refactor: move everything into src/ subdirectory

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diff --git a/modules/3rdparty/rhill-voronoi-core.js b/modules/3rdparty/rhill-voronoi-core.js
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--- a/modules/3rdparty/rhill-voronoi-core.js
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@@ -1,1723 +0,0 @@
-/*!
-Copyright (C) 2010-2013 Raymond Hill: https://github.com/gorhill/Javascript-Voronoi
-MIT License: See https://github.com/gorhill/Javascript-Voronoi/LICENSE.md
-*/
-/*
-Author: Raymond Hill (rhill@raymondhill.net)
-Contributor: Jesse Morgan (morgajel@gmail.com)
-File: rhill-voronoi-core.js
-Version: 0.98
-Date: January 21, 2013
-Description: This is my personal Javascript implementation of
-Steven Fortune's algorithm to compute Voronoi diagrams.
-
-License: See https://github.com/gorhill/Javascript-Voronoi/LICENSE.md
-Credits: See https://github.com/gorhill/Javascript-Voronoi/CREDITS.md
-History: See https://github.com/gorhill/Javascript-Voronoi/CHANGELOG.md
-
-## Usage:
-
-  var sites = [{x:300,y:300}, {x:100,y:100}, {x:200,y:500}, {x:250,y:450}, {x:600,y:150}];
-  // xl, xr means x left, x right
-  // yt, yb means y top, y bottom
-  var bbox = {xl:0, xr:800, yt:0, yb:600};
-  var voronoi = new Voronoi();
-  // pass an object which exhibits xl, xr, yt, yb properties. The bounding
-  // box will be used to connect unbound edges, and to close open cells
-  result = voronoi.compute(sites, bbox);
-  // render, further analyze, etc.
-
-Return value:
-  An object with the following properties:
-
-  result.vertices = an array of unordered, unique Voronoi.Vertex objects making
-    up the Voronoi diagram.
-  result.edges = an array of unordered, unique Voronoi.Edge objects making up
-    the Voronoi diagram.
-  result.cells = an array of Voronoi.Cell object making up the Voronoi diagram.
-    A Cell object might have an empty array of halfedges, meaning no Voronoi
-    cell could be computed for a particular cell.
-  result.execTime = the time it took to compute the Voronoi diagram, in
-    milliseconds.
-
-Voronoi.Vertex object:
-  x: The x position of the vertex.
-  y: The y position of the vertex.
-
-Voronoi.Edge object:
-  lSite: the Voronoi site object at the left of this Voronoi.Edge object.
-  rSite: the Voronoi site object at the right of this Voronoi.Edge object (can
-    be null).
-  va: an object with an 'x' and a 'y' property defining the start point
-    (relative to the Voronoi site on the left) of this Voronoi.Edge object.
-  vb: an object with an 'x' and a 'y' property defining the end point
-    (relative to Voronoi site on the left) of this Voronoi.Edge object.
-
-  For edges which are used to close open cells (using the supplied bounding
-  box), the rSite property will be null.
-
-Voronoi.Cell object:
-  site: the Voronoi site object associated with the Voronoi cell.
-  halfedges: an array of Voronoi.Halfedge objects, ordered counterclockwise,
-    defining the polygon for this Voronoi cell.
-
-Voronoi.Halfedge object:
-  site: the Voronoi site object owning this Voronoi.Halfedge object.
-  edge: a reference to the unique Voronoi.Edge object underlying this
-    Voronoi.Halfedge object.
-  getStartpoint(): a method returning an object with an 'x' and a 'y' property
-    for the start point of this halfedge. Keep in mind halfedges are always
-    countercockwise.
-  getEndpoint(): a method returning an object with an 'x' and a 'y' property
-    for the end point of this halfedge. Keep in mind halfedges are always
-    countercockwise.
-
-TODO: Identify opportunities for performance improvement.
-
-TODO: Let the user close the Voronoi cells, do not do it automatically. Not only let
-      him close the cells, but also allow him to close more than once using a different
-      bounding box for the same Voronoi diagram.
