three-conic-polygon-geometry/dist/three-conic-polygon-geometry.js

ThreeJS geometry for drawing polygons on a sphere

// Version 2.1.2 three-conic-polygon-geometry - https://github.com/vasturiano/three-conic-polygon-geometry
(function (global, factory) {
  typeof exports === 'object' && typeof module !== 'undefined' ? module.exports = factory(require('three')) :
  typeof define === 'function' && define.amd ? define(['three'], factory) :
  (global = typeof globalThis !== 'undefined' ? globalThis : global || self, global.ConicPolygonGeometry = factory(global.THREE));
})(this, (function (three) { 'use strict';

  function _arrayLikeToArray(r, a) {
    (null == a || a > r.length) && (a = r.length);
    for (var e = 0, n = Array(a); e < a; e++) n[e] = r[e];
    return n;
  }
  function _arrayWithHoles(r) {
    if (Array.isArray(r)) return r;
  }
  function _arrayWithoutHoles(r) {
    if (Array.isArray(r)) return _arrayLikeToArray(r);
  }
  function _assertThisInitialized(e) {
    if (undefined === e) throw new ReferenceError("this hasn't been initialised - super() hasn't been called");
    return e;
  }
  function _callSuper(t, o, e) {
    return o = _getPrototypeOf(o), _possibleConstructorReturn(t, _isNativeReflectConstruct() ? Reflect.construct(o, [], _getPrototypeOf(t).constructor) : o.apply(t, e));
  }
  function _classCallCheck(a, n) {
    if (!(a instanceof n)) throw new TypeError("Cannot call a class as a function");
  }
  function _createClass(e, r, t) {
    return Object.defineProperty(e, "prototype", {
      writable: false
    }), e;
  }
  function _getPrototypeOf(t) {
    return _getPrototypeOf = Object.setPrototypeOf ? Object.getPrototypeOf.bind() : function (t) {
      return t.__proto__ || Object.getPrototypeOf(t);
    }, _getPrototypeOf(t);
  }
  function _inherits(t, e) {
    if ("function" != typeof e && null !== e) throw new TypeError("Super expression must either be null or a function");
    t.prototype = Object.create(e && e.prototype, {
      constructor: {
        value: t,
        writable: true,
        configurable: true
      }
    }), Object.defineProperty(t, "prototype", {
      writable: false
    }), e && _setPrototypeOf(t, e);
  }
  function _isNativeReflectConstruct() {
    try {
      var t = !Boolean.prototype.valueOf.call(Reflect.construct(Boolean, [], function () {}));
    } catch (t) {}
    return (_isNativeReflectConstruct = function () {
      return !!t;
    })();
  }
  function _iterableToArray(r) {
    if ("undefined" != typeof Symbol && null != r[Symbol.iterator] || null != r["@@iterator"]) return Array.from(r);
  }
  function _iterableToArrayLimit(r, l) {
    var t = null == r ? null : "undefined" != typeof Symbol && r[Symbol.iterator] || r["@@iterator"];
    if (null != t) {
      var e,
        n,
        i,
        u,
        a = [],
        f = true,
        o = false;
      try {
        if (i = (t = t.call(r)).next, 0 === l) ; else for (; !(f = (e = i.call(t)).done) && (a.push(e.value), a.length !== l); f = !0);
      } catch (r) {
        o = true, n = r;
      } finally {
        try {
          if (!f && null != t.return && (u = t.return(), Object(u) !== u)) return;
        } finally {
          if (o) throw n;
        }
      }
      return a;
    }
  }
  function _nonIterableRest() {
    throw new TypeError("Invalid attempt to destructure non-iterable instance.\nIn order to be iterable, non-array objects must have a [Symbol.iterator]() method.");
  }
  function _nonIterableSpread() {
    throw new TypeError("Invalid attempt to spread non-iterable instance.\nIn order to be iterable, non-array objects must have a [Symbol.iterator]() method.");
  }
  function _possibleConstructorReturn(t, e) {
    if (e && ("object" == typeof e || "function" == typeof e)) return e;
    if (undefined !== e) throw new TypeError("Derived constructors may only return object or undefined");
    return _assertThisInitialized(t);
  }
  function _setPrototypeOf(t, e) {
    return _setPrototypeOf = Object.setPrototypeOf ? Object.setPrototypeOf.bind() : function (t, e) {
      return t.__proto__ = e, t;
    }, _setPrototypeOf(t, e);
  }
  function _slicedToArray(r, e) {
    return _arrayWithHoles(r) || _iterableToArrayLimit(r, e) || _unsupportedIterableToArray(r, e) || _nonIterableRest();
  }
  function _toConsumableArray(r) {
    return _arrayWithoutHoles(r) || _iterableToArray(r) || _unsupportedIterableToArray(r) || _nonIterableSpread();
  }
  function _unsupportedIterableToArray(r, a) {
    if (r) {
      if ("string" == typeof r) return _arrayLikeToArray(r, a);
      var t = {}.toString.call(r).slice(8, -1);
      return "Object" === t && r.constructor && (t = r.constructor.name), "Map" === t || "Set" === t ? Array.from(r) : "Arguments" === t || /^(?:Ui|I)nt(?:8|16|32)(?:Clamped)?Array$/.test(t) ? _arrayLikeToArray(r, a) : undefined;
    }
  }

  function ascending(a, b) {
    return a == null || b == null ? NaN : a < b ? -1 : a > b ? 1 : a >= b ? 0 : NaN;
  }

  function descending(a, b) {
    return a == null || b == null ? NaN
      : b < a ? -1
      : b > a ? 1
      : b >= a ? 0
      : NaN;
  }

  function bisector(f) {
    let compare1, compare2, delta;

