dwg_get_entity_layer (const Dwg_Object_Entity *ent)
{
  // TODO: empty means default layer 0
  return ent->layer ? ent->layer->obj->tio.object->tio.LAYER : NULL;
}
dwg_get_entity_layer (const Dwg_Object_Entity *ent)
{
   
  return ent->layer ? ent->layer->obj->tio.object->tio.LAYER : NULL;
}