timer如何用的的

timer怎么用的的
procedure TForm2.Timer1Timer(Sender: TObject);
var
  Fullscreen:TBitmap;
  FullscreenC:TCanvas;
  dc:HDC;
begin
  Timer1.Enabled:=false;
  Fullscreen:=TBitmap.Create;
  Fullscreen.Width:=Screen.Width;
  Fullscreen.Height:=Screen.Height;
  DC:=GetDC(0);
  FullscreenC:=Tcanvas.Create;
  FullscreenC.Handle:=DC;
  Fullscreen.Canvas.CopyRect(Rect(0,0,Screen.Width,screen.Height),FullScreenC,
  rect(0,0,Screen.Width,screen.Height));
  FullscreenC.Free;
  ReleaseDC(0,DC);
  self.Image1.Picture.Bitmap:=Fullscreen;
  self.Image1.Width:=Fullscreen.Width;
  Self.Image1.Height:=FullScreen.Height;
  Fullscreen.Free;
  Form2.WindowState:=wsMaximized;
  Form2.Show;
  MessageBeep(1);
  foldx:=-1;
  foldy:=-1;
  self.Image1.Canvas.Pen.Mode:=pmNot;
  self.Image1.Canvas.Pen.Color:=clBlack;
  self.Image1.Canvas.Brush.Style:=BSCLEAR;
  flag:=true;
end;
  //能解释下么？？？

[解决办法]
假如Image1是放在一个Panel1（Panel1.Align是=alClient的）上的，而代码是这样子：

Delphi(Pascal) code

procedure TForm1.Image1MouseDown(Sender: TObject; Button: TMouseButton;  Shift: TShiftState; X, Y: Integer);begin  Form2.Canvas.MoveTo(foldx,foldy);  Form2.Canvas.LineTo(x,y);  foldx:=x;  foldy:=y;end;