    // If an accessor is specified, promote it to a comparator. In this case we
    // can test whether the search value is (self-) comparable. We can’t do this
    // for a comparator (except for specific, known comparators) because we can’t
    // tell if the comparator is symmetric, and an asymmetric comparator can’t be
    // used to test whether a single value is comparable.
    if (f.length !== 2) {
      compare1 = ascending;
      compare2 = (d, x) => ascending(f(d), x);
      delta = (d, x) => f(d) - x;
    } else {
      compare1 = f === ascending || f === descending ? f : zero$1;
      compare2 = f;
      delta = f;
    }

    function left(a, x, lo = 0, hi = a.length) {
      if (lo < hi) {
        if (compare1(x, x) !== 0) return hi;
        do {
          const mid = (lo + hi) >>> 1;
          if (compare2(a[mid], x) < 0) lo = mid + 1;
          else hi = mid;
        } while (lo < hi);
      }
      return lo;
    }

    function right(a, x, lo = 0, hi = a.length) {
      if (lo < hi) {
        if (compare1(x, x) !== 0) return hi;
        do {
          const mid = (lo + hi) >>> 1;
          if (compare2(a[mid], x) <= 0) lo = mid + 1;
          else hi = mid;
        } while (lo < hi);
      }
      return lo;
    }

    function center(a, x, lo = 0, hi = a.length) {
      const i = left(a, x, lo, hi - 1);
      return i > lo && delta(a[i - 1], x) > -delta(a[i], x) ? i - 1 : i;
    }

    return {left, center, right};
  }

  function zero$1() {
    return 0;
  }

  function number$1(x) {
    return x === null ? NaN : +x;
  }

  const ascendingBisect = bisector(ascending);
  const bisectRight = ascendingBisect.right;
  bisector(number$1).center;

  function extent(values, valueof) {
    let min;
    let max;
    if (valueof === undefined) {
      for (const value of values) {
        if (value != null) {
          if (min === undefined) {
            if (value >= value) min = max = value;
          } else {
            if (min > value) min = value;
            if (max < value) max = value;
          }
        }
      }
    } else {
      let index = -1;
      for (let value of values) {
        if ((value = valueof(value, ++index, values)) != null) {
          if (min === undefined) {
            if (value >= value) min = max = value;
          } else {
            if (min > value) min = value;
            if (max < value) max = value;
          }
        }
      }
    }
    return [min, max];
  }

  // https://github.com/python/cpython/blob/a74eea238f5baba15797e2e8b570d153bc8690a7/Modules/mathmodule.c#L1423
  class Adder {
    constructor() {
      this._partials = new Float64Array(32);
      this._n = 0;
    }
    add(x) {
      const p = this._partials;
      let i = 0;
      for (let j = 0; j < this._n && j < 32; j++) {
        const y = p[j],
          hi = x + y,
          lo = Math.abs(x) < Math.abs(y) ? x - (hi - y) : y - (hi - x);
        if (lo) p[i++] = lo;
        x = hi;
      }
      p[i] = x;
      this._n = i + 1;
      return this;
    }
    valueOf() {
      const p = this._partials;
      let n = this._n, x, y, lo, hi = 0;
      if (n > 0) {
        hi = p[--n];
        while (n > 0) {
          x = hi;
          y = p[--n];
          hi = x + y;
          lo = y - (hi - x);
          if (lo) break;
        }
        if (n > 0 && ((lo < 0 && p[n - 1] < 0) || (lo > 0 && p[n - 1] > 0))) {
          y = lo * 2;
          x = hi + y;
          if (y == x - hi) hi = x;
        }
      }
      return hi;
    }
  }

  const e10 = Math.sqrt(50),
      e5 = Math.sqrt(10),
      e2 = Math.sqrt(2);

  function tickSpec(start, stop, count) {
    const step = (stop - start) / Math.max(0, count),
        power = Math.floor(Math.log10(step)),
        error = step / Math.pow(10, power),
        factor = error >= e10 ? 10 : error >= e5 ? 5 : error >= e2 ? 2 : 1;
    let i1, i2, inc;
    if (power < 0) {
      inc = Math.pow(10, -power) / factor;
      i1 = Math.round(start * inc);
      i2 = Math.round(stop * inc);
      if (i1 / inc < start) ++i1;
      if (i2 / inc > stop) --i2;
      inc = -inc;
    } else {
      inc = Math.pow(10, power) * factor;
      i1 = Math.round(start / inc);
      i2 = Math.round(stop / inc);
      if (i1 * inc < start) ++i1;
      if (i2 * inc > stop) --i2;
    }
    if (i2 < i1 && 0.5 <= count && count < 2) return tickSpec(start, stop, count * 2);
    return [i1, i2, inc];
  }

  function ticks(start, stop, count) {
    stop = +stop, start = +start, count = +count;
    if (!(count > 0)) return [];
    if (start === stop) return [start];
    const reverse = stop < start, [i1, i2, inc] = reverse ? tickSpec(stop, start, count) : tickSpec(start, stop, count);
    if (!(i2 >= i1)) return [];
    const n = i2 - i1 + 1, ticks = new Array(n);
    if (reverse) {
      if (inc < 0) for (let i = 0; i < n; ++i) ticks[i] = (i2 - i) / -inc;
      else for (let i = 0; i < n; ++i) ticks[i] = (i2 - i) * inc;
    } else {
      if (inc < 0) for (let i = 0; i < n; ++i) ticks[i] = (i1 + i) / -inc;
      else for (let i = 0; i < n; ++i) ticks[i] = (i1 + i) * inc;
    }
    return ticks;
  }

  function tickIncrement(start, stop, count) {
    stop = +stop, start = +start, count = +count;
    return tickSpec(start, stop, count)[2];
  }

  function tickStep(start, stop, count) {
    stop = +stop, start = +start, count = +count;
    const reverse = stop < start, inc = reverse ? tickIncrement(stop, start, count) : tickIncrement(start, stop, count);
    return (reverse ? -1 : 1) * (inc < 0 ? 1 / -inc : inc);
  }

  function mean(values, valueof) {
    let count = 0;
    let sum = 0;
    if (valueof === undefined) {
      for (let value of values) {
        if (value != null && (value = +value) >= value) {
          ++count, sum += value;
        }
      }
    } else {
      let index = -1;
      for (let value of values) {
        if ((value = valueof(value, ++index, values)) != null && (value = +value) >= value) {
          ++count, sum += value;
        }
      }
    }
    if (count) return sum / count;
  }

  function* flatten$1(arrays) {
    for (const array of arrays) {
      yield* array;
    }
  }

  function merge(arrays) {
    return Array.from(flatten$1(arrays));
  }

  function earcut(data, holeIndices, dim = 2) {

      const hasHoles = holeIndices && holeIndices.length;
      const outerLen = hasHoles ? holeIndices[0] * dim : data.length;
      let outerNode = linkedList(data, 0, outerLen, dim, true);
      const triangles = [];

      if (!outerNode || outerNode.next === outerNode.prev) return triangles;

      let minX, minY, invSize;

      if (hasHoles) outerNode = eliminateHoles(data, holeIndices, outerNode, dim);

      // if the shape is not too simple, we'll use z-order curve hash later; calculate polygon bbox
      if (data.length > 80 * dim) {
          minX = Infinity;
          minY = Infinity;
          let maxX = -Infinity;
          let maxY = -Infinity;

          for (let i = dim; i < outerLen; i += dim) {
              const x = data[i];
              const y = data[i + 1];
              if (x < minX) minX = x;
              if (y < minY) minY = y;
              if (x > maxX) maxX = x;
              if (y > maxY) maxY = y;
          }

