialize(_context);
-        setupFbo();
-        _escrow.setRecycler([this](GLuint texture){
-            _textures.recycleTexture(texture);
-        });
-        doneCurrent();
-    }
-
-    void cleanup() {
-        if (!makeCurrent()) {
-            qFatal("Failed to make context current on render thread");
-            return;
-        }
-        _renderControl->invalidate();
-
-        _fbo.reset();
-        _depthStencil.reset();
-        _textures.clear();
-
-        doneCurrent();
-
-        getContextObject()->moveToThread(QCoreApplication::instance()->thread());
-        _thread.quit();
-        _cond.wakeOne();
-    }
-
-    void resize() {
-        // Update our members
-        if (_quickWindow) {
-            _quickWindow->setGeometry(QRect(QPoint(), _newSize));
-            _quickWindow->contentItem()->setSize(_newSize);
-        }
-
-        // Qt bug in 5.4 forces this check of pixel ratio,
-        // even though we're rendering offscreen.
-        qreal pixelRatio = 1.0;
-        if (_renderControl && _renderControl->_renderWindow) {
-            pixelRatio = _renderControl->_renderWindow->devicePixelRatio();
-        } 
-
-        uvec2 newOffscreenSize = toGlm(_newSize * pixelRatio);
-        _textures.setSize(newOffscreenSize);
-        if (newOffscreenSize == _size) {
-            return;
-        }
-        _size = newOffscreenSize;
-
-        // Clear out any fbos with the old size
-        if (!makeCurrent()) {
-            qWarning("Failed to make context current on render thread");
-            return;
-        }
-
-        qDebug() << "Offscreen UI resizing to " << _newSize.width() << "x" << _newSize.height() << " with pixel ratio " << pixelRatio;
-        setupFbo();
-        doneCurrent();
-    }
-
-    void render(QMutexLocker *lock) {
-        if (_surface->_paused) {
-            return;
-        }
-
-        if (!makeCurrent()) {
-            qWarning("Failed to make context current on render thread");
-            return;
-        }
-
-        _renderControl->sync();
-        _cond.wakeOne();
-        lock->unlock();
-
-        using namespace oglplus;
-
-        _quickWindow->setRenderTarget(GetName(*_fbo), QSize(_size.x, _size.y));
-
-        try {
-            PROFILE_RANGE("qml_render")
-            TexturePtr texture = _textures.getNextTexture();
-            _fbo->Bind(Framebuffer::Target::Draw);
-            _fbo->AttachTexture(Framebuffer::Target::Draw, FramebufferAttachment::Color, *texture, 0);
-            _fbo->Complete(Framebuffer::Target::Draw);
-            {
-                _renderControl->render();
-                // FIXME The web browsers seem to be leaving GL in an error state.
-                // Need a debug context with sync logging to figure out why.
-                // for now just clear the errors
-                glGetError();
-            }
-            // FIXME probably unecessary
-            DefaultFramebuffer().Bind(Framebuffer::Target::Draw);
-            _quickWindow->resetOpenGLState();
-            _escrow.submit(GetName(*texture));
-            _lastRenderTime = usecTimestampNow();
-        } catch (std::runtime_error& error) {
-            qWarning() << "Failed to render QML " << error.what();
-        }
-    }
-
-    void aboutToQuit() {
-        QMutexLocker lock(&_quitMutex);
-        _quit = true;
-    }
-
-    static const uint64_t MAX_SHUTDOWN_WAIT_SECS = 2;
-    void stop() {
-        if (_thread.isRunning()) {
-            qDebug() << "Stopping QML render thread " << _thread.currentThreadId();
-            {
-                QMutexLocker lock(&_mutex);
-                post(STOP);
-            }
-            auto start = usecTimestampNow();
-            auto now = usecTimestampNow();
-            bool shutdownClean = false;
-            while (now - start < (MAX_SHUTDOWN_WAIT_SECS * USECS_PER_SECOND)) {
-                QMutexLocker lock(&_mutex);
-                if (_cond.wait(&_mutex, MSECS_PER_SECOND)) {
-                    shutdownClean = true;
-                    break;
-                }
-                now = usecTimestampNow();
-            }
-
-            if (!shutdownClean) {
-                qWarning() << "Failed to shut down the QML render thread";
-            }
-
-        } else {
-            qDebug() << "QML render thread already completed";
-        }
-    }
-
-    bool allowNewFrame(uint8_t fps) {
-        auto minRenderInterval = USECS_PER_SECOND / fps;
-        auto lastInterval = usecTimestampNow() - _lastRenderTime;
-        return (lastInterval > minRenderInterval);
-    }
+    // Helper methods
+    void setupFbo();
+    bool allowNewFrame(uint8_t fps);
 
