Function IsValidClosedPath

3rdparty/clipper2/src/clipper.engine.cpp:449–453

  }

  inline bool IsValidClosedPath(const OutPt* op)
  {
    return op && (op->next != op) && (op->next != op->prev) &&
      !IsVerySmallTriangle(*op);
  }

  inline bool OutrecIsAscending(const Active* hotEdge)
  {