          // minX, minY and invSize are later used to transform coords into integers for z-order calculation
          invSize = Math.max(maxX - minX, maxY - minY);
          invSize = invSize !== 0 ? 32767 / invSize : 0;
      }

      earcutLinked(outerNode, triangles, dim, minX, minY, invSize, 0);

      return triangles;
  }

  // create a circular doubly linked list from polygon points in the specified winding order
  function linkedList(data, start, end, dim, clockwise) {
      let last;

      if (clockwise === (signedArea(data, start, end, dim) > 0)) {
          for (let i = start; i < end; i += dim) last = insertNode(i / dim | 0, data[i], data[i + 1], last);
      } else {
          for (let i = end - dim; i >= start; i -= dim) last = insertNode(i / dim | 0, data[i], data[i + 1], last);
      }

      if (last && equals(last, last.next)) {
          removeNode(last);
          last = last.next;
      }

      return last;
  }

  // eliminate colinear or duplicate points
  function filterPoints(start, end) {
      if (!start) return start;
      if (!end) end = start;

      let p = start,
          again;
      do {
          again = false;

          if (!p.steiner && (equals(p, p.next) || area(p.prev, p, p.next) === 0)) {
              removeNode(p);
              p = end = p.prev;
              if (p === p.next) break;
              again = true;

          } else {
              p = p.next;
          }
      } while (again || p !== end);

      return end;
  }

  // main ear slicing loop which triangulates a polygon (given as a linked list)
  function earcutLinked(ear, triangles, dim, minX, minY, invSize, pass) {
      if (!ear) return;

      // interlink polygon nodes in z-order
      if (!pass && invSize) indexCurve(ear, minX, minY, invSize);

      let stop = ear;

      // iterate through ears, slicing them one by one
      while (ear.prev !== ear.next) {
          const prev = ear.prev;
          const next = ear.next;

          if (invSize ? isEarHashed(ear, minX, minY, invSize) : isEar(ear)) {
              triangles.push(prev.i, ear.i, next.i); // cut off the triangle

              removeNode(ear);

              // skipping the next vertex leads to less sliver triangles
              ear = next.next;
              stop = next.next;

              continue;
          }

          ear = next;

          // if we looped through the whole remaining polygon and can't find any more ears
          if (ear === stop) {
              // try filtering points and slicing again
              if (!pass) {
                  earcutLinked(filterPoints(ear), triangles, dim, minX, minY, invSize, 1);

              // if this didn't work, try curing all small self-intersections locally
              } else if (pass === 1) {
                  ear = cureLocalIntersections(filterPoints(ear), triangles);
                  earcutLinked(ear, triangles, dim, minX, minY, invSize, 2);

              // as a last resort, try splitting the remaining polygon into two
              } else if (pass === 2) {
                  splitEarcut(ear, triangles, dim, minX, minY, invSize);
              }

              break;
          }
      }
  }

  // check whether a polygon node forms a valid ear with adjacent nodes
  function isEar(ear) {
      const a = ear.prev,
          b = ear,
          c = ear.next;

      if (area(a, b, c) >= 0) return false; // reflex, can't be an ear

      // now make sure we don't have other points inside the potential ear
      const ax = a.x, bx = b.x, cx = c.x, ay = a.y, by = b.y, cy = c.y;

      // triangle bbox
      const x0 = Math.min(ax, bx, cx),
          y0 = Math.min(ay, by, cy),
          x1 = Math.max(ax, bx, cx),
          y1 = Math.max(ay, by, cy);

      let p = c.next;
      while (p !== a) {
          if (p.x >= x0 && p.x <= x1 && p.y >= y0 && p.y <= y1 &&
              pointInTriangleExceptFirst(ax, ay, bx, by, cx, cy, p.x, p.y) &&
              area(p.prev, p, p.next) >= 0) return false;
          p = p.next;
      }

      return true;
  }

  function isEarHashed(ear, minX, minY, invSize) {
      const a = ear.prev,
          b = ear,
          c = ear.next;

      if (area(a, b, c) >= 0) return false; // reflex, can't be an ear

      const ax = a.x, bx = b.x, cx = c.x, ay = a.y, by = b.y, cy = c.y;

      // triangle bbox
      const x0 = Math.min(ax, bx, cx),
          y0 = Math.min(ay, by, cy),
          x1 = Math.max(ax, bx, cx),
          y1 = Math.max(ay, by, cy);

      // z-order range for the current triangle bbox;
      const minZ = zOrder(x0, y0, minX, minY, invSize),
          maxZ = zOrder(x1, y1, minX, minY, invSize);

      let p = ear.prevZ,
          n = ear.nextZ;

      // look for points inside the triangle in both directions
      while (p && p.z >= minZ && n && n.z <= maxZ) {
          if (p.x >= x0 && p.x <= x1 && p.y >= y0 && p.y <= y1 && p !== a && p !== c &&
              pointInTriangleExceptFirst(ax, ay, bx, by, cx, cy, p.x, p.y) && area(p.prev, p, p.next) >= 0) return false;
          p = p.prevZ;

          if (n.x >= x0 && n.x <= x1 && n.y >= y0 && n.y <= y1 && n !== a && n !== c &&
              pointInTriangleExceptFirst(ax, ay, bx, by, cx, cy, n.x, n.y) && area(n.prev, n, n.next) >= 0) return false;
          n = n.nextZ;
      }

      // look for remaining points in decreasing z-order
      while (p && p.z >= minZ) {
          if (p.x >= x0 && p.x <= x1 && p.y >= y0 && p.y <= y1 && p !== a && p !== c &&
              pointInTriangleExceptFirst(ax, ay, bx, by, cx, cy, p.x, p.y) && area(p.prev, p, p.next) >= 0) return false;
          p = p.prevZ;
      }

      // look for remaining points in increasing z-order
      while (n && n.z <= maxZ) {
          if (n.x >= x0 && n.x <= x1 && n.y >= y0 && n.y <= y1 && n !== a && n !== c &&
              pointInTriangleExceptFirst(ax, ay, bx, by, cx, cy, n.x, n.y) && area(n.prev, n, n.next) >= 0) return false;
          n = n.nextZ;
      }

      return true;
  }

  // go through all polygon nodes and cure small local self-intersections
  function cureLocalIntersections(start, triangles) {
      let p = start;
      do {
          const a = p.prev,
              b = p.next.next;

          if (!equals(a, b) && intersects(a, p, p.next, b) && locallyInside(a, b) && locallyInside(b, a)) {

              triangles.push(a.i, p.i, b.i);

