The RectControl.Drawinto command comes with the caveat
This method does not work with HTMLViewer and OpenGLSurface.
Is this a permanent condition or will this be addressed in the near future so a screenshot can be taken of an opengl surface?
It will not ever work for HTMLViewer.
If your only concern is OpenGL, it can take screenshots itself: https://stackoverflow.com/questions/5844858/how-to-take-screenshot-in-opengl