Создание линии без использования Line

uses graphABC;
//процедура рисования отрезка
procedure Brezenhem(x1,y1,x2,y2:integer);
var currentX, currentY: integer;
    errorX, errorY: integer;
    d, dx, dy, incX, incY: integer;
begin
dx := x2 - x1;
dy := y2 - y1;
errorX := 0;
errorY := 0;
if(dx > 0) then incX := 1
else if(dx = 0) then incX := 0
else incX := -1;
if(dy > 0) then incY := 1
else if(dy = 0) then incY := 0
else incY := -1;
dx := abs(dx);
dy := abs(dy);
if(dy > dx) then d := dy
else d := dx;
currentX := x1;
currentY := y1;
setpixel(currentX, currentY, clRed);
while((currentX <> x2) OR (currentY <> y2)) do
 begin
  errorX := errorX + dx;
  errorY := errorY + dy;
  if(errorX >= d) then
   begin
    errorX := errorX - d;
    currentX := currentX + incX;
   end;
  if(errorY >= d) then
   begin
    errorY := errorY - d;
    currentY := currentY + incY;
   end;
  SetPixel(currentX, currentY, clRed);
 end;
end;
 
var x1,y1,x2,y2,i,x3,x4,y3,y4,d:integer;
begin
setwindowsize(600,400);
centerwindow;
d:=5;
x1:=windowwidth div 2-d*50;
y1:=windowheight div 2-d*30;
x2:=windowwidth div 2+d*50;
y2:=windowheight div 2+d*30;
x3:=x1;
x4:=x3+d;
while x3<x2 do
 begin
  Brezenhem(x3,y1,x4,y1);
  Brezenhem(x3,y2,x4,y2);
  x3:=x3+2*d;
  x4:=x3+d;
 end;
y3:=y1;
y4:=y3+d;
while y3<y2 do
 begin
  Brezenhem(x1,y3,x1,y4);
  Brezenhem(x2,y3,x2,y4);
  y3:=y3+2*d;
  y4:=y3+d;
 end;
end.