c++ - 2 QOpenGLWidget 共享上下文导致崩溃

Question

我想解决我仍在处理的问题..那就是在不同的顶级窗口中使用共享着色器程序等同时渲染 2 个 QOpenGLWidgets。

我的第一次尝试是使用一个上下文，但没有成功。

目前 QOpenGLWidget 甚至可能吗？或者我必须去旧的 QGLWidget？还是用别的东西？

Qt::AA_ShareOpenGLContexts 的 testAttribute 返回 true 所以共享没有问题甚至 QOpenGLContext::areSharing 也返回 true。所以有些东西我想念或者我不知道。不使用线程。

调试输出:

MapExplorer true true true QOpenGLShaderProgram::bind: program is notvalid in the current context. MapExlorer paintGL ends MapExplorer truetrue true QOpenGLShaderProgram::bind: program is not valid in thecurrent context. MapExlorer paintGL endsQOpenGLFramebufferObject::bind() called from incompatible contextQOpenGLShaderProgram::bind: program is not valid in the currentcontext. QOpenGLShaderProgram::bind: program is not valid in thecurrent context. QOpenGLShaderProgram::bind: program is not valid inthe current context. QOpenGLFramebufferObject::bind() called fromincompatible context QOpenGLFramebufferObject::bind() called fromincompatible context

map View 初始化GL:

void MapView::initializeGL()
{
    this->makeCurrent();

    initializeOpenGLFunctions();

    // Initialize World
    world->initialize(this->context(), size(), worldCoords);

    // Initialize camera shader
    camera->initialize();

    // Enable depth testing
    glEnable(GL_DEPTH_TEST);
    glEnable(GL_CULL_FACE);

    glDepthFunc(GL_LEQUAL); // just testing new depth func

    glClearColor(0.65f, 0.77f, 1.0f, 1.0f);
}

map View 绘制GL:

void MapView::paintGL()
{
    this->makeCurrent();

    glDrawBuffer(GL_FRONT);
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

    world->draw(...);
}

MapExplorer 初始化GL:

void MapExplorer::initializeGL()
{
    this->makeCurrent();

    QOpenGLContext* _context = _mapView->context();
    _context->setShareContext(this->context());
    _context->create();

    this->context()->create();
    this->makeCurrent();

    initializeOpenGLFunctions();

    // Enable depth testing
    glEnable(GL_DEPTH_TEST);
    glEnable(GL_CULL_FACE);

    glDepthFunc(GL_LEQUAL); // just testing new depth func

    glClearColor(0.65f, 0.77f, 1.0f, 1.0f);
}

MapExplorer paintGL:

void MapExplorer::paintGL()
{
    this->makeCurrent();

    qDebug() << "MapExplorer" << QOpenGLContext::areSharing(this->context(), _mapView->context()) << (QOpenGLContext::currentContext() == this->context());

    QOpenGLShaderProgram* shader = world->getTerrainShader();
    qDebug() << shader->create();
    shader->bind(); // debug error "QOpenGLShaderProgram::bind: program is not valid in the current context."

    // We need the viewport size to calculate tessellation levels and the geometry shader also needs the viewport matrix
    shader->setUniformValue("viewportSize",   viewportSize);
    shader->setUniformValue("viewportMatrix", viewportMatrix);

    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

    qDebug() << "MapExlorer paintGL ends";

    //world->drawExplorerView(...);
}

Answer 1

嗨，我已经破解了 2 天了，终于找到了可以工作的东西。

主要引用是qt's threadrenderer example .

基本上我有一个QOpenglWidget，它有自己的上下文，还有一个后台线程绘制到从QOpenglWidget 强>. QOpenglWidget可以直接使用后台线程绘制的帧缓冲区。

以下是使事情正常进行的步骤:

1. 我有QOpenglWidget RenderEngine和后台线程 RenderWorker

   // the worker is a thread
   class RenderWorker : public QThread, protected QOpenGLFunctions
   {
       // the background thread's context and surface
       QOffscreenSurface *surface = nullptr;
       QOpenGLContext *context = nullptr;
   
       RenderWorker::RenderWorker()
       {
           context = new QOpenGLContext();
           surface = new QOffscreenSurface();
       }
   
       ...
   }
   
   // the engine is a QOpenglWidget
   class RenderEngine : public QOpenGLWidget, protected QOpenGLFunctions
   {
   protected:
       // overwrite
       void initializeGL() override;
       void resizeGL(int w, int h) override;
       void paintGL() override;
   
   private:
       // the engine has a background worker
       RenderWorker *m_worker = nullptr;
   
       ...
   }
   

2. 在QOpenglWidget 的initializeGL() 中创建和设置后台线程

   void RenderEngine::initializeGL()
   {
       initializeOpenGLFunctions();
   
       // done with current (QOpenglWidget's) context
       QOpenGLContext *current = context();
       doneCurrent();
   
       // create the background thread
       m_worker = new RenderWorker();
   
       // the background thread's context is shared from current
       QOpenGLContext *shared = m_worker->context;
       shared->setFormat(current->format());
       shared->setShareContext(current);
       shared->create();
   
       // must move the shared context to the background thread
       shared->moveToThread(m_worker);
   
       // setup the background thread's surface
       // must be created here in the main thread
       QOffscreenSurface *surface = m_worker->surface;
       surface->setFormat(shared->format());
       surface->create();
   
       // worker signal
       connect(m_worker, SIGNAL(started()), m_worker, SLOT(initializeGL()));
   
       // must move the thread to itself
       m_worker->moveToThread(m_worker);
   
       // the worker can finally start
       m_worker->start();
   }
   

3. 后台线程必须在自己的线程中初始化共享上下文

   void RenderWorker::initializeGL()
   {
       context->makeCurrent(surface);
       initializeOpenGLFunctions();
   }
   

4. 现在后台线程中绘制的任何帧缓冲区都可以被QOpenglWidget直接使用(作为纹理等)，例如在paintGL()功能。

据我所知，opengl 上下文有点绑定(bind)到线程。 Shared context和相应的surface必须在主线程中创建和设置，移动到另一个线程并在其中初始化，然后才可以终于用上了。