title: How to use native OpenGL with Qt 5.4?
body: <p>I want to use Qt 5.4 to create a window and render with normal OpenGL functions some stuff in that window. In the last few days, I read a lot about the Qt classes and how to initialize OpenGL and so on. I think, the main classes I have to deal with are QOpenGLWindow or QOpenGLWidget, but there are the QSurface and some other classes too. Now I am very unsure about what doing next and which class I should use to use the plain OpenGL functions, later. Can someone explain more clearly to me what I have to do to set up a Qt GUI in which I can use plain OpenGL?</p>
  
  <p>Some other questions from me are:</p>
  
  <ul>
  <li>At which point does Qt create a plain OpenGL context? Do I have to use the QOpenGLContext?</li>
  <li>What is exactly the difference between a QSurface and a QOpenGLWindow? In the QOpenGLWindow example both classes are used.</li>
  <li>Is it possible to use glew besides this qt stuff? Here are some question on, which deal with setting up glew with qt, but I think that I did not get the real point of why glew is needed.</li>
  </ul>
  
  <p>Edit: I discussed this question with a colleague and our only conclusion was to use Offscreen-Rendering. Does anyone know another solution?</p>