[Dublin]

Код:

unit MainUnit;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, ExtCtrls;

type
     TKasat = class
      StartX, StartY:Integer;
      A1,B1,C1,D,x11,x22:extended;
       xn1,xn2,yn1,yn2:variant;
      procedure DKasat;

  end;

  TEllipse = class
    StartX, StartY:Integer;
    procedure DEllipse;
    procedure Erase;
  end;
  TAnimation = Class
   Ellipse : TEllipse;
   Kasat : TKasat;

  End;
  TForm1 = class(TForm)
    PB1: TPaintBox;
    procedure FormClick(Sender: TObject);
    procedure FormCreate(Sender: TObject);
    procedure FormMouseMove(Sender: TObject; Shift: TShiftState; X,
      Y: Integer);
    procedure FormDbClick(Sender: TObject);

  private
    { Private declarations }
    OldPenMode:TPenMode;
    StartX, StartY, OldX, OldY:Integer;
    dragging:Boolean;
  public
    { Public declarations }
  end;
const
x1=0;
y1=0;

var
  Form1: TForm1;
    Picture : TAnimation;
implementation

{$R *.dfm}



procedure TForm1.FormCreate(Sender: TObject);
begin
 dragging:=false;
end;

procedure TEllipse.DEllipse;
begin
with Form1.PB1.Canvas do begin
 Pen.Color:=clWhite;
 Ellipse(StartX-140, StartY-140,StartX+140, StartY+140 );
 end;
 end;

Procedure TKasat.DKasat;
begin
 A1:=sqr(x1)-2*x1*startx+sqr(startx)+sqr(y1)-2*y1*starty+sqr(starty);
  B1:=2*sqr(140)*startx-2*sqr(140)*x1-2*sqr(x1)*startx+4*x1*sqr(startx)-2*sqr(startx)*startx-2*sqr(y1)*startx+4*y1*starty*startx-2*startx*sqr(starty);
  C1:=sqr(140*140)+2*sqr(140)*x1*startx-2*sqr(140)*sqr(startx)+sqr(x1)*sqr(startx)-2*sqr(startx)*startx*x1+sqr(startx*startx)-sqr(140)*sqr(y1)+sqr(y1)*sqr(startx)+2*y1*starty*sqr(140)-2*y1*starty*sqr(startx)-sqr(140)*sqr(starty)+sqr(startx*starty);
  D:=sqr(B1)-4*A1*C1;
  x11:=sqrt(abs(D))-B1;
  x22:=-B1-sqrt(abs(D));
  xn1:=x11/(2*A1);
  xn2:=x22/(2*A1);
 yn1:=starty+(sqr(140)-(xn1-startx)*(x1-startx))/(y1-starty);
  yn2:=starty+(sqr(140)-(xn2-startx)*(x1-startx))/(y1-starty);
with Form1.PB1.Canvas do begin
   Polyline([Point(x1,y1),Point(xn1,yn1)]);
   Polyline([Point(xn1,yn1),Point(xn2,yn2)]);
   Polyline([Point(x1,y1),Point(xn2,yn2)]);
   end;
   end;

procedure TEllipse.Erase;
begin
with Form1.PB1.Canvas do begin
   Brush.Color:=clBlack;
   Rectangle(0, 0,800, 800 );
   Pen.Color:=clBlack;
   Rectangle(0, 0,800, 800 );
 end;
 end;

procedure TForm1.FormClick(Sender: TObject);
begin
 dragging:=true;
end;

procedure TForm1.FormMouseMove(Sender: TObject; Shift: TShiftState; X,
  Y: Integer);
var    a,b,t: integer;
 Xn1,Xn2,Yn1,Yn2:variant;
 A1,B1,C1,D,x11,x22,y11,y22,E:extended;
  begin
 StartX:=X;
 StartY:=Y;
 if dragging=false then exit;
with Picture do
 begin
 Ellipse.Erase;
 Ellipse.DEllipse;
 Kasat.DKasat;
 end;
end;

procedure TForm1.FormDbClick(Sender: TObject);
begin
 dragging:=false;
end;

end.