Now we render the background of the scene with our own OpenGL calls..

Qt Code: 
  1. #ifndef MAIN_H
  2. #define MAIN_H
  3.  
  4. #include <QtCore>
  5. #include <QtGui>
  6. #include <QtOpenGL>
  7.  
  8. using namespace std;
  9.  
  10. class OpenGLScene : public QGraphicsScene
  11. {
  12. public:
  13.     OpenGLScene() {
  14.  
  15.     }
  16. protected:
  17.     void drawBackground(QPainter *painter, const QRectF &);
  18. };
  19.  
  20. void OpenGLScene::drawBackground(QPainter *painter, const QRectF &)
  21. {
  22.     /*if (painter->paintEngine()->type() != QPaintEngine::OpenGL) {
  23.         qWarning("OpenGLScene: drawBackground needs a "
  24.                  "QGLWidget to be set as viewport on the "
  25.                  "graphics view");
  26.         return;
  27.     }*/
  28.     //
  29.     QColor m_backgroundColor = QColor("yellow");
  30.     glClearColor(m_backgroundColor.redF(),
  31.                  m_backgroundColor.greenF(),
  32.                  m_backgroundColor.blueF(), 1.0f);
  33.     glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
  34. }
  35.  
  36.  
  37. class MainWindow : public QMainWindow
  38. {
  39. public:
  40.     MainWindow(QWidget *parent = 0);
  41. private:
  42.     OpenGLScene *scene;
  43.     QGraphicsView *graphicsView;
  44. };
  45.  
  46.  
  47.  
  48. MainWindow::MainWindow(QWidget *parent) :
  49.     QMainWindow(parent)
  50. {
  51.     scene = new OpenGLScene();
  52.  
  53.     QPushButton* btn = new QPushButton("Test");
  54.     scene->addWidget(btn);
  55.  
  56.     graphicsView = new QGraphicsView(this);
  57.     graphicsView->setViewport(new QGLWidget(QGLFormat(QGL::SampleBuffers)));
  58.     graphicsView->setScene(scene);
  59.     graphicsView->setGeometry(QRect(50, 50, 500, 300));
  60.     graphicsView->show();
  61.  
  62.     this->setCentralWidget(graphicsView);
  63.  
  64. }
  65.  
  66. #endif // MAIN_H
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Aah! Something is wrong with this check! Did produce the same warning here. But the OpenGL stuff obviously works!

Joh