Re: Graphics clipping question

[kanderso%dino.bbn.com@RELAY.CS.NET]

  Date: Thu, 2 Mar 89 16:46 PST
  From: William M. York <York@Chuck-Jones.ILA-West.Dialnet.Symbolics.COM>
  Subject: Graphics clipping question
  To: kanderso@DINO.BBN.COM, slug@Warbucks.AI.SRI.COM
  In-Reply-To: The message of 2 Mar 89 11:24 PST from kanderso@DINO.BBN.COM
  Message-ID: <19890303004631.2.YORK@Chuck-Jones.ILA-West.Dialnet.Symbolics.COM>
  
      Date: Thu, 02 Mar 89 14:24:35 -0500
      From: kanderso@DINO.BBN.COM
  
      I am trying to convert some graph drawing software to use GRAPHICS:
      functions rather than window operations, and one thing i'm having
      trouble with is clipping.  I need to be able to clip drawing
      operations to the rectangular outline of the graph.  My old software
      modified the TV:CLIPPING-REGION instance variable of the stream being
      drawn on, and that worked fine.  This doesn't work with GRAPHICS:
      functions because the stream you think you are drawing on often has
      nothing to do with the steam you are actually drawing on because you
      are in a maze of twistly little continuations all alike.
  
  Try:
  
  (graphics:with-room-for-graphics ()
    (graphics:with-clipping-path (t #'(lambda (s)
  				      (graphics:draw-rectangle 100 100 200 200 :stream s :filled nil)))
      (graphics:draw-circle 100 100 50)))
  
  You can construct an arbitrary clipping region by drawing a path that
  surrounds it.

I tried this too, but it has the same problem.  It seems like i'll
have to do most of the clipping myself.

k