public void HookUp(object rcwPresenter)
        {
            _pvpPresenter = (IPvpPresenter)rcwPresenter;

            CompositionTarget.Rendering += CompositionTarget_Rendering;
            _hookedUp = true;
        }
        public void Dispose()
        {
            _pvpPresenter = null; // it's released when the renderer is finalized
            if (_hookedUp)
            {
                CompositionTarget.Rendering -= CompositionTarget_Rendering;
            }

            _hookedUp = false;
        }