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50
51#include "threadrenderer.h"
52#include "logorenderer.h"
53
54#include <QtCore/QMutex>
55#include <QtCore/QThread>
56
57#include <QtGui/QOpenGLContext>
58#include <QtGui/QOpenGLFramebufferObject>
59#include <QtGui/QGuiApplication>
60#include <QtGui/QOffscreenSurface>
61
62#include <QtQuick/QQuickWindow>
63#include <qsgsimpletexturenode.h>
64
65QList<QThread *> ThreadRenderer::threads;
66
67/*
68 * The render thread shares a context with the scene graph and will
69 * render into two separate FBOs, one to use for display and one
70 * to use for rendering
71 */
72class RenderThread : public QThread
73{
74 Q_OBJECT
75public:
76 RenderThread(const QSize &size)
77 : surface(nullptr)
78 , context(nullptr)
79 , m_renderFbo(nullptr)
80 , m_displayFbo(nullptr)
81 , m_logoRenderer(nullptr)
82 , m_size(size)
83 {
84 ThreadRenderer::threads << this;
85 }
86
87 QOffscreenSurface *surface;
88 QOpenGLContext *context;
89
90public slots:
91 void renderNext()
92 {
93 context->makeCurrent(surface);
94
95 if (!m_renderFbo) {
96 // Initialize the buffers and renderer
97 QOpenGLFramebufferObjectFormat format;
98 format.setAttachment(QOpenGLFramebufferObject::CombinedDepthStencil);
99 m_renderFbo = new QOpenGLFramebufferObject(m_size, format);
100 m_displayFbo = new QOpenGLFramebufferObject(m_size, format);
101 m_logoRenderer = new LogoRenderer();
102 m_logoRenderer->initialize();
103 }
104
105 m_renderFbo->bind();
106 context->functions()->glViewport(x: 0, y: 0, width: m_size.width(), height: m_size.height());
107
108 m_logoRenderer->render();
109
110 // We need to flush the contents to the FBO before posting
111 // the texture to the other thread, otherwise, we might
112 // get unexpected results.
113 context->functions()->glFlush();
114
115 m_renderFbo->bindDefault();
116 qSwap(value1&: m_renderFbo, value2&: m_displayFbo);
117
118 emit textureReady(id: m_displayFbo->texture(), size: m_size);
119 }
120
121 void shutDown()
122 {
123 context->makeCurrent(surface);
124 delete m_renderFbo;
125 delete m_displayFbo;
126 delete m_logoRenderer;
127 context->doneCurrent();
128 delete context;
129
130 // schedule this to be deleted only after we're done cleaning up
131 surface->deleteLater();
132
133 // Stop event processing, move the thread to GUI and make sure it is deleted.
134 exit();
135 moveToThread(thread: QGuiApplication::instance()->thread());
136 }
137
138signals:
139 void textureReady(int id, const QSize &size);
140
141private:
142 QOpenGLFramebufferObject *m_renderFbo;
143 QOpenGLFramebufferObject *m_displayFbo;
144
145 LogoRenderer *m_logoRenderer;
146 QSize m_size;
147};
148
149
150
151class TextureNode : public QObject, public QSGSimpleTextureNode
152{
153 Q_OBJECT
154
155public:
156 TextureNode(QQuickWindow *window)
157 : m_id(0)
158 , m_size(0, 0)
159 , m_texture(nullptr)
160 , m_window(window)
161 {
162 // Our texture node must have a texture, so use the default 0 texture.
163 m_texture = m_window->createTextureFromId(id: 0, size: QSize(1, 1));
164 setTexture(m_texture);
165 setFiltering(QSGTexture::Linear);
166 }
167
168 ~TextureNode() override
169 {
170 delete m_texture;
171 }
172
173signals:
174 void textureInUse();
175 void pendingNewTexture();
176
177public slots:
178
179 // This function gets called on the FBO rendering thread and will store the
180 // texture id and size and schedule an update on the window.
181 void newTexture(int id, const QSize &size) {
182 m_mutex.lock();
183 m_id = id;
184 m_size = size;
185 m_mutex.unlock();
186
187 // We cannot call QQuickWindow::update directly here, as this is only allowed
188 // from the rendering thread or GUI thread.