              // remove two nodes involved
              removeNode(p);
              removeNode(p.next);

              p = start = b;
          }
          p = p.next;
      } while (p !== start);

      return filterPoints(p);
  }

  // try splitting polygon into two and triangulate them independently
  function splitEarcut(start, triangles, dim, minX, minY, invSize) {
      // look for a valid diagonal that divides the polygon into two
      let a = start;
      do {
          let b = a.next.next;
          while (b !== a.prev) {
              if (a.i !== b.i && isValidDiagonal(a, b)) {
                  // split the polygon in two by the diagonal
                  let c = splitPolygon(a, b);

                  // filter colinear points around the cuts
                  a = filterPoints(a, a.next);
                  c = filterPoints(c, c.next);

                  // run earcut on each half
                  earcutLinked(a, triangles, dim, minX, minY, invSize, 0);
                  earcutLinked(c, triangles, dim, minX, minY, invSize, 0);
                  return;
              }
              b = b.next;
          }
          a = a.next;
      } while (a !== start);
  }

  // link every hole into the outer loop, producing a single-ring polygon without holes
  function eliminateHoles(data, holeIndices, outerNode, dim) {
      const queue = [];

      for (let i = 0, len = holeIndices.length; i < len; i++) {
          const start = holeIndices[i] * dim;
          const end = i < len - 1 ? holeIndices[i + 1] * dim : data.length;
          const list = linkedList(data, start, end, dim, false);
          if (list === list.next) list.steiner = true;
          queue.push(getLeftmost(list));
      }

      queue.sort(compareXYSlope);

      // process holes from left to right
      for (let i = 0; i < queue.length; i++) {
          outerNode = eliminateHole(queue[i], outerNode);
      }

      return outerNode;
  }

  function compareXYSlope(a, b) {
      let result = a.x - b.x;
      // when the left-most point of 2 holes meet at a vertex, sort the holes counterclockwise so that when we find
      // the bridge to the outer shell is always the point that they meet at.
      if (result === 0) {
          result = a.y - b.y;
          if (result === 0) {
              const aSlope = (a.next.y - a.y) / (a.next.x - a.x);
              const bSlope = (b.next.y - b.y) / (b.next.x - b.x);
              result = aSlope - bSlope;
          }
      }
      return result;
  }

  // find a bridge between vertices that connects hole with an outer ring and and link it
  function eliminateHole(hole, outerNode) {
      const bridge = findHoleBridge(hole, outerNode);
      if (!bridge) {
          return outerNode;
      }

      const bridgeReverse = splitPolygon(bridge, hole);

      // filter collinear points around the cuts
      filterPoints(bridgeReverse, bridgeReverse.next);
      return filterPoints(bridge, bridge.next);
  }

  // David Eberly's algorithm for finding a bridge between hole and outer polygon
  function findHoleBridge(hole, outerNode) {
      let p = outerNode;
      const hx = hole.x;
      const hy = hole.y;
      let qx = -Infinity;
      let m;

      // find a segment intersected by a ray from the hole's leftmost point to the left;
      // segment's endpoint with lesser x will be potential connection point
      // unless they intersect at a vertex, then choose the vertex
      if (equals(hole, p)) return p;
      do {
          if (equals(hole, p.next)) return p.next;
          else if (hy <= p.y && hy >= p.next.y && p.next.y !== p.y) {
              const x = p.x + (hy - p.y) * (p.next.x - p.x) / (p.next.y - p.y);
              if (x <= hx && x > qx) {
                  qx = x;
                  m = p.x < p.next.x ? p : p.next;
                  if (x === hx) return m; // hole touches outer segment; pick leftmost endpoint
              }
          }
          p = p.next;
      } while (p !== outerNode);

      if (!m) return null;

      // look for points inside the triangle of hole point, segment intersection and endpoint;
      // if there are no points found, we have a valid connection;
      // otherwise choose the point of the minimum angle with the ray as connection point

      const stop = m;
      const mx = m.x;
      const my = m.y;
      let tanMin = Infinity;

      p = m;

      do {
          if (hx >= p.x && p.x >= mx && hx !== p.x &&
                  pointInTriangle(hy < my ? hx : qx, hy, mx, my, hy < my ? qx : hx, hy, p.x, p.y)) {

              const tan = Math.abs(hy - p.y) / (hx - p.x); // tangential

              if (locallyInside(p, hole) &&
                  (tan < tanMin || (tan === tanMin && (p.x > m.x || (p.x === m.x && sectorContainsSector(m, p)))))) {
                  m = p;
                  tanMin = tan;
              }
          }

          p = p.next;
      } while (p !== stop);

      return m;
  }

  // whether sector in vertex m contains sector in vertex p in the same coordinates
  function sectorContainsSector(m, p) {
      return area(m.prev, m, p.prev) < 0 && area(p.next, m, m.next) < 0;
  }

  // interlink polygon nodes in z-order
  function indexCurve(start, minX, minY, invSize) {
      let p = start;
      do {
          if (p.z === 0) p.z = zOrder(p.x, p.y, minX, minY, invSize);
          p.prevZ = p.prev;
          p.nextZ = p.next;
          p = p.next;
      } while (p !== start);

      p.prevZ.nextZ = null;
      p.prevZ = null;

      sortLinked(p);
  }

  // Simon Tatham's linked list merge sort algorithm
  // http://www.chiark.greenend.org.uk/~sgtatham/algorithms/listsort.html
  function sortLinked(list) {
      let numMerges;
      let inSize = 1;

      do {
          let p = list;
          let e;
          list = null;
          let tail = null;
          numMerges = 0;

          while (p) {
              numMerges++;
              let q = p;
              let pSize = 0;
              for (let i = 0; i < inSize; i++) {
                  pSize++;
                  q = q.nextZ;
                  if (!q) break;
              }
              let qSize = inSize;

              while (pSize > 0 || (qSize > 0 && q)) {

                  if (pSize !== 0 && (qSize === 0 || !q || p.z <= q.z)) {
                      e = p;
                      p = p.nextZ;
                      pSize--;
                  } else {
                      e = q;
                      q = q.nextZ;
                      qSize--;
                  }

                  if (tail) tail.nextZ = e;
                  else list = e;

                  e.prevZ = tail;
                  tail = e;
              }

              p = q;
          }

          tail.nextZ = null;
          inSize *= 2;

