//--------------------------------------------------------------------------------------------------

        void EnsureMarker()
        {
            if (_Marker == null)
            {
                _Marker = new AIS_Point(new Geom_CartesianPoint(0, 0, 0));
                _Marker.SetMarker(Aspect_TypeOfMarker.Aspect_TOM_PLUS);
                _Marker.SetWidth(2.0);
                WorkspaceController.Workspace.AisContext.Display(_Marker, false);
                WorkspaceController.Workspace.AisContext.Deactivate(_Marker);
            }
        }