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From: lily@mudos.ann-arbor.mi.us (Russ Woodroofe)
Newsgroups: comp.sys.apple2
Subject: Re: Assembler Line Drawing Code
Message-ID: <1991Dec01.234148.1845@mudos.ann-arbor.mi.us>
Date: 1 Dec 91 23:41:48 GMT
References: <1991Nov30.210632.8025@reed.edu>
Organization: The Programmer's Pit Stop, Ann Arbor MI
Lines: 29


        Look in the ROMs.  There are routines built in that will draw lines
yes, on page 1 OR 2.  (HLIN from BASIC).  Routines you will need:
(taken from Assembly language for the Applesoft Programmer)
HGR $F3E2     Set page one as current page, sets hgr mode on
              (HGR from Applesoft)
HGR2 $F3D8    Above, but for page 2, and full screen
(HGR2 from Applesoft)
SETHCOL $F6EC Put Applesoft color code (1-7) in the x reg and call
converts to a bit mask and stores in $E4 
              (HCOLOR= from Applesoft)
HPOSN $F411   Position hires cursor.  Y reg=High byte horizontal position
			X reg=Low byte horizontal position
			A reg=vertical postion
              This also copies the contents of $E4 to $1C
HPLOT $F457   Plot a point.  Registers as HPOSN.  Calls HPOSN to get point
(HPLOT from Applesoft)
HLIN $F53A    Draws a line from last point to specified point.
X reg=Horizontal High byte, YA reg=horizontal low byte
Y reg=vertical
(HLIN from Applesoft)
If you need to switch pages without calling HGR/HGR2, put the MSB of the
graphics page in $E6 (ie $20 for 1, $40 for 2)
      I've written some graphics stuff before, so I can be of SOME help
if you want to mail me... I never figured out the stuff about reading
the scan to avoid flicker though... oh well.
 
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