      } while (numMerges > 1);

      return list;
  }

  // z-order of a point given coords and inverse of the longer side of data bbox
  function zOrder(x, y, minX, minY, invSize) {
      // coords are transformed into non-negative 15-bit integer range
      x = (x - minX) * invSize | 0;
      y = (y - minY) * invSize | 0;

      x = (x | (x << 8)) & 0x00FF00FF;
      x = (x | (x << 4)) & 0x0F0F0F0F;
      x = (x | (x << 2)) & 0x33333333;
      x = (x | (x << 1)) & 0x55555555;

      y = (y | (y << 8)) & 0x00FF00FF;
      y = (y | (y << 4)) & 0x0F0F0F0F;
      y = (y | (y << 2)) & 0x33333333;
      y = (y | (y << 1)) & 0x55555555;

      return x | (y << 1);
  }

  // find the leftmost node of a polygon ring
  function getLeftmost(start) {
      let p = start,
          leftmost = start;
      do {
          if (p.x < leftmost.x || (p.x === leftmost.x && p.y < leftmost.y)) leftmost = p;
          p = p.next;
      } while (p !== start);

      return leftmost;
  }

  // check if a point lies within a convex triangle
  function pointInTriangle(ax, ay, bx, by, cx, cy, px, py) {
      return (cx - px) * (ay - py) >= (ax - px) * (cy - py) &&
             (ax - px) * (by - py) >= (bx - px) * (ay - py) &&
             (bx - px) * (cy - py) >= (cx - px) * (by - py);
  }

  // check if a point lies within a convex triangle but false if its equal to the first point of the triangle
  function pointInTriangleExceptFirst(ax, ay, bx, by, cx, cy, px, py) {
      return !(ax === px && ay === py) && pointInTriangle(ax, ay, bx, by, cx, cy, px, py);
  }

  // check if a diagonal between two polygon nodes is valid (lies in polygon interior)
  function isValidDiagonal(a, b) {
      return a.next.i !== b.i && a.prev.i !== b.i && !intersectsPolygon(a, b) && // dones't intersect other edges
             (locallyInside(a, b) && locallyInside(b, a) && middleInside(a, b) && // locally visible
              (area(a.prev, a, b.prev) || area(a, b.prev, b)) || // does not create opposite-facing sectors
              equals(a, b) && area(a.prev, a, a.next) > 0 && area(b.prev, b, b.next) > 0); // special zero-length case
  }

  // signed area of a triangle
  function area(p, q, r) {
      return (q.y - p.y) * (r.x - q.x) - (q.x - p.x) * (r.y - q.y);
  }

  // check if two points are equal
  function equals(p1, p2) {
      return p1.x === p2.x && p1.y === p2.y;
  }

  // check if two segments intersect
  function intersects(p1, q1, p2, q2) {
      const o1 = sign$2(area(p1, q1, p2));
      const o2 = sign$2(area(p1, q1, q2));
      const o3 = sign$2(area(p2, q2, p1));
      const o4 = sign$2(area(p2, q2, q1));

      if (o1 !== o2 && o3 !== o4) return true; // general case

      if (o1 === 0 && onSegment(p1, p2, q1)) return true; // p1, q1 and p2 are collinear and p2 lies on p1q1
      if (o2 === 0 && onSegment(p1, q2, q1)) return true; // p1, q1 and q2 are collinear and q2 lies on p1q1
      if (o3 === 0 && onSegment(p2, p1, q2)) return true; // p2, q2 and p1 are collinear and p1 lies on p2q2
      if (o4 === 0 && onSegment(p2, q1, q2)) return true; // p2, q2 and q1 are collinear and q1 lies on p2q2

      return false;
  }

  // for collinear points p, q, r, check if point q lies on segment pr
  function onSegment(p, q, r) {
      return q.x <= Math.max(p.x, r.x) && q.x >= Math.min(p.x, r.x) && q.y <= Math.max(p.y, r.y) && q.y >= Math.min(p.y, r.y);
  }

  function sign$2(num) {
      return num > 0 ? 1 : num < 0 ? -1 : 0;
  }

  // check if a polygon diagonal intersects any polygon segments
  function intersectsPolygon(a, b) {
      let p = a;
      do {
          if (p.i !== a.i && p.next.i !== a.i && p.i !== b.i && p.next.i !== b.i &&
                  intersects(p, p.next, a, b)) return true;
          p = p.next;
      } while (p !== a);

      return false;
  }

  // check if a polygon diagonal is locally inside the polygon
  function locallyInside(a, b) {
      return area(a.prev, a, a.next) < 0 ?
          area(a, b, a.next) >= 0 && area(a, a.prev, b) >= 0 :
          area(a, b, a.prev) < 0 || area(a, a.next, b) < 0;
  }

  // check if the middle point of a polygon diagonal is inside the polygon
  function middleInside(a, b) {
      let p = a;
      let inside = false;
      const px = (a.x + b.x) / 2;
      const py = (a.y + b.y) / 2;
      do {
          if (((p.y > py) !== (p.next.y > py)) && p.next.y !== p.y &&
                  (px < (p.next.x - p.x) * (py - p.y) / (p.next.y - p.y) + p.x))
              inside = !inside;
          p = p.next;
      } while (p !== a);

      return inside;
  }

  // link two polygon vertices with a bridge; if the vertices belong to the same ring, it splits polygon into two;
  // if one belongs to the outer ring and another to a hole, it merges it into a single ring
  function splitPolygon(a, b) {
      const a2 = createNode(a.i, a.x, a.y),
          b2 = createNode(b.i, b.x, b.y),
          an = a.next,
          bp = b.prev;

      a.next = b;
      b.prev = a;

      a2.next = an;
      an.prev = a2;

      b2.next = a2;
      a2.prev = b2;

      bp.next = b2;
      b2.prev = bp;

      return b2;
  }

  // create a node and optionally link it with previous one (in a circular doubly linked list)
  function insertNode(i, x, y, last) {
      const p = createNode(i, x, y);

      if (!last) {
          p.prev = p;
          p.next = p;

      } else {
          p.next = last.next;
          p.prev = last;
          last.next.prev = p;
          last.next = p;
      }
      return p;
  }

  function removeNode(p) {
      p.next.prev = p.prev;
      p.prev.next = p.next;

      if (p.prevZ) p.prevZ.nextZ = p.nextZ;
      if (p.nextZ) p.nextZ.prevZ = p.prevZ;
  }

  function createNode(i, x, y) {
      return {
          i, // vertex index in coordinates array
          x, y, // vertex coordinates
          prev: null, // previous and next vertex nodes in a polygon ring
          next: null,
          z: 0, // z-order curve value
          prevZ: null, // previous and next nodes in z-order
          nextZ: null,
          steiner: false // indicates whether this is a steiner point
      };
  }

  function signedArea(data, start, end, dim) {
      let sum = 0;
      for (let i = start, j = end - dim; i < end; i += dim) {
          sum += (data[j] - data[i]) * (data[i + 1] + data[j + 1]);
          j = i;
      }
      return sum;
  }

