select

  bool selected(k3d::face* face)  {   if (face->visible_selection)    return true;   k3d::split_edge* edge = face->first_edge;   do {    if (edge->visible_selection || edge->vertex->visible_selection || (edge->companion && (edge->companion->visible_selection || edge->companion->vertex->visible_selection)))     return true;   } while (edge != face->first_edge);   return false;  }