Category : Assembly Language Source Code
Archive   : VGAKIT60.ZIP
Filename : LINE.ASM

include model.inc

;
; VGAKIT Version 6.0
;
; Copyright 1988,89,90,91,92,93,94 John Bridges
; Free for use in commercial, shareware or freeware applications
;
; LINE.ASM
;
;
.code
public bline

callpt macro ;C order of parameter passing
push [color]
push di
push si
call [func]
add sp,6
endm

;bline(x,y,x2,y2,func())
;
;input : endpoints of line and function to use as point
;output : nothing
;utility : draw line between endpoints using function
; converted c routine
;
bline proc uses si di, x1:word,y1:word,x2:word,y2:word,color:word,func:ptr proc
local cnt:word,acc:word
local deltax:word,deltay:word,dirx:word,diry:word

mov si,[x1]
mov di,[y1]
xor ax,ax
mov [acc],ax
mov ax,[x2]
sub ax,si
mov dx,1
jns nosx
neg ax
mov dx,-1
nosx: mov [dirx],dx
mov [deltax],ax
mov ax,[y2]
sub ax,di
mov dx,1
jns nosy
neg ax
mov dx,-1
nosy: mov [diry],dx
mov [deltay],ax
cmp ax,[deltax]
jge ylp
callpt
mov ax,[deltax]
mov [cnt],ax
lp1:
dec [cnt]
js done
add si,[dirx]
mov ax,[deltay]
add [acc],ax
mov ax,[acc]
cmp ax,[deltax]
jb noincy
mov ax,[deltax]
sub [acc],ax
add di,[diry]
noincy:
callpt
jmp short lp1
ylp:
callpt
mov ax,[deltay]
mov [cnt],ax
lp2:
dec [cnt]
js done
add di,[diry]
mov ax,[deltax]
add [acc],ax
mov ax,[acc]
cmp ax,[deltay]
jb noincx
mov ax,[deltay]
sub [acc],ax
add si,[dirx]
noincx:
callpt
jmp short lp2
done: ret
bline endp

end