  // turn a polygon in a multi-dimensional array form (e.g. as in GeoJSON) into a form Earcut accepts
  function flatten(data) {
      const vertices = [];
      const holes = [];
      const dimensions = data[0][0].length;
      let holeIndex = 0;
      let prevLen = 0;

      for (const ring of data) {
          for (const p of ring) {
              for (let d = 0; d < dimensions; d++) vertices.push(p[d]);
          }
          if (prevLen) {
              holeIndex += prevLen;
              holes.push(holeIndex);
          }
          prevLen = ring.length;
      }
      return {vertices, holes, dimensions};
  }

  const epsilon$2 = 1.1102230246251565e-16;
  const splitter = 134217729;
  const resulterrbound = (3 + 8 * epsilon$2) * epsilon$2;

  // fast_expansion_sum_zeroelim routine from oritinal code
  function sum(elen, e, flen, f, h) {
      let Q, Qnew, hh, bvirt;
      let enow = e[0];
      let fnow = f[0];
      let eindex = 0;
      let findex = 0;
      if ((fnow > enow) === (fnow > -enow)) {
          Q = enow;
          enow = e[++eindex];
      } else {
          Q = fnow;
          fnow = f[++findex];
      }
      let hindex = 0;
      if (eindex < elen && findex < flen) {
          if ((fnow > enow) === (fnow > -enow)) {
              Qnew = enow + Q;
              hh = Q - (Qnew - enow);
              enow = e[++eindex];
          } else {
              Qnew = fnow + Q;
              hh = Q - (Qnew - fnow);
              fnow = f[++findex];
          }
          Q = Qnew;
          if (hh !== 0) {
              h[hindex++] = hh;
          }
          while (eindex < elen && findex < flen) {
              if ((fnow > enow) === (fnow > -enow)) {
                  Qnew = Q + enow;
                  bvirt = Qnew - Q;
                  hh = Q - (Qnew - bvirt) + (enow - bvirt);
                  enow = e[++eindex];
              } else {
                  Qnew = Q + fnow;
                  bvirt = Qnew - Q;
                  hh = Q - (Qnew - bvirt) + (fnow - bvirt);
                  fnow = f[++findex];
              }
              Q = Qnew;
              if (hh !== 0) {
                  h[hindex++] = hh;
              }
          }
      }
      while (eindex < elen) {
          Qnew = Q + enow;
          bvirt = Qnew - Q;
          hh = Q - (Qnew - bvirt) + (enow - bvirt);
          enow = e[++eindex];
          Q = Qnew;
          if (hh !== 0) {
              h[hindex++] = hh;
          }
      }
      while (findex < flen) {
          Qnew = Q + fnow;
          bvirt = Qnew - Q;
          hh = Q - (Qnew - bvirt) + (fnow - bvirt);
          fnow = f[++findex];
          Q = Qnew;
          if (hh !== 0) {
              h[hindex++] = hh;
          }
      }
      if (Q !== 0 || hindex === 0) {
          h[hindex++] = Q;
      }
      return hindex;
  }

  function estimate(elen, e) {
      let Q = e[0];
      for (let i = 1; i < elen; i++) Q += e[i];
      return Q;
  }

  function vec(n) {
      return new Float64Array(n);
  }

  const ccwerrboundA = (3 + 16 * epsilon$2) * epsilon$2;
  const ccwerrboundB = (2 + 12 * epsilon$2) * epsilon$2;
  const ccwerrboundC = (9 + 64 * epsilon$2) * epsilon$2 * epsilon$2;

  const B = vec(4);
  const C1 = vec(8);
  const C2 = vec(12);
  const D = vec(16);
  const u = vec(4);

  function orient2dadapt(ax, ay, bx, by, cx, cy, detsum) {
      let acxtail, acytail, bcxtail, bcytail;
      let bvirt, c, ahi, alo, bhi, blo, _i, _j, _0, s1, s0, t1, t0, u3;

      const acx = ax - cx;
      const bcx = bx - cx;
      const acy = ay - cy;
      const bcy = by - cy;

      s1 = acx * bcy;
      c = splitter * acx;
      ahi = c - (c - acx);
      alo = acx - ahi;
      c = splitter * bcy;
      bhi = c - (c - bcy);
      blo = bcy - bhi;
      s0 = alo * blo - (s1 - ahi * bhi - alo * bhi - ahi * blo);
      t1 = acy * bcx;
      c = splitter * acy;
      ahi = c - (c - acy);
      alo = acy - ahi;
      c = splitter * bcx;
      bhi = c - (c - bcx);
      blo = bcx - bhi;
      t0 = alo * blo - (t1 - ahi * bhi - alo * bhi - ahi * blo);
      _i = s0 - t0;
      bvirt = s0 - _i;
      B[0] = s0 - (_i + bvirt) + (bvirt - t0);
      _j = s1 + _i;
      bvirt = _j - s1;
      _0 = s1 - (_j - bvirt) + (_i - bvirt);
      _i = _0 - t1;
      bvirt = _0 - _i;
      B[1] = _0 - (_i + bvirt) + (bvirt - t1);
      u3 = _j + _i;
      bvirt = u3 - _j;
      B[2] = _j - (u3 - bvirt) + (_i - bvirt);
      B[3] = u3;

      let det = estimate(4, B);
      let errbound = ccwerrboundB * detsum;
      if (det >= errbound || -det >= errbound) {
          return det;
      }

      bvirt = ax - acx;
      acxtail = ax - (acx + bvirt) + (bvirt - cx);
      bvirt = bx - bcx;
      bcxtail = bx - (bcx + bvirt) + (bvirt - cx);
      bvirt = ay - acy;
      acytail = ay - (acy + bvirt) + (bvirt - cy);
      bvirt = by - bcy;
      bcytail = by - (bcy + bvirt) + (bvirt - cy);

      if (acxtail === 0 && acytail === 0 && bcxtail === 0 && bcytail === 0) {
          return det;
      }

      errbound = ccwerrboundC * detsum + resulterrbound * Math.abs(det);
      det += (acx * bcytail + bcy * acxtail) - (acy * bcxtail + bcx * acytail);
      if (det >= errbound || -det >= errbound) return det;

