IDEAL
MODEL small
STACK 100h
DATASEG
; --------------------------
; Your variables here
; --------------------------

wid dw ?
hei dw ?
widr db ?
heir db ?
startd dw ?
startc dw ?
destx dw ?
desty dw ?
len dw ?

CODESEG
start:
    mov ax, @data
    mov ds, ax
; --------------------------
    mov ax, 0000h
    int 33h ; Enables mouse

    ;mov ax, 0002h
    ;int 33h

    mov ah, 00h
    mov al, 13h
    int 10h ;SETS GRAPHICS MODE

    mov al, 0fh
    xor cx, cx
    xor dx, dx
    loop1:
    pop di
    pop si
    push ax
    mov ax, 0003h
    int 33h
    pop ax
    shr cx, 1
    push cx
    push dx
    push bx
    and bx, 010b
    cmp bx, 010b
    je exit
    pop bx
    push bx
    and bx, 0100b
    cmp bx, 0100b
    jne cmpleft
    inc ax
    cmpleft:
    pop bx
    and bx, 01b
    cmp bx, 01b
    jne loop1
    call drawline
    jmp loop1

exit:
    mov ax, 4c00h
    int 21h

proc drawpix ;Draws a single pixel at point (cx,dx) of color = al
    mov ah, 0ch
    int 10h
    ret
endp drawpix

proc drawline ;Draws a line. Starting point (cx, dx) ending point (si,di)
    cmp si, cx
    jg startdrawline
    push si
    push cx
    pop si
    pop cx
    push di
    push dx
    pop di
    pop dx

    startdrawline:
    mov [destx], si
    mov [desty], di
    sub si, cx
    sub di, dx
    cmp si, 00h
    jne noflat
    call drawflatlinev
    jmp finishdrawline
    noflat:
    cmp di, 00h
    jne noflat2
    call drawflatlineh
    jmp finishdrawline
    noflat2:
    cmp si, di
    jl vert
    hor:
    call drawhorline
    jmp finishdrawline
    vert:
    call drawvertline

    finishdrawline:
    ret
endp drawline

proc drawhorline ; Draws horizontal line from (cx, dx) with x length si, y length di
    cmp di, 0
    mov bx, 1
    jg next1
    neg bx
    neg di

    next1:
    push ax
    mov ax, si
    push dx
    xor dx, dx
    div di
    mov si, ax
    mov [len], si
    pop dx
    pop ax

    drawh:
    call drawpix
    inc cx
    dec si
    cmp cx, [destx]
    je finishh
    cmp si, 0
    jge drawh
    mov si, [len]
    add dx, bx
    jmp drawh
    finishh:
    ret
endp drawhorline

proc drawvertline ; Draws vertical line from (cx, dx) with x length si, y length di
    cmp si, 0
    mov bx, 1
    jg next2
    neg bx
    neg si

    next2:
    push ax
    mov ax, di
    push dx
    xor dx, dx
    div si
    mov di, ax
    mov [len], di
    pop dx
    pop ax

    drawv:
    call drawpix
    inc dx
    dec di
    cmp dx, [desty]
    je finishv
    cmp di, 0
    jge drawv
    mov di, [len]
    add cx, bx
    jmp drawv
    finishv:
    ret
endp drawvertline

proc drawflatlineh
    drawfh:
    call drawpix
    inc cx
    cmp cx, [destx]
    jle drawfh
    ret
endp drawflatlineh

proc drawflatlinev
    drawfv:
    call drawpix
    inc dx
    cmp dx, [desty]
    jle drawfv
    ret
endp drawflatlinev

END start