title: Qt QOpenGLWidget wheelEvent strange behaviour
body: <p>I have the following class :</p>
  
  <pre><code>class Curve2DOpenGLWidget : public QOpenGLWidget, protected QOpenGLFunctions_3_3_Core {
  Q_OBJECT   
  public:
  
      Curve2DOpenGLWidget( QWidget* parent = nullptr );
      ~Curve2DOpenGLWidget();  
  
      void initializeGL() override;
      void resizeGL(int width, int height) override;
      void paintGL() override;
      void NativePaintGL();
  
  protected:
      void mousePressEvent(QMouseEvent *event) override;
      void mouseReleaseEvent(QMouseEvent *event) override;
      void mouseMoveEvent(QMouseEvent *event) override;
      void wheelEvent(QWheelEvent *event) override;
  
  };
  </code></pre>
  
  <p>I want to use wheelEvent to zoom in / zoom out in my scene.</p>
  
  <p>Here is the code :</p>
  
  <pre><code>void Curve2DOpenGLWidget::wheelEvent( QWheelEvent* event ) {
      QOpenGLWidget::wheelEvent(event);
      float numStep = (event-&gt;angleDelta().y() / 8) / 15;
      m_camera.MoveFront(numStep * 0.1f);
  }
  </code></pre>
  
  <p>It does what I want, but this event is not called when <strong>I move the mouse and use mouse wheel at the same time</strong>.</p>
  
  <p>This code works on all the other widgets I've implemented (QGraphicsView, etc.). I'm wondering if there is anything special to do on QOpenGLWidget ?</p>
  
  <p>I can't explain this behaviour... If it can help, I'm working on Ubuntu 14.04 LTS</p>