      s1 = acxtail * bcy;
      c = splitter * acxtail;
      ahi = c - (c - acxtail);
      alo = acxtail - ahi;
      c = splitter * bcy;
      bhi = c - (c - bcy);
      blo = bcy - bhi;
      s0 = alo * blo - (s1 - ahi * bhi - alo * bhi - ahi * blo);
      t1 = acytail * bcx;
      c = splitter * acytail;
      ahi = c - (c - acytail);
      alo = acytail - ahi;
      c = splitter * bcx;
      bhi = c - (c - bcx);
      blo = bcx - bhi;
      t0 = alo * blo - (t1 - ahi * bhi - alo * bhi - ahi * blo);
      _i = s0 - t0;
      bvirt = s0 - _i;
      u[0] = s0 - (_i + bvirt) + (bvirt - t0);
      _j = s1 + _i;
      bvirt = _j - s1;
      _0 = s1 - (_j - bvirt) + (_i - bvirt);
      _i = _0 - t1;
      bvirt = _0 - _i;
      u[1] = _0 - (_i + bvirt) + (bvirt - t1);
      u3 = _j + _i;
      bvirt = u3 - _j;
      u[2] = _j - (u3 - bvirt) + (_i - bvirt);
      u[3] = u3;
      const C1len = sum(4, B, 4, u, C1);

      s1 = acx * bcytail;
      c = splitter * acx;
      ahi = c - (c - acx);
      alo = acx - ahi;
      c = splitter * bcytail;
      bhi = c - (c - bcytail);
      blo = bcytail - bhi;
      s0 = alo * blo - (s1 - ahi * bhi - alo * bhi - ahi * blo);
      t1 = acy * bcxtail;
      c = splitter * acy;
      ahi = c - (c - acy);
      alo = acy - ahi;
      c = splitter * bcxtail;
      bhi = c - (c - bcxtail);
      blo = bcxtail - bhi;
      t0 = alo * blo - (t1 - ahi * bhi - alo * bhi - ahi * blo);
      _i = s0 - t0;
      bvirt = s0 - _i;
      u[0] = s0 - (_i + bvirt) + (bvirt - t0);
      _j = s1 + _i;
      bvirt = _j - s1;
      _0 = s1 - (_j - bvirt) + (_i - bvirt);
      _i = _0 - t1;
      bvirt = _0 - _i;
      u[1] = _0 - (_i + bvirt) + (bvirt - t1);
      u3 = _j + _i;
      bvirt = u3 - _j;
      u[2] = _j - (u3 - bvirt) + (_i - bvirt);
      u[3] = u3;
      const C2len = sum(C1len, C1, 4, u, C2);

      s1 = acxtail * bcytail;
      c = splitter * acxtail;
      ahi = c - (c - acxtail);
      alo = acxtail - ahi;
      c = splitter * bcytail;
      bhi = c - (c - bcytail);
      blo = bcytail - bhi;
      s0 = alo * blo - (s1 - ahi * bhi - alo * bhi - ahi * blo);
      t1 = acytail * bcxtail;
      c = splitter * acytail;
      ahi = c - (c - acytail);
      alo = acytail - ahi;
      c = splitter * bcxtail;
      bhi = c - (c - bcxtail);
      blo = bcxtail - bhi;
      t0 = alo * blo - (t1 - ahi * bhi - alo * bhi - ahi * blo);
      _i = s0 - t0;
      bvirt = s0 - _i;
      u[0] = s0 - (_i + bvirt) + (bvirt - t0);
      _j = s1 + _i;
      bvirt = _j - s1;
      _0 = s1 - (_j - bvirt) + (_i - bvirt);
      _i = _0 - t1;
      bvirt = _0 - _i;
      u[1] = _0 - (_i + bvirt) + (bvirt - t1);
      u3 = _j + _i;
      bvirt = u3 - _j;
      u[2] = _j - (u3 - bvirt) + (_i - bvirt);
      u[3] = u3;
      const Dlen = sum(C2len, C2, 4, u, D);

      return D[Dlen - 1];
  }

  function orient2d(ax, ay, bx, by, cx, cy) {
      const detleft = (ay - cy) * (bx - cx);
      const detright = (ax - cx) * (by - cy);
      const det = detleft - detright;

      const detsum = Math.abs(detleft + detright);
      if (Math.abs(det) >= ccwerrboundA * detsum) return det;

      return -orient2dadapt(ax, ay, bx, by, cx, cy, detsum);
  }

  const EPSILON = Math.pow(2, -52);
  const EDGE_STACK = new Uint32Array(512);

  class Delaunator {

      static from(points, getX = defaultGetX, getY = defaultGetY) {
          const n = points.length;
          const coords = new Float64Array(n * 2);

          for (let i = 0; i < n; i++) {
              const p = points[i];
              coords[2 * i] = getX(p);
              coords[2 * i + 1] = getY(p);
          }

          return new Delaunator(coords);
      }

      constructor(coords) {
          const n = coords.length >> 1;
          if (n > 0 && typeof coords[0] !== 'number') throw new Error('Expected coords to contain numbers.');

          this.coords = coords;

          // arrays that will store the triangulation graph
          const maxTriangles = Math.max(2 * n - 5, 0);
          this._triangles = new Uint32Array(maxTriangles * 3);
          this._halfedges = new Int32Array(maxTriangles * 3);

          // temporary arrays for tracking the edges of the advancing convex hull
          this._hashSize = Math.ceil(Math.sqrt(n));
          this._hullPrev = new Uint32Array(n); // edge to prev edge
          this._hullNext = new Uint32Array(n); // edge to next edge
          this._hullTri = new Uint32Array(n); // edge to adjacent triangle
          this._hullHash = new Int32Array(this._hashSize); // angular edge hash

          // temporary arrays for sorting points
          this._ids = new Uint32Array(n);
          this._dists = new Float64Array(n);

          this.update();
      }

      update() {
          const {coords, _hullPrev: hullPrev, _hullNext: hullNext, _hullTri: hullTri, _hullHash: hullHash} =  this;
          const n = coords.length >> 1;

          // populate an array of point indices; calculate input data bbox
          let minX = Infinity;
          let minY = Infinity;
          let maxX = -Infinity;
          let maxY = -Infinity;

          for (let i = 0; i < n; i++) {
              const x = coords[2 * i];
              const y = coords[2 * i + 1];
              if (x < minX) minX = x;
              if (y < minY) minY = y;
              if (x > maxX) maxX = x;
              if (y > maxY) maxY = y;
              this._ids[i] = i;
          }
          const cx = (minX + maxX) / 2;
          const cy = (minY + maxY) / 2;

          let i0, i1, i2;

          // pick a seed point close to the center
          for (let i = 0, minDist = Infinity; i < n; i++) {
              const d = dist(cx, cy, coords[2 * i], coords[2 * i + 1]);
              if (d < minDist) {
                  i0 = i;
                  minDist = d;
              }
          }
          const i0x = coords[2 * i0];
          const i0y = coords[2 * i0 + 1];