+    // Rendering members
+    OffscreenGLCanvas _canvas;
     OffscreenQmlSurface* _surface{ nullptr };
     QQuickWindow* _quickWindow{ nullptr };
     QMyQuickRenderControl* _renderControl{ nullptr };
-
-    QThread _thread;
-    QMutex _mutex;
-    QWaitCondition _cond;
-    QMutex _quitMutex;
-
-    QSize _newSize;
-    bool _quit;
     FramebufferPtr _fbo;
     RenderbufferPtr _depthStencil;
-    uvec2 _size{ 1920, 1080 };
-    uint64_t _lastRenderTime{ 0 };
     TextureRecycler _textures;
     GLTextureEscrow _escrow;
+
+    uint64_t _lastRenderTime{ 0 };
+    uvec2 _size{ 1920, 1080 };
+    QSize _newSize;
+    bool _quit{ false };
 };
 
+void OffscreenQmlRenderThread::Queue::add(QEvent::Type type) {
+    QMutexLocker locker(&_mutex);
+    enqueue(new QEvent(type));
+    if (_isWaiting) {
+        _waitCondition.wakeOne();
+    }
+}
+
+QEvent* OffscreenQmlRenderThread::Queue::take() {
+    QMutexLocker locker(&_mutex);
+    if (size() == 0) {
+        _isWaiting = true;
+        _waitCondition.wait(&_mutex);
+        _isWaiting = false;
+    }
+    QEvent* e = dequeue();
+    return e;
+}
+ 
+OffscreenQmlRenderThread::OffscreenQmlRenderThread(OffscreenQmlSurface* surface, QOpenGLContext* shareContext) : _surface(surface) {
+    _canvas.create(shareContext);
+    _renderControl = new QMyQuickRenderControl();
+    QQuickWindow::setDefaultAlphaBuffer(true);
+    // Create a QQuickWindow that is associated with our render control.
+    // This window never gets created or shown, meaning that it will never get an underlying native (platform) window.
+    // NOTE: Must be created on the main thread so that OffscreenQmlSurface can send it events
+    // NOTE: Must be created on the rendering thread or it will refuse to render,
+    //       so we wait until after its ctor to move object/context to this thread.
+    _quickWindow = new QQuickWindow(_renderControl);
+    _quickWindow->setColor(QColor(255, 255, 255, 0));
+    _quickWindow->setFlags(_quickWindow->flags() | static_cast<Qt::WindowFlags>(Qt::WA_TranslucentBackground));
+
+    // We can prepare, but we must wait to start() the thread until after the ctor
+    _renderControl->prepareThread(this);
+    _canvas.getContextObject()->moveToThread(this);
+    moveToThread(this);
+
+    _queue.add(INIT);
+}
+
+void OffscreenQmlRenderThread::run() {
+    while (!_quit) {
+        QEvent* e = _queue.take();
+        event(e);
+        delete e;
+    }
+}
+
+bool OffscreenQmlRenderThread::event(QEvent *e) {
+    switch (int(e->type())) {
+    case INIT:
+        init();
+        return true;
+    case RENDER:
+        render();
+        return true;
+    case RESIZE:
+        resize();
+        return true;
+    case STOP:
+        cleanup();
+        return true;
+    default:
+        return QObject::event(e);
+    }
+}
+
+void OffscreenQmlRenderThread::setupFbo() {
+    using namespace oglplus;
+    _textures.setSize(_size);
+    _depthStencil.reset(new Renderbuffer());
+    Context::Bound(Renderbuffer::Target::Renderbuffer, *_depthStencil)
+        .Storage(
+        PixelDataInternalFormat::DepthComponent,
+        _size.x, _size.y);
+
+    _fbo.reset(new Framebuffer());
+    _fbo->Bind(Framebuffer::Target::Draw);
+    _fbo->AttachRenderbuffer(Framebuffer::Target::Draw,
+        FramebufferAttachment::Depth, *_depthStencil);
+    DefaultFramebuffer().Bind(Framebuffer::Target::Draw);
+}
+
+void OffscreenQmlRenderThread::init() {
+    connect(_renderControl, &QQuickRenderControl::renderRequested, _surface, &OffscreenQmlSurface::requestRender);
+    connect(_renderControl, &QQuickRenderControl::sceneChanged, _surface, &OffscreenQmlSurface::requestUpdate);
