I am currently using sgl to draw to a window, and using the screenshot progrm 
to convert tie picture to a .png file.
Unfortunately, this seems to linut the png to screen size, and I need more 
pixels thatn that for my application.

So my guess is that I need to create an sgl-compatible opengl environment that 
draws toa bitmap instead of a window, and then use the tools available to write 
that bitmap out as a .png file.

Trouble is, I don't know how to get a bitmap out of sgl.

Here's the function I use to vreate the window and call a function called 
drawer to draw into it.

(define (environ drawer)
  #;(printf "in environ\n")
  (define my-canvas%
    (class* canvas% ()
      (inherit with-gl-context swap-gl-buffers)
      (define/override (on-paint) ; When is on-paint caled?
        (printf "on-paint ~s~n" (count))
            (lambda ()
              #;(printf "call drawer~n")
              #;(printf "returned from drawer~n")

      (define/override (on-size width height) ; Is this what is called when 
resizing the window with a mouse?
            (lambda ()
              (resize width height)
      (super-instantiate () (style '(gl))) ; What is this?
  #;(printf "before win~n")
  (define win (new frame% (label "OpenGl Test")
                               (min-width 600)
                               (min-height 600)))
  #;(printf "before my-canvas~n")
  (define gl (new my-canvas% (parent win)))
  #;(printf "before show~n")
  (send win show #t)  ;  presumably this runs the on-paint method.
  ;     But why does it get called three times?
  #;(printf "out-environ~n")

-- hendrik

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