A More Complicated Example

The use of multiple viewports, viewport descriptors, drawing operations for multiple viewports is as easy as the use of a single viewport:

  > (open-graphics)
  > (let* ( ; w1 and w2 are viewport descriptors for different windows
           [w1  (open-viewport "viewport 1" 300 300)]
           [w2  (open-viewport "viewport 2" 200 500)]

          ; d1 and d2 are functions that draw lines in different viewports
           [d1  (draw-line w1)]
           [d2  (draw-line w2)])

      ; draws a line in viewport labeled "viewport 1"
      (d1 (make-posn 100 5) (make-posn 5 100))

      ; draws a line in viewport labeled "viewport 2"
      (d2 (make-posn 100 100) (make-posn 101 400)))

  ; we no longer have access to viewports 1 and 2, 
  ; since their descriptors did not escape the let.

  > (close-graphics)           ; removes the viewports