+
+    if (!_canvas.makeCurrent()) {
+        qWarning("Failed to make context current on render thread");
+        return;
+    }
+    _renderControl->initialize(_canvas.getContext());
+    setupFbo();
+    _escrow.setRecycler([this](GLuint texture){
+        _textures.recycleTexture(texture);
+    });
+    _canvas.doneCurrent();
+}
+
+void OffscreenQmlRenderThread::cleanup() {
+    if (!_canvas.makeCurrent()) {
+        qFatal("Failed to make context current on render thread");
+        return;
+    }
+    _renderControl->invalidate();
+
+    _fbo.reset();
+    _depthStencil.reset();
+    _textures.clear();
+
+    _canvas.doneCurrent();
+
+    _canvas.getContextObject()->moveToThread(QCoreApplication::instance()->thread());
+
+    _quit = true;
+}
+
+void OffscreenQmlRenderThread::resize() {
+    // Lock _newSize changes
+    QMutexLocker locker(&_mutex);
+
+    // Update our members
+    if (_quickWindow) {
+        _quickWindow->setGeometry(QRect(QPoint(), _newSize));
+        _quickWindow->contentItem()->setSize(_newSize);
+    }
+
+    // Qt bug in 5.4 forces this check of pixel ratio,
+    // even though we're rendering offscreen.
+    qreal pixelRatio = 1.0;
+    if (_renderControl && _renderControl->_renderWindow) {
+        pixelRatio = _renderControl->_renderWindow->devicePixelRatio();
+    }
+
+    uvec2 newOffscreenSize = toGlm(_newSize * pixelRatio);
+    _textures.setSize(newOffscreenSize);
+    if (newOffscreenSize == _size) {
+        return;
+    }
+    _size = newOffscreenSize;
+
+    // Clear out any fbos with the old size
+    if (!_canvas.makeCurrent()) {
+        qWarning("Failed to make context current on render thread");
+        return;
+    }
+
+    qDebug() << "Offscreen UI resizing to " << _newSize.width() << "x" << _newSize.height() << " with pixel ratio " << pixelRatio;
+
+    locker.unlock();
+
+    setupFbo();
+    _canvas.doneCurrent();
+}
+
+void OffscreenQmlRenderThread::render() {
+    if (_surface->_paused) {
+        return;
+    }
+
+    if (!_canvas.makeCurrent()) {
+        qWarning("Failed to make context current on render thread");
+        return;
+    }
+
+    QMutexLocker locker(&_mutex);
+    _renderControl->sync();
+    _waitCondition.wakeOne();
+    locker.unlock();
+
+    using namespace oglplus;
+
+    _quickWindow->setRenderTarget(GetName(*_fbo), QSize(_size.x, _size.y));
+
+    try {
+        PROFILE_RANGE("qml_render")
+            TexturePtr texture = _textures.getNextTexture();
+        _fbo->Bind(Framebuffer::Target::Draw);
+        _fbo->AttachTexture(Framebuffer::Target::Draw, FramebufferAttachment::Color, *texture, 0);
+        _fbo->Complete(Framebuffer::Target::Draw);
+        {
+            _renderControl->render();
+            // FIXME The web browsers seem to be leaving GL in an error state.
+            // Need a debug context with sync logging to figure out why.
+            // for now just clear the errors
+            glGetError();
+        }
+        // FIXME probably unecessary
+        DefaultFramebuffer().Bind(Framebuffer::Target::Draw);
+        _quickWindow->resetOpenGLState();
+        _escrow.submit(GetName(*texture));
+        _lastRenderTime = usecTimestampNow();
+    } catch (std::runtime_error& error) {
+        qWarning() << "Failed to render QML " << error.what();
+    }
+}
+
+bool OffscreenQmlRenderThread::allowNewFrame(uint8_t fps) {
+    auto minRenderInterval = USECS_PER_SECOND / fps;
+    auto lastInterval = usecTimestampNow() - _lastRenderTime;
+    return (lastInterval > minRenderInterval);
+}
+
 OffscreenQmlSurface::OffscreenQmlSurface() {
 }
 
