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From: hahnt@kiss.informatik.tu-muenchen.de.informatik.tu-muenchen.dbp.de
Newsgroups: comp.lang.scheme
Subject: PC Scheme 3.03, %GRAPHICS-primitive no. 4
Message-ID: <3337@tuminfo1.lan.informatik.tu-muenchen.dbp.de>
Date: 10 Jul 90 19:36:19 GMT
Sender: news@lan.informatik.tu-muenchen.dbp.de
Reply-To: hahnt@kiss.informatik.tu-muenchen.de.informatik.tu-muenchen.dbp.de ()
Organization: Inst. fuer Informatik, TU Muenchen, W. Germany
Lines: 12

The following procedure shows that pixelvalues with a vertical position
greater than 255 are not gettable, although they are settable in video-modes
15, 16 and 18. 

(define *vm* 18) ;16 15

(define (test)
  (set-video-mode! *vm*)
  (do ((i 0 (1+ i)))
      ((begin (%graphics 1 0 i 15 0 0 0) 
              (<> 15 (%graphics 4 0 i 0 0 0 0)))
       (set-video-mode! 3) i)))