private static void OLDexpandHull(
      PtEntry convHullEntry, PtEntry aHull, PtEntry bHull, boolean ccw) {
    boolean db__OLD = C.vb(DB_HULLEXPAND);
    if (db__OLD && T.update()) T.msg("expandHull" + T.show(convHullEntry) + " ccw=" + ccw);

    PtEntry[] opp = new PtEntry[2];
    opp[0] = aHull;
    opp[1] = bHull;

    PtEntry old____hEnt = convHullEntry;
    boolean advanced = false;
    do {
      if (old____hEnt != convHullEntry) advanced = true;
      inf.update();
      if (old____hEnt.source() == null) {
        if (db__OLD && T.update())
          T.msg("expandHull, source unknown, guaranteed not convex" + T.show(old____hEnt));
        old____hEnt = old____hEnt.next(ccw);
        continue;
      }

      int w = (old____hEnt.source() == opp[0].source()) ? 1 : 0;
      PtEntry oppEnt = opp[w];

      boolean isTangent =
          !COper3.right(old____hEnt, oppEnt, oppEnt.next(true), ccw)
              && !COper3.right(old____hEnt, oppEnt, oppEnt.prev(true), ccw);

      if (!isTangent) {
        if (db__OLD && T.update())
          T.msg(
              "expandHull, advance tangent line"
                  + T.show(oppEnt.toPolygon(), MyColor.cDARKGRAY, -1, MARK_X)
                  + T.show(old____hEnt)
                  + tl(old____hEnt, oppEnt));
        opp[w] = oppEnt.next(ccw);
        continue;
      }

      if (COper3.left(old____hEnt, oppEnt, old____hEnt.next(ccw), ccw)
          && COper3.left(old____hEnt, oppEnt, old____hEnt.prev(ccw), ccw)) {
        DArray dispPts = new DArray();

        // delete points until cross tangent line
        PtEntry next = old____hEnt.next(ccw);
        while (true) {
          PtEntry prev = next;
          dispPts.add(prev);
          next = prev.delete(ccw);

          inf.update();
          if (COper3.right(old____hEnt, oppEnt, next, ccw)) {
            FPoint2 cross = MyMath.linesIntersection(old____hEnt, oppEnt, prev, next, null);
            old____hEnt = old____hEnt.insert(new PtEntry(cross), ccw);
            if (db__OLD && T.update())
              T.msg(
                  "expandHull, clipped to shadow region"
                      + tl(old____hEnt, oppEnt)
                      + T.show(old____hEnt)
                      + T.show(dispPts));
            break;
          }
        }
      } else {
        if (db__OLD && T.update())
          T.msg(
              "expandHull, not dipping into shadow region"
                  + T.show(old____hEnt.next(ccw))
                  + tl(old____hEnt, oppEnt));
      }
      old____hEnt = old____hEnt.next(ccw);
    } while (!advanced || old____hEnt != convHullEntry);
  }
  /**
   * Apply hull expansion procedure
   *
   * @param convHullEntry an entry of the hull (should be on the convex hull, so it is not deleted
   *     or replaced and is still valid for subsequent calls)
   * @param aHull entry on convex hull of polygon A
   * @param bHull entry on convex hull of polygon B
   * @param ccw true to move in ccw direction, else cw
   */
  private static void expandHull(PtEntry convHullEntry, PtEntry aHull, PtEntry bHull, boolean ccw) {
    if (C.vb(OLDMETHOD)) {
      OLDexpandHull(convHullEntry, aHull, bHull, ccw);
      return;
    }
    boolean db = C.vb(DB_HULLEXPAND);

    if (db && T.update()) T.msg("expandHull" + T.show(convHullEntry) + " ccw=" + ccw);

    // tangent points for A, B
    PtEntry[] tangentPoints = new PtEntry[2];
    tangentPoints[0] = aHull;
    tangentPoints[1] = bHull;

    PtEntry hEnt = convHullEntry;
    do {
      inf.update();

      // calculate tangent ray R
      PtEntry tangentPt = null;
      while (true) {
        int tanIndex = (hEnt.source() == tangentPoints[0].source()) ? 1 : 0;
        tangentPt = tangentPoints[tanIndex];

        if (!COper3.right(hEnt, tangentPt, tangentPt.next(true), ccw)
            && !COper3.right(hEnt, tangentPt, tangentPt.prev(true), ccw)) break;

        tangentPt = tangentPt.next(ccw);

        if (db && T.update())
          T.msg(
              "expandHull, advance tangent line"
                  + T.show(tangentPt.toPolygon(), MyColor.cDARKGRAY, -1, MARK_DISC)
                  + T.show(hEnt)
                  + tl(hEnt, tangentPt));
        tangentPoints[tanIndex] = tangentPt;
      }

      if (COper3.left(hEnt, tangentPt, hEnt.next(ccw), ccw)) {
        DArray dispPts = new DArray();

        // delete points until cross tangent line
        PtEntry next = hEnt.next(ccw);
        while (true) {
          PtEntry prev = next;
          dispPts.add(prev);
          next = prev.delete(ccw);
          if (COper3.right(hEnt, tangentPt, next, ccw)) {
            FPoint2 cross = MyMath.linesIntersection(hEnt, tangentPt, prev, next, null);
            hEnt = hEnt.insert(new PtEntry(cross), ccw);
            if (db && T.update())
              T.msg(
                  "expandHull, clipped to shadow region"
                      + tl(hEnt, tangentPt)
                      + T.show(hEnt)
                      + T.show(dispPts));
            break;
          }
        }
      } else {
        if (db && T.update())
          T.msg(
              "expandHull, not dipping into shadow region"
                  + T.show(hEnt.next(ccw))
                  + tl(hEnt, tangentPt));
      }
      while (true) {
        hEnt = hEnt.next(ccw);
        if (COper3.left(hEnt.prev(ccw), hEnt, hEnt.next(ccw), ccw)) break;
        if (db && T.update()) T.msg("skipping reflex vertex" + T.show(hEnt));
      }
    } while (hEnt != convHullEntry);
  }