graphics-bug

[Shepard@MCKENZIE.S&C.Dialnet.Symbolics.COM (Tom Shepard)]

    Date: Fri, 30 Nov 90 15:26+0100
    From: gmdzi!nieters%sphinx@ai.sri.com (Hans Nieters)

    The call of draw-polygon does not produce visible output in case of thickness 1
	    for skew lines in genera-8

    (graphics::draw-polygon  '(100 100 100 200 300 200 200 100) :thickness 1 :filled nil)

    Since it works for genera 7, i am surprised. Can it be repaired?

    Hans Nieters  

See the section 1Scan Conversion0, p. 154, section 6.3.2.2 in Book 10,
"Programming the User Interface".  Also see
2graphics:with-coordinate-mode 0in the User Interface Dictionary.
Each of the following will do what you're expecting.

(graphics:with-coordinate-mode (*standard-output* :center)
  (graphics::draw-polygon '(100 100 100 200 300 200 200 100)
			  :thickness 1
			  :filled nil))

(graphics::draw-polygon '(100 100 100 200 300 200 200 100)
			:thickness 1
			:filled nil
			:scale-thickness NIL)

(graphics::draw-polygon '(100 100 100 200 300 200 200 100)
			:thickness 0
			:filled nil)


I would suggest the last example in most cases, especially if you
are scaling.