program rajzolo;

uses newdelay,crt,graph;
type
   pont=record
    x:integer;
    y:integer;
    t:integer;
   end;
   tomb=array[1..4] of pont;
var a,b,c,d:integer;
    t:tomb;
    kf,ka,kj,kb:integer;
    x1,x2,y1,y2:integer;
    mp1,mp2,mp3,mp4:pont;
    x,y:integer;

function GraphInit:boolean;
var gd,gm:integer;
    utv:string;
begin
  utv:='';
  DetectGraph(gd,gm);
  {$I-}
  InitGraph(gd,gm,utv);
  while (GraphResult<>grOK) and (utv<>'exit') do
   begin
     {writeln('K‚rem az utvonalat a BGI filehoz vagy exit');}
     utv:='c:\aaa\tp\bgi';
     {readln(utv);}
     DetectGraph(gd,gm);
     Initgraph(gd,gm,utv);
   end;
  GraphInit:=(utv<>'exit');
  {$I+}
end;


procedure rajz(a,b,c,d:integer);
begin
line(a,c,b,c);
line(a,d,b,d);
line(a,c,a,d);
line(b,c,b,d);
end;



procedure egyenes(x1,y1,x2,y2:integer);

var t,x,y:integer;
begin
for t:=1 to 20 do
   begin
      x:=(1-t)*x1+t*x2;
      y:=(1-t)*y1+t*y2;
      putpixel(x,y,red);
   end;
end;

procedure metszespont1;
var x,y:integer;
    t:integer;

begin

x:=a;
t:=round((x1-x)/(x1-x2)); {t-re kifejezve  x:=(1-t)*x1+t*x2;}
y:=(1-t)*y1+t*y2;
mp1.x:=a;
mp1.y:=y;
mp1.t:=t;
end;


procedure metszespont2;
var x,y:integer;
    t:integer;

begin
y:=c;
t:=round((y1-y)/(y1-y2)); {t-re kifejezve  x:=(1-t)*x1+t*x2;}
x:=(1-t)*x1+t*x2;
mp2.x:=x;
mp2.y:=c;
mp2.t:=t;
end;




procedure metszespont3;
var x,y:integer;
    t:integer;

begin
y:=d;
t:=round((y1-y)/(y1-y2)); {t-re kifejezve  x:=(1-t)*x1+t*x2;}
x:=(1-t)*x1+t*x2;
mp3.x:=x;
mp3.y:=d;
mp3.t:=t;
end;


procedure metszespont4;
var x,y:integer;
    t:integer;

begin
x:=b;
t:=round((x1-x)/(x1-x2)); {t-re kifejezve  x:=(1-t)*x1+t*x2;}
y:=(1-t)*y1+t*y2;
mp4.x:=b;
mp4.y:=y;
mp4.t:=t;
end;

procedure tombfeltolt;
begin
t[1]:=mp1;
t[2]:=mp2;
t[3]:=mp3;
t[4]:=mp4;
end;

procedure csere(var a,b:pont);
var s:pont;
begin
s:=a;
a:=b;
b:=s;
end;


procedure rendez(var t:tomb;n:integer);
var i,j,min:integer;
begin
min:=1;
for i:=1 to n-1 do
   begin
   for j:=i+1 to n do
      if t[j].t<t[min].t then min:=j;
   csere(t[min],t[i]);
   end;
end;

procedure szakasz;
begin
if (x1<c) then
line(t[2].x,t[2].y,t[3].x,t[3].y)
end;


begin
if graphinit then
begin
a:=100;
b:=300;
c:=100;
d:=200;
rajz(a,b,c,d);
x1:=80;
y1:=80;
x2:=400;
y2:=300;
metszespont1;
metszespont2;
metszespont3;
metszespont4;
tombfeltolt;
rendez(t,4);
end;
repeat until keypressed;
end.