+static const uint64_t MAX_SHUTDOWN_WAIT_SECS = 2;
 OffscreenQmlSurface::~OffscreenQmlSurface() {
     QObject::disconnect(&_updateTimer);
     QObject::disconnect(qApp);
-    _renderer->stop();
+
+    qDebug() << "Stopping QML render thread " << _renderer->currentThreadId();
+    _renderer->_queue.add(STOP);
+    if (!_renderer->wait(MAX_SHUTDOWN_WAIT_SECS * USECS_PER_SECOND)) {
+        qWarning() << "Failed to shut down the QML render thread";
+    }
+
     delete _rootItem;
     delete _renderer;
     delete _qmlComponent;
@@ -326,15 +335,16 @@ OffscreenQmlSurface::~OffscreenQmlSurface() {
 
 void OffscreenQmlSurface::onAboutToQuit() {
     QObject::disconnect(&_updateTimer);
-    // Disconnecting the update timer is insufficient, since the renderer
-    // may attempting to render already, so we need to explicitly tell the renderer 
-    // to stop
-    _renderer->aboutToQuit(); 
 }
 
 void OffscreenQmlSurface::create(QOpenGLContext* shareContext) {
-    _renderer = new OffscreenQmlRenderer(this, shareContext);
+    _renderer = new OffscreenQmlRenderThread(this, shareContext);
+    _renderer->moveToThread(_renderer);
+    _renderer->setObjectName("QML Renderer Thread");
+    _renderer->start();
+
     _renderer->_renderControl->_renderWindow = _proxyWindow;
+
     // Create a QML engine.
     _qmlEngine = new QQmlEngine;
     if (!_qmlEngine->incubationController()) {
@@ -383,11 +393,11 @@ void OffscreenQmlSurface::resize(const QSize& newSize_) {
     }
 
     {
-        QMutexLocker _locker(&(_renderer->_mutex));
+        QMutexLocker locker(&(_renderer->_mutex));
         _renderer->_newSize = newSize;
     }
 
-    _renderer->post(RESIZE);
+    _renderer->_queue.add(RESIZE);
 }
 
 QQuickItem* OffscreenQmlSurface::getRootItem() {
@@ -487,14 +497,11 @@ void OffscreenQmlSurface::updateQuick() {
     }
 
     if (_render) {
-        QMutexLocker lock(&(_renderer->_mutex));
-        _renderer->post(RENDER);
-        while (!_renderer->_cond.wait(&(_renderer->_mutex), 100)) {
-            if (_renderer->_quit) {
-                return;
-            }
-            qApp->processEvents();
-        }
+        // Lock the GUI size while syncing
+        QMutexLocker locker(&(_renderer->_mutex));
+        _renderer->_queue.add(RENDER);
+        _renderer->_waitCondition.wait(&(_renderer->_mutex));
+
         _render = false;
     }
 
diff --git a/libraries/gl/src/gl/OffscreenQmlSurface.h b/libraries/gl/src/gl/OffscreenQmlSurface.h
index 9142e7f2ef..f30a9754ff 100644
--- a/libraries/gl/src/gl/OffscreenQmlSurface.h
+++ b/libraries/gl/src/gl/OffscreenQmlSurface.h
@@ -84,8 +84,8 @@ private slots:
     void updateQuick();
 
 private:
-    friend class OffscreenQmlRenderer;
-    OffscreenQmlRenderer* _renderer{ nullptr };
+    friend class OffscreenQmlRenderThread;
+    OffscreenQmlRenderThread* _renderer{ nullptr };
     QQmlEngine* _qmlEngine{ nullptr };
     QQmlComponent* _qmlComponent{ nullptr };
     QQuickItem* _rootItem{ nullptr };