          // find the point closest to the seed
          for (let i = 0, minDist = Infinity; i < n; i++) {
              if (i === i0) continue;
              const d = dist(i0x, i0y, coords[2 * i], coords[2 * i + 1]);
              if (d < minDist && d > 0) {
                  i1 = i;
                  minDist = d;
              }
          }
          let i1x = coords[2 * i1];
          let i1y = coords[2 * i1 + 1];

          let minRadius = Infinity;

          // find the third point which forms the smallest circumcircle with the first two
          for (let i = 0; i < n; i++) {
              if (i === i0 || i === i1) continue;
              const r = circumradius(i0x, i0y, i1x, i1y, coords[2 * i], coords[2 * i + 1]);
              if (r < minRadius) {
                  i2 = i;
                  minRadius = r;
              }
          }
          let i2x = coords[2 * i2];
          let i2y = coords[2 * i2 + 1];

          if (minRadius === Infinity) {
              // order collinear points by dx (or dy if all x are identical)
              // and return the list as a hull
              for (let i = 0; i < n; i++) {
                  this._dists[i] = (coords[2 * i] - coords[0]) || (coords[2 * i + 1] - coords[1]);
              }
              quicksort(this._ids, this._dists, 0, n - 1);
              const hull = new Uint32Array(n);
              let j = 0;
              for (let i = 0, d0 = -Infinity; i < n; i++) {
                  const id = this._ids[i];
                  const d = this._dists[id];
                  if (d > d0) {
                      hull[j++] = id;
                      d0 = d;
                  }
              }
              this.hull = hull.subarray(0, j);
              this.triangles = new Uint32Array(0);
              this.halfedges = new Uint32Array(0);
              return;
          }

          // swap the order of the seed points for counter-clockwise orientation
          if (orient2d(i0x, i0y, i1x, i1y, i2x, i2y) < 0) {
              const i = i1;
              const x = i1x;
              const y = i1y;
              i1 = i2;
              i1x = i2x;
              i1y = i2y;
              i2 = i;
              i2x = x;
              i2y = y;
          }

          const center = circumcenter(i0x, i0y, i1x, i1y, i2x, i2y);
          this._cx = center.x;
          this._cy = center.y;

          for (let i = 0; i < n; i++) {
              this._dists[i] = dist(coords[2 * i], coords[2 * i + 1], center.x, center.y);
          }

          // sort the points by distance from the seed triangle circumcenter
          quicksort(this._ids, this._dists, 0, n - 1);

          // set up the seed triangle as the starting hull
          this._hullStart = i0;
          let hullSize = 3;

          hullNext[i0] = hullPrev[i2] = i1;
          hullNext[i1] = hullPrev[i0] = i2;
          hullNext[i2] = hullPrev[i1] = i0;

          hullTri[i0] = 0;
          hullTri[i1] = 1;
          hullTri[i2] = 2;

          hullHash.fill(-1);
          hullHash[this._hashKey(i0x, i0y)] = i0;
          hullHash[this._hashKey(i1x, i1y)] = i1;
          hullHash[this._hashKey(i2x, i2y)] = i2;

          this.trianglesLen = 0;
          this._addTriangle(i0, i1, i2, -1, -1, -1);

          for (let k = 0, xp, yp; k < this._ids.length; k++) {
              const i = this._ids[k];
              const x = coords[2 * i];
              const y = coords[2 * i + 1];

              // skip near-duplicate points
              if (k > 0 && Math.abs(x - xp) <= EPSILON && Math.abs(y - yp) <= EPSILON) continue;
              xp = x;
              yp = y;

              // skip seed triangle points
              if (i === i0 || i === i1 || i === i2) continue;

              // find a visible edge on the convex hull using edge hash
              let start = 0;
              for (let j = 0, key = this._hashKey(x, y); j < this._hashSize; j++) {
                  start = hullHash[(key + j) % this._hashSize];
                  if (start !== -1 && start !== hullNext[start]) break;
              }

              start = hullPrev[start];
              let e = start, q;
              while (q = hullNext[e], orient2d(x, y, coords[2 * e], coords[2 * e + 1], coords[2 * q], coords[2 * q + 1]) >= 0) {
                  e = q;
                  if (e === start) {
                      e = -1;
                      break;
                  }
              }
              if (e === -1) continue; // likely a near-duplicate point; skip it

              // add the first triangle from the point
              let t = this._addTriangle(e, i, hullNext[e], -1, -1, hullTri[e]);

              // recursively flip triangles from the point until they satisfy the Delaunay condition
              hullTri[i] = this._legalize(t + 2);
              hullTri[e] = t; // keep track of boundary triangles on the hull
              hullSize++;

              // walk forward through the hull, adding more triangles and flipping recursively
              let n = hullNext[e];
              while (q = hullNext[n], orient2d(x, y, coords[2 * n], coords[2 * n + 1], coords[2 * q], coords[2 * q + 1]) < 0) {
                  t = this._addTriangle(n, i, q, hullTri[i], -1, hullTri[n]);
                  hullTri[i] = this._legalize(t + 2);
                  hullNext[n] = n; // mark as removed
                  hullSize--;
                  n = q;
              }

              // walk backward from the other side, adding more triangles and flipping
              if (e === start) {
                  while (q = hullPrev[e], orient2d(x, y, coords[2 * q], coords[2 * q + 1], coords[2 * e], coords[2 * e + 1]) < 0) {
                      t = this._addTriangle(q, i, e, -1, hullTri[e], hullTri[q]);
                      this._legalize(t + 2);
                      hullTri[q] = t;
                      hullNext[e] = e; // mark as removed
                      hullSize--;
                      e = q;
                  }
              }

              // update the hull indices
              this._hullStart = hullPrev[i] = e;
              hullNext[e] = hullPrev[n] = i;
              hullNext[i] = n;

              // save the two new edges in the hash table
              hullHash[this._hashKey(x, y)] = i;
              hullHash[this._hashKey(coords[2 * e], coords[2 * e + 1])] = e;
          }

          this.hull = new Uint32Array(hullSize);
          for (let i = 0, e = this._hullStart; i < hullSize; i++) {
              this.hull[i] = e;
              e = hullNext[e];
          }

          // trim typed triangle mesh arrays
          this.triangles = this._triangles.subarray(0, this.trianglesLen);
          this.halfedges = this._halfedges.subarray(0, this.trianglesLen);
      }

      _hashKey(x, y) {
          return Math.floor(pseudoAngle(x - this._cx, y - this._cy) * this._hashSize) % this._hashSize;
      }

      _legalize(a) {
          const {_triangles: triangles, _halfedges: halfedges, coords} = this;

          let i = 0;
          let ar = 0;

          // recursion eliminated with a fixed-size stack
          w