TEmulatorThread = class(TThread)
private
  FOwnerHandle: THandle;
protected
  procedure Execute; override;
  property OwnerHandle: THandle read FOwnerHandle;
public
  constructor Create(OwnerHandle: THandle);
end;

constructor TEmulatorThread.Create(OwnerHandle: THandle);
begin
  FOwnerHandle := OwnerHandle;
  inherited Create(False);
end;

procedure TEmulatorThread.Execute;
var
  msg: TMsg;
begin
  with TDataBus.Create(OwnerHandle) do
  try
    while not Terminated do
    begin
      try
        while PeekMessage(msg, 0, 0, 0, PM_REMOVE) do
          if msg.message = WM_TERMINATE then
            Terminate
          else
            DispatchMessage(msg);
        if not Terminated then
          WaitMessage;
      except
        PostMessage(OwnerHandle, WM_EXCEPTION, Integer(AcquireExceptionObject), 0);
      end;
    end;
  finally
    Free;
  end;
end;

constructor TEmulator.Create;
begin
  inherited;
  FDataBus := nil;
  FWindowHandle := AllocateHWnd(WindowProc);
  FThread := TEmulatorThread.Create(FWindowHandle);
end;

destructor TEmulator.Destroy;
begin
  PostThreadMessage(FThread.ThreadID, WM_TERMINATE, 0, 0);
  FThread.WaitFor;
  FThread.Free;
  DeallocateHWnd(FWindowHandle);
  inherited;
end;

procedure TEmulator.WindowProc(var Message: TMessage);
begin
  with Message do
    case msg of
      WM_DATABUS_NOTIFY:
        case WParam of
          DB_CREATED:
            FDataBus := TDataBus(LParam);
          DB_DESTROYING:
            FDataBus := nil;
          DB_OBJECT_ADDED:
            ;
          DB_OBJECT_DELETED:
            ;
        end;
      WM_OBJECT_NOTIFY:
        ;
      WM_EXCEPTION:
        begin
          raise Exception(WParam);
        end;
    else
      DefWindowProc(FWindowHandle, msg, WParam, LParam);
    end;
end;

procedure TBONDataBus.AfterConstruction;
begin
  PostMessage(FOwnerHandle, WM_DATABUS_NOTIFY, DB_CREATED, Integer(Self));
end;

procedure TBONDataBus.BeforeDestruction;
begin
  PostMessage(FOwnerHandle, WM_DATABUS_NOTIFY, DB_DESTROYING, 0);
  inherited;
end;