unit Unit2;

interface

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

type
 TForm2 = class(TForm)
   Memo1: TMemo;
   Button2: TButton;
   Label1: TLabel;
   Edit1: TEdit;
   Timer1: TTimer;
   procedure Button2Click(Sender: TObject);
   procedure Timer1Timer(Sender: TObject);
 protected
   procedure CreateParams (var Params: TCreateparams); override;
 private
   { Private declarations }
 public
   { Public declarations }
 end;

var
 Form2: TForm2;

implementation

{$R *.dfm}

procedure TForm2.Button2Click(Sender: TObject);
begin
 Timer1.Enabled := True;
end;

procedure TForm2.CreateParams(var Params: TCreateparams);
begin
inherited;
Params.WindowClass.style := Params.WindowClass.style or CS_OWNDC;
end;

procedure TForm2.Timer1Timer(Sender: TObject);
const
 WindowName = 'Form2';
var
 //WindowRect: TRect;
 hWnd: THandle;
 bmp: TBitmap;
begin
 Beep;
 Timer1.Enabled := False;
 hWnd := FindWindow(nil, WindowName);
 //GetWindowRect(hWnd, WindowRect);

 bmp := TBitmap.Create;
 try
   bmp.Width := Width;
   bmp.Height := Height;
   StretchBlt(bmp.Canvas.Handle, 0, 0, Memo1.Width,
     Memo1.Height,
     GetDC(hWnd),
     0, 0, Memo1.Width,
     Memo1.Height, SRCCOPY);
   bmp.SaveToFile('test.bmp');
 finally
   bmp.Free;
 end;
end;

end.