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flat assembler > Examples and Tutorials > Another Draw Line rutine

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pabloreda



Joined: 24 Jan 2007
Posts: 89
Location: Argentina
I make a line draw with fixed point aproach, parameters in registers.

XRES is framebuffer width
SYSFRAME is framebuffer adress (32 bits color)
color is constant $ff00

Code:
;*******************************************
LINEA  ; eax=x1 ebx=y1 ecx=x2 edx=y2
        cmp ebx,edx
        je horizontal
        jg .noswap
        xchg eax,ecx
        xchg ebx,edx
.noswap
        shl eax,16
        shl ecx,16
        sub eax,ecx
        push ebx
        push edx
        sub ebx,edx
        add ebx,1
        cdq
        idiv ebx
        mov esi,eax
        add ecx,$7fff
        pop ebx
        pop edx
.lineas
        mov eax,ecx
        add eax,esi
        push ebx
        push eax
        shr ecx,16
        shr eax,16
        call horizontal
        pop ecx
        pop ebx
        add ebx,1
        cmp ebx,edx
        jle .lineas
        ret

horizontal  ; eax=x1 ebx=y1 ecx=x2
        cmp ecx,eax
        jg .m
        xchg ecx,eax
.m
        sub ecx,eax
        jnz .n
        add ecx,1
.n
        imul ebx,ebx,XRES
        add eax,ebx
        lea edi,SYSFRAME+eax*4
.l
        mov dword edi,$ff00
        add edi,4
        sub ecx,1
        jnz .l
        ret
    
Post 04 Oct 2013, 22:47
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macgub



Joined: 11 Jan 2006
Posts: 227
Location: Poland
Pablo, you implemented in assembler algo paining line using horizontal line drawing in inner loop. Nice.
I think instead:
Code:
.l
        mov dword edi,$ff00
        add edi,4
        sub ecx,1
        jnz .l
     

it can be:
Code:
       push eax
       mov  eax,$ff00
       cld
       rep   stosd   
       pop   eax
    
Post 15 Oct 2013, 06:48
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