189 emit pendingNewTexture();
190 }
191
192
193 // Before the scene graph starts to render, we update to the pending texture
194 void prepareNode() {
195 m_mutex.lock();
196 int newId = m_id;
197 QSize size = m_size;
198 m_id = 0;
199 m_mutex.unlock();
200 if (newId) {
201 delete m_texture;
202 // note: include QQuickWindow::TextureHasAlphaChannel if the rendered content
203 // has alpha.
204 m_texture = m_window->createTextureFromId(id: newId, size);
205 setTexture(m_texture);
206
207 markDirty(bits: DirtyMaterial);
208
209 // This will notify the rendering thread that the texture is now being rendered
210 // and it can start rendering to the other one.
211 emit textureInUse();
212 }
213 }
214
215private:
216
217 int m_id;
218 QSize m_size;
219
220 QMutex m_mutex;
221
222 QSGTexture *m_texture;
223 QQuickWindow *m_window;
224};
225
226ThreadRenderer::ThreadRenderer()
227 : m_renderThread(nullptr)
228{
229 setFlag(flag: ItemHasContents, enabled: true);
230 m_renderThread = new RenderThread(QSize(512, 512));
231}
232
233void ThreadRenderer::ready()
234{
235 m_renderThread->surface = new QOffscreenSurface();
236 m_renderThread->surface->setFormat(m_renderThread->context->format());
237 m_renderThread->surface->create();
238
239 m_renderThread->moveToThread(thread: m_renderThread);
240
241 connect(sender: window(), signal: &QQuickWindow::sceneGraphInvalidated, receiver: m_renderThread, slot: &RenderThread::shutDown, type: Qt::QueuedConnection);
242
243 m_renderThread->start();
244 update();
245}
246
247QSGNode *ThreadRenderer::updatePaintNode(QSGNode *oldNode, UpdatePaintNodeData *)
248{
249 TextureNode *node = static_cast<TextureNode *>(oldNode);
250
251 if (!m_renderThread->context) {
252 QOpenGLContext *current = window()->openglContext();
253 // Some GL implementations requres that the currently bound context is
254 // made non-current before we set up sharing, so we doneCurrent here
255 // and makeCurrent down below while setting up our own context.
256 current->doneCurrent();
257
258 m_renderThread->context = new QOpenGLContext();
259 m_renderThread->context->setFormat(current->format());
260 m_renderThread->context->setShareContext(current);
261 m_renderThread->context->create();
262 m_renderThread->context->moveToThread(thread: m_renderThread);
263
264 current->makeCurrent(surface: window());
265
266 QMetaObject::invokeMethod(obj: this, member: "ready");
267 return nullptr;
268 }
269
270 if (!node) {
271 node = new TextureNode(window());
272
273 /* Set up connections to get the production of FBO textures in sync with vsync on the
274 * rendering thread.
275 *
276 * When a new texture is ready on the rendering thread, we use a direct connection to
277 * the texture node to let it know a new texture can be used. The node will then
278 * emit pendingNewTexture which we bind to QQuickWindow::update to schedule a redraw.
279 *
280 * When the scene graph starts rendering the next frame, the prepareNode() function
281 * is used to update the node with the new texture. Once it completes, it emits
282 * textureInUse() which we connect to the FBO rendering thread's renderNext() to have
283 * it start producing content into its current "back buffer".
284 *
285 * This FBO rendering pipeline is throttled by vsync on the scene graph rendering thread.
286 */
287 connect(sender: m_renderThread, signal: &RenderThread::textureReady, receiver: node, slot: &TextureNode::newTexture, type: Qt::DirectConnection);
288 connect(sender: node, signal: &TextureNode::pendingNewTexture, receiver: window(), slot: &QQuickWindow::update, type: Qt::QueuedConnection);
289 connect(sender: window(), signal: &QQuickWindow::beforeRendering, receiver: node, slot: &TextureNode::prepareNode, type: Qt::DirectConnection);
290 connect(sender: node, signal: &TextureNode::textureInUse, receiver: m_renderThread, slot: &RenderThread::renderNext, type: Qt::QueuedConnection);
291
292 // Get the production of FBO textures started..
293 QMetaObject::invokeMethod(obj: m_renderThread, member: "renderNext", type: Qt::QueuedConnection);
294 }
295
296 node->setRect(boundingRect());
297
298 return node;
299}
300
301#include "threadrenderer.moc"
302

source code of qtdeclarative/examples/quick/scenegraph/textureinthread/threadrenderer.cpp