Движение квадрата по диагонали. (canvas)

unit Unit1;
 
interface
 
uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, ExtCtrls,math, StdCtrls;
 
type
  TForm1 = class(TForm)
    Timer1: TTimer;
    procedure FormPaint(Sender: TObject);
    procedure FormKeyPress(Sender: TObject; var Key: Char);
    procedure Timer1Timer(Sender: TObject);
    function Dotr(x1,y1,x2,y2:integer): real;
    procedure FormCreate(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;
 
var
  Form1: TForm1;
  n,dl:Integer;
  x1,x2,y1,y2:Integer;
 
implementation
 
{$R *.dfm}
 
function TForm1.Dotr(x1,y1,x2,y2:integer): real;  //возвращает длинну отрезка
begin
result:=sqrt(sqr(x2-x1)+sqr(y2-y1));
end;
 
procedure TForm1.FormPaint(Sender: TObject);
begin
  Canvas.MoveTo(0,0);
  Canvas.LineTo(ClientWidth,ClientHeight);
   Canvas.Pen.Color:=clBlack;
   Canvas.Brush.Color:=clBlack;
   Canvas.Rectangle(x1,y1,x2,y2);
end;
 
procedure TForm1.FormKeyPress(Sender: TObject; var Key: Char);
begin
    if Key=#13 then
    begin
      if n=0 then
        begin
          Canvas.Rectangle(x1,y1,x2,y2);
          Canvas.Pen.Color:=clRed;
          Canvas.Brush.Color:=clRed;
          n:=1;
        end
      else
        begin
          Canvas.Rectangle(x1,y1,x2,y2);
          Canvas.Pen.Color:=clBlack;
          Canvas.Brush.Color:=clBlack;
          n:=0;
        end;
    end;
end;
 
procedure TForm1.Timer1Timer(Sender: TObject);
var ugol:real;
begin
ugol:=ArcCos((sqr(ClientWidth)+sqr(Dotr(0,0,ClientHeight,ClientWidth))-sqr(ClientHeight))/(2*Dotr(0,0,ClientHeight,ClientWidth)*ClientWidth));
x1:=round(dl*cos(ugol));
y1:=round(dl*sin(ugol));
x2:=x1+100;
y2:=y1+100;
inc(dl,5);
Repaint;
end;
 
procedure TForm1.FormCreate(Sender: TObject);
begin
   x1:=0; x2:=100;
   y1:=0; y2:=100;
end;
 
end.

unit Unit1;
 
interface
 
uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, ExtCtrls;
 
type
  TForm1 = class(TForm)
    Timer1: TTimer;
    Timer2: TTimer;
    procedure Timer1Timer(Sender: TObject);
    procedure FormCreate(Sender: TObject);
    procedure Timer2Timer(Sender: TObject);
    procedure FormKeyPress(Sender: TObject; var Key: Char);
  private
    { Private-Deklarationen }
  public
    { Public-Deklarationen }
  end;
 
var
  Form1: TForm1;
  x,y: Integer;
  w, h: Integer;
  n: Integer;
  Col: TColor = clGreen;
implementation
 
{$R *.dfm}
 
procedure TForm1.FormCreate(Sender: TObject);
begin
  w := 50;
  h := 50;
end;
 
procedure TForm1.FormKeyPress(Sender: TObject; var Key: Char);
begin
  if Key = #13 then
    begin
      if n = 0 then
        begin
          Col := clRed;
           n := 1;
        end
      else
        begin
          Col := clGreen;
          n := 0;
        end;
    end;
end;
 
procedure TForm1.Timer1Timer(Sender: TObject);
begin
  Repaint;
  Canvas.Rectangle(x, y, x + w, y + h);
  Canvas.Pen.Color := Col;
  Canvas.Brush.Color := Col;
  x := x + 1;
  y := y + 1;
  if (x + w > ClientWidth) or (y + w > ClientHeight) then
    begin
      Timer1.Enabled := False;
      Timer2.Enabled := True;
    end;
end;
 
procedure TForm1.Timer2Timer(Sender: TObject);
begin
  Repaint;
  Canvas.Rectangle(x, y, x + w, y + h);
  Canvas.Pen.Color := Col;
  Canvas.Brush.Color := Col;
  x := x - 1;
  y := y - 1;
  if (x  <= 0) or (y <= 0) then
    begin
      Timer2.Enabled := False;
      Timer1.Enabled := True;
    end;
end;
 
end.

procedure TForm1.Timer1Timer(Sender: TObject);
var
  ugol:real;
begin
  ugol:=ArcCos((sqr(ClientWidth)+sqr(Dotr(0,0,ClientHeight,ClientWidth))-sqr(ClientHeight))/(2*Dotr(0,0,ClientHeight,ClientWidth)*ClientWidth));
  if (x1+70>=ClientWidth)or(y1+70>=ClientHeight)then
    flag:=true;
  if (x1<=0)or(y1<=0)then
    flag:=false;
  x1:=round(dl*cos(ugol));
  y1:=round(dl*sin(ugol));
  x2:=x1+70;
  y2:=y1+70;
  if flag then
    dec(dl,5)
  else
    inc(dl,5);
 
  Repaint;
end;