dvga.pas

unit dvga;
{$G+}     { generate 286 instructions -- needed for shl 6/8 }

{ for rect, should I inline the hline routine,
  and convert the rest to asm? }

interface
const
   maxx=319;
   maxy=199;
   maxcolors=256;

procedure setmcga;
procedure settext;
procedure pset(x,y:word; col:byte);
function pget(x,y:word):byte;
function kbhit:boolean;
function getkey:char;
procedure waitretrace;
procedure hline(x,y,len:word; col:byte);
procedure vline(x,y,len:word; col:byte);
procedure rect(x1,y1,x2,y2:word; col:byte);


implementation

procedure setmcga; assembler;
asm
   mov ax, $0013
   int $10
end;

procedure settext; assembler;
asm
   mov ax, $0003
   int $10
end;

procedure pset(x,y:word;col:byte); assembler;
asm
   push es
   mov ax, $a000
   mov es, ax
   mov bx, y
   mov ax, bx
   shl ax, 6
   shl bx, 8
   add ax, bx
   add ax, x
   mov di, ax
   mov al, col
   stosb
   pop es
end;

function pget(x,y:word):byte; assembler;
asm
   push es
   mov ax, $a000
   mov es, ax
   mov bx, y
   mov ax, bx
   shl ax, 6
   shl bx, 8
   add ax, bx
   add ax, x
   mov di, ax
   lodsb
   pop es
end;

function kbhit:boolean; assembler;
asm
   mov ax, $0100
   int $16
   mov al, 00
   jz @done
   mov ax, 1
@done:
end;

function getkey:char; assembler;
asm
   xor ax, ax
   int $16
   xor ah, ah
end;

procedure waitretrace; assembler;
asm
   mov dx,3dah
@l1:
   in al,dx
   and al,08h
   jnz @l1
@l2:
   in al,dx
   and al,08h
   jz @l2
   ret
end;

procedure hline(x,y,len:word;col:byte); assembler;
asm
   push es
   mov ax, $a000
   mov es, ax
   mov bx, y
   mov ax, bx
   shl ax, 6
   shl bx, 8
   add ax, bx
   add ax, x
   mov cx, len
   mov di, ax
   mov al, col
   rep stosb
   pop es
end;

procedure vline(x,y,len:word; col:byte); assembler;
asm
   push es
   mov ax, $a000
   mov es, ax
   mov bx, y
   mov ax, bx
   shl ax, 6
   shl bx, 8
   add ax, bx
   add ax, x
   mov cx, len
   mov di, ax
   mov al, col
@l:
   stosb
   add di, 319
   loop @l
   pop es
end;

procedure rect(x1,y1,x2,y2:word; col:byte);
var i,len:word;
begin
   len:=x2-x1;
   for i:=y1 to y2 do
      hline(x1, i, len, col);
end;

end.