Почему дочернее окно не выводится - Turbo Pascal

uses
  owindows, wintypes, winprocs;
 
type
  PControlPanel = ^TControlPanel;
  TControlPanel = object(TWindow)
 
  end;
 
type
  PGraphWindow = ^TGraphWindow;
  TGraphWindow = object(TWindow)
    panel: PControlPanel;
    constructor Init(parent_: PWindowsObject; title_: PChar);
    procedure WMLButtonDown(var msg: TMessage); virtual wm_first + wm_LButtonDown;
    procedure WMRButtonDown(var msg: TMessage); virtual wm_first + wm_RButtonDown;
  end;
 
constructor TGraphWindow.Init(parent_: PWindowsObject; title_: PChar);
begin
  inherited init(parent_, title_);
  panel := new(PControlPanel, init(@self, 'Control Panel'));
  panel^.show(sw_showNA);
end;
 
procedure TGraphWindow.WMLButtonDown(var msg: TMessage);
begin
  MessageBox(HWindow, 'You pressed left mouse button!', '', mb_ok);
end;
 
procedure TGraphWindow.WMRButtonDown(var msg: TMessage);
begin
  MessageBox(HWindow, 'You pressed right mouse button!', '', mb_ok);
end;
 
type
 
  TMyApp = object(TApplication)
    Procedure InitMainWindow; virtual;
  end;
 
procedure TMyApp.InitMainWindow;
begin
  mainwindow := new(PGraphWindow, init(nil, 'Graph editor'));
end;
 
var
  myapp: TMyApp;
begin
  myapp.init('Graph editor');
  myapp.run;
  myapp.done;
end.