;;; Procedure:
;;;   new-no-failure
;;; Parameters:
;;;   side, an integer
;;;   color, an RGB list
;;; Purpose:
;;;   Creates a new image with the universal sign for "No Fs".
;;;   The image has width side and height side.
;;;   The F in the image has the specified color.
;;; Produces:
;;;   Nothing.  You call this only for the side effect of
;;;   drawing a new image.
;;; Preconditions:
;;;   Must be called from within Script-Fu.
;;; Postconditions:
;;;   A new image appears on the screen.
(define new-no-failure
  (lambda (side color)
    (let ((image (create-image side side))
          (unit (/ side 32)))
      ; Draw everything on white
      (set-bgcolor WHITE)
      ; Draw the silly letter F in the specified color
      (set-fgcolor color)
      (gimp-brushes-set-brush "Circle (11)")
      (line image (* unit 12) (* unit 5) 
                  (* unit 20) (* unit 5))
      (line image (* unit 12) (* unit 5)
                  (* unit 12) (* unit 27))
      (line image (* unit 12) (* unit 14)
                  (* unit 18) (* unit 14))
      ; Draw the nice red circle.
      (set-fgcolor RED)
      (set-brush "Circle (07)")
      (select-ellipse image REPLACE
                      unit unit 
                      (- side unit unit) (- side unit unit))
      (stroke image)
      (select-nothing image)
      ; Now we're ready to draw the slash.  Basic math tells us that
      ; the endpoints are offset by radius/(sqrt 2) from the center 
      ; of the circle.
      ; direction.
      (let* ((center (/ side 2))
             (radius (- center unit))
             (offset (/ radius (sqrt 2))))
        (line image
              (- center offset) (- center offset)
              (+ center offset) (+ center offset)))
      ; Display the image
      (show-image image)
      ; And return the image 
      image)))