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 (open-viewport "viewport 1" 300 300)]
[w2 (open-viewport "viewport 2" 200 500)]
; \var{w1} and \var{w2} are viewport descriptors for different windows
[d1 (draw-line w1)]
[d2 (draw-line w2)])
; \var{d1} and \var{d2} are functions that draw lines in different viewports
(d1 (make-posn 100 5) (make-posn 5 100))
; draws a line in viewport labeled ``viewport 1''
(d2 (make-posn 100 100) (make-posn 101 400)))
; draws a line in viewport labeled ``viewport 2''
; we no longer have access to viewports 1 and 2,
; since their descriptors were local variables.
> (close-graphics) ; removes the viewports