QDockWidget custom titlebar removes focus of application

Hi,
I have a custom titlebar in a custom QDockWidget to have a better undock behavior and possibilities.
All works good, the only problem is when I init one QMainWindow with dock inside, the focus of the QMainWindow is removed.
Here the code of my custom QDockWidget :

Code:

---

CDockWidget::CDockWidget( const QString& Title, QWidget* Parent ) :
QDockWidget( Title, Parent )
{
  m_Titlebar = new CTitlebarWidget( this );
  setTitleBarWidget( m_Titlebar );
}
 
bool CDockWidget::event( QEvent* event )
{
  switch( event->type() )
  {
    case QEvent::WindowTitleChange :
    {
      m_Titlebar->SetTitle( windowTitle() );
      return true;
    }
 
    case QEvent::NonClientAreaMouseButtonDblClick :
    {
      if( isMaximized() )
        showNormal();
      else
        showMaximized();
      return true;
    }
  }
  return QDockWidget::event( event );
}

---

If I comment the constructor code and the switch in the event function, the focus is not removed.
How can I solve this problem ?
Thanks for the help