title: QGLWidget - faster grabFrameBuffer
body: <p>I have a kind of streaming application, which should capture the content of a window. In the window a QGLWidget draws the stuff. At the moment I am using <code>widget.grabFrameBuffer</code> in every draw cycle (has to be real time). The app uses 100% CPU and without the <code>widget.grabFrameBuffer</code> it drops to 10-20%. I figured out, that the call <code>image.bits()</code> (what I need, for sending the QImage data) creates a copy (not really good way of solving problem). Has somebody an idea how I could get the pointer to the frame buffer or image data, or do I have to use opengl commands?</p>