8 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 viewports for different windows
       [w1  (open-viewport "viewport 1" 300 300)]
       [w2  (open-viewport "viewport 2" 200 500)]
       ; d1 and d2 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

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1	Basic Commands
2	Position Operations
3	Color Operations
4	Draw, Clear, and Flip Operations
5	World Operations
6	Miscellaneous Operations
7	An Example
8	A More Complicated Example
9	Protecting Graphics Operations
10	Mouse Operations
11	Keyboard Operations
12	Flushing
13	Graphics Library as a Unit