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From: ForthNet@willett.UUCP (ForthNet articles from GEnie)
Newsgroups: comp.lang.forth
Subject: GRAPHICS BUGS
Message-ID: <199.UUL1.3#5129@willett.UUCP>
Date: 5 Jan 90 20:43:57 GMT
Organization: Latest Link in ForthNet Chain
Lines: 61


 Date: 01-02-90 (05:48)              Number: 1696
   To: MIKE SPERL                    Refer#: NONE
 From: MARK SMILEY                     Read: NO
 Subj: GRAPHICS BUGS                 Status: PUBLIC MESSAGE

 Mike,
    Alas, FILL-ELLIPSE  (renamed to FILL_ELLIPSE) didn't work
 for me.  In EGA or VGA640 mode, try:
    : FF  ( -- )     \ draws a centered filled ellipse
         hres @ 2/  vres @ 2/  2DUP  SWAP 2/  SWAP 2/  ;
         FILL_ELLIPSE  ;   FF
    It only filled the horizontal line one away from the bottom
 line of the ellipse.
    On the other hand, EGA 300 200 20 30 FILL_ELLIPSE
 filled only a thin vertical line to the left of center.
 .
    In checking out FILL_ELLIPSE, I discovered another bug in
 GRAFKRNL.SEQ.
 .
 DOT ( x y color -- ) and CDOT didn't work properly, due to the
 value of COLOR being used in  set.res2.  The change I made is
 simple, though you may know a better way:
 .
 \ write mode 2 (assumes di=color)
 label set.res2di    \ load set/reset reg. w/ color
     mov dx, # $3ce  \ address graphics contrl. regs.
     mov ax, # $0f01 \ al = enable set/res. reg. index = 1
     out dx, ax      \ ah = all 8 bits on, written to $3cf
     xor ax, ax      \ al = set/reset reg. index = 0
     XCHG BX, DI     \ save BX
     MOV AH, BL      \ send color (host data to vga)
                     \ Can't MOV AH, DI
     out dx, ax
     XCHG BX, DI     \ restore BX (necessary for routines that
                     \ compute the pixel address before calling
                     \ this routine.).  Restores DI just in case
                     \ it's needed by the calling routine.
     ret  c;
 .
 code ega.dot ( x y color -- )
     POP DI                       \ color in di
     pop cx  pop dx       \ dx = col, cx = row (dx=x, cx=y)
 +code ega.d
     push es                      \ save forth; color in di
     call ega.pel.addr
     call set.res2DI    \ does: mov dx, # $3ce  \THE ONLY CHANGE
     not cl                       \ = 255 - cl 
     and cl, # 7                  \ = 0 to 7
     mov ax, # $108
     rol ah, cl                   \ position our bit
     out dx, ax                   \ mask to data reg
     mov ax, di                   \ color in ega = 0..15
     or es: 0 [bx], al            \ write pixel
     call restr.state
     pop es
     next  c;

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