[jitter] Re: GL feedback: what is it

not trying to be an ass, but:
http://en.wikipedia.org/wiki/Feedback

basically, the some of the output is fed back into the input.

the preview recipe has nothing to do with feedback.  it uses texture readback, an entirely different concept. the scene is captured to a texture, and that texture is shared between two opengl contexts in order to have a gpu enabled preview screen (the texture is "readback" into the preview window context).