-*/
-
-/*global Math */
-
-// ---------------------------------------------------------------------------
-
-function Voronoi() {
-    this.vertices = null;
-    this.edges = null;
-    this.cells = null;
-    this.toRecycle = null;
-    this.beachsectionJunkyard = [];
-    this.circleEventJunkyard = [];
-    this.vertexJunkyard = [];
-    this.edgeJunkyard = [];
-    this.cellJunkyard = [];
-    }
-
-// ---------------------------------------------------------------------------
-
-Voronoi.prototype.reset = function() {
-    if (!this.beachline) {
-        this.beachline = new this.RBTree();
-        }
-    // Move leftover beachsections to the beachsection junkyard.
-    if (this.beachline.root) {
-        var beachsection = this.beachline.getFirst(this.beachline.root);
-        while (beachsection) {
-            this.beachsectionJunkyard.push(beachsection); // mark for reuse
-            beachsection = beachsection.rbNext;
-            }
-        }
-    this.beachline.root = null;
-    if (!this.circleEvents) {
-        this.circleEvents = new this.RBTree();
-        }
-    this.circleEvents.root = this.firstCircleEvent = null;
-    this.vertices = [];
-    this.edges = [];
-    this.cells = [];
-    };
-
-Voronoi.prototype.sqrt = Math.sqrt;
-Voronoi.prototype.abs = Math.abs;
-Voronoi.prototype.ε = Voronoi.ε = 1e-9;
-Voronoi.prototype.invε = Voronoi.invε = 1.0 / Voronoi.ε;
-Voronoi.prototype.equalWithEpsilon = function(a,b){return this.abs(a-b)<1e-9;};
-Voronoi.prototype.greaterThanWithEpsilon = function(a,b){return a-b>1e-9;};
-Voronoi.prototype.greaterThanOrEqualWithEpsilon = function(a,b){return b-a<1e-9;};
-Voronoi.prototype.lessThanWithEpsilon = function(a,b){return b-a>1e-9;};
-Voronoi.prototype.lessThanOrEqualWithEpsilon = function(a,b){return a-b<1e-9;};
-
-// ---------------------------------------------------------------------------
-// Red-Black tree code (based on C version of "rbtree" by Franck Bui-Huu
-// https://github.com/fbuihuu/libtree/blob/master/rb.c
-
-Voronoi.prototype.RBTree = function() {
-    this.root = null;
-    };
-
-Voronoi.prototype.RBTree.prototype.rbInsertSuccessor = function(node, successor) {
-    var parent;
-    if (node) {
-        // >>> rhill 2011-05-27: Performance: cache previous/next nodes
-        successor.rbPrevious = node;
-        successor.rbNext = node.rbNext;
-        if (node.rbNext) {
-            node.rbNext.rbPrevious = successor;
-            }
-        node.rbNext = successor;
-        // <<<
-        if (node.rbRight) {
-            // in-place expansion of node.rbRight.getFirst();
-            node = node.rbRight;
-            while (node.rbLeft) {node = node.rbLeft;}
-            node.rbLeft = successor;
-            }
-        else {
-            node.rbRight = successor;
-            }
-        parent = node;
-        }
-    // rhill 2011-06-07: if node is null, successor must be inserted
-    // to the left-most part of the tree
-    else if (this.root) {
-        node = this.getFirst(this.root);
-        // >>> Performance: cache previous/next nodes
-        successor.rbPrevious = null;
-        successor.rbNext = node;
-        node.rbPrevious = successor;
-        // <<<
-        node.rbLeft = successor;
-        parent = node;
-        }
-    else {
-        // >>> Performance: cache previous/next nodes
-        successor.rbPrevious = successor.rbNext = null;
-        // <<<
-        this.root = successor;
-        parent = null;
-        }
-    successor.rbLeft = successor.rbRight = null;
-    successor.rbParent = parent;
-    successor.rbRed = true;
-    // Fixup the modified tree by recoloring nodes and performing
-    // rotations (2 at most) hence the red-black tree properties are
-    // preserved.
