private void OnVisibilityChanged(OnVisibilityChangedEventArgs e)
 {
     if (OnVisibilityChangedEvent != null)
     {
         OnVisibilityChangedEvent(this, e);
     }
 }
            void DockableWindowsEvents_OnHide(
                DockableWindow DockableWindow,
                EventTimingEnum BeforeOrAfter,
                NameValueMap Context,
                out HandlingCodeEnum HandlingCode)
            {
                HandlingCode = HandlingCodeEnum.kEventNotHandled;

                if (DockableWindow == dockableWindow)
                {
                    OnVisibilityChangedEventArgs arg =
                        new OnVisibilityChangedEventArgs(
                            BeforeOrAfter,
                            false);

                    _form.OnVisibilityChanged(arg);

                    HandlingCode = arg.HandlingCode;
                }
            }