procedure ChangeAppWindow(const Handle: THandle; const SetAppWindow, RestoreVisibility: Boolean);

var

  Style: Integer;

  WasVisible, WasIconic: Boolean;

begin

  Style := GetWindowLong(Handle, GWL_EXSTYLE);

  if (SetAppWindow and (Style and WS_EX_APPWINDOW = 0)) or (not SetAppWindow and (Style and WS_EX_APPWINDOW = WS_EX_APPWINDOW)) then

  begin

    WasVisible := IsWindowVisible(Handle);

    if WasVisible or WasIconic then

    begin

      ShowWindow(Handle, SW_HIDE);

    end

    else

    begin

        ShowWindow(Handle, SW_SHOW);

    end;

  end;

end;

procedure TForm1.Button1Click(Sender: TObject);

begin

   ChangeAppWindow(form1.Handle, False, False);

end;

procedure TForm1.Button2Click(Sender: TObject);

begin

  ChangeAppWindow(form1.Handle, True, True);

end;