Просмотр буфера обмена 2

...
private
  { Private declarations }
  PrevHwnd: Hwnd;

  procedure WMChangeCBChain(var Msg: TWMChangeCBChain);
    message WM_CHANGECBCHAIN;

  procedure WMDrawClipboard(var Msg: TWMDrawClipboard);
    message WM_DRAWCLIPBOARD;
...

procedure TForm1.WMChangeCBChain(var Msg: TWMChangeCBChain);
begin
  if PrevHWnd = Msg.Remove then
    PrevHWnd := Msg.Next;
  if Msg.Remove <> Handle then
    SendMessage(PrevHWnd, WM_CHANGECBCHAIN, Msg.Remove, Msg.Next);
end;

procedure TForm1.WMDrawClipboard(var Msg: TWMDrawClipboard);
var
  P: PChar;
  H: THandle;
begin
  SendMessage(PrevHWnd, WM_DRAWCLIPBOARD, 0, 0);
  if Clipboard.HasFormat(CF_TEXT) then
  begin
    H := Clipboard.GetAsHandle(CF_TEXT);
    Len := GlobalSize(H) + 1;
    P := GlobalLock(H);
    Memo1.SetTextBuf(P);
    GlobalUnlock(H);
  end;
  Msg.Result := 0;
end;

procedure TForm1.FormCreate(Sender: TObject);
begin
  PrevHwnd := SetClipboardViewer(Handle);
end;

procedure TForm1.FormDestroy(Sender: TObject);
begin
  ChangeClipboardChain(Handle, PrevHwnd);
end;