-    var grandpa, uncle;
-    node = successor;
-    while (parent && parent.rbRed) {
-        grandpa = parent.rbParent;
-        if (parent === grandpa.rbLeft) {
-            uncle = grandpa.rbRight;
-            if (uncle && uncle.rbRed) {
-                parent.rbRed = uncle.rbRed = false;
-                grandpa.rbRed = true;
-                node = grandpa;
-                }
-            else {
-                if (node === parent.rbRight) {
-                    this.rbRotateLeft(parent);
-                    node = parent;
-                    parent = node.rbParent;
-                    }
-                parent.rbRed = false;
-                grandpa.rbRed = true;
-                this.rbRotateRight(grandpa);
-                }
-            }
-        else {
-            uncle = grandpa.rbLeft;
-            if (uncle && uncle.rbRed) {
-                parent.rbRed = uncle.rbRed = false;
-                grandpa.rbRed = true;
-                node = grandpa;
-                }
-            else {
-                if (node === parent.rbLeft) {
-                    this.rbRotateRight(parent);
-                    node = parent;
-                    parent = node.rbParent;
-                    }
-                parent.rbRed = false;
-                grandpa.rbRed = true;
-                this.rbRotateLeft(grandpa);
-                }
-            }
-        parent = node.rbParent;
-        }
-    this.root.rbRed = false;
-    };
-
-Voronoi.prototype.RBTree.prototype.rbRemoveNode = function(node) {
-    // >>> rhill 2011-05-27: Performance: cache previous/next nodes
-    if (node.rbNext) {
-        node.rbNext.rbPrevious = node.rbPrevious;
-        }
-    if (node.rbPrevious) {
-        node.rbPrevious.rbNext = node.rbNext;
-        }
-    node.rbNext = node.rbPrevious = null;
-    // <<<
-    var parent = node.rbParent,
-        left = node.rbLeft,
-        right = node.rbRight,
-        next;
-    if (!left) {
-        next = right;
-        }
-    else if (!right) {
-        next = left;
-        }
-    else {
-        next = this.getFirst(right);
-        }
-    if (parent) {
-        if (parent.rbLeft === node) {
-            parent.rbLeft = next;
-            }
-        else {
-            parent.rbRight = next;
-            }
-        }
-    else {
-        this.root = next;
-        }
-    // enforce red-black rules
-    var isRed;
-    if (left && right) {
-        isRed = next.rbRed;
-        next.rbRed = node.rbRed;
-        next.rbLeft = left;
-        left.rbParent = next;
-        if (next !== right) {
-            parent = next.rbParent;
-            next.rbParent = node.rbParent;
-            node = next.rbRight;
-            parent.rbLeft = node;
-            next.rbRight = right;
-            right.rbParent = next;
-            }
-        else {
-            next.rbParent = parent;
-            parent = next;
-            node = next.rbRight;
-            }
-        }
-    else {
-        isRed = node.rbRed;
-        node = next;
-        }
-    // 'node' is now the sole successor's child and 'parent' its
-    // new parent (since the successor can have been moved)
-    if (node) {
-        node.rbParent = parent;
-        }
-    // the 'easy' cases
-    if (isRed) {return;}
-    if (node && node.rbRed) {
-        node.rbRed = false;
-        return;
-        }
-    // the other cases
-    var sibling;
-    do {
-        if (node === this.root) {
-            break;
-            }
-        if (node === parent.rbLeft) {
-            sibling = parent.rbRight;
-            if (sibling.rbRed) {
-                sibling.rbRed = false;
-                parent.rbRed = true;
-                this.rbRotateLeft(parent);
-                sibling = parent.rbRight;
-                }
-            if ((sibling.rbLeft && sibling.rbLeft.rbRed) || (sibling.rbRight && sibling.rbRight.rbRed)) {
-                if (!sibling.rbRight || !sibling.rbRight.rbRed) {
-                    sibling.rbLeft.rbRed = false;
-                    sibling.rbRed = true;
-                    this.rbRotateRight(sibling);
-                    sibling = parent.rbRight;
-                    }
-                sibling.rbRed = parent.rbRed;
-                parent.rbRed = sibling.rbRight.rbRed = false;
-                this.rbRotateLeft(parent);
-                node = this.root;
-                break;
-                }
-            }
-        else {
-            sibling = parent.rbLeft;
-            if (sibling.rbRed) {
-                sibling.rbRed = false;
-                parent.rbRed = true;
-                this.rbRotateRight(parent);
-                sibling = parent.rbLeft;
-                }
-            if ((sibling.rbLeft && sibling.rbLeft.rbRed) || (sibling.rbRight && sibling.rbRight.rbRed)) {
-                if (!sibling.rbLeft || !sibling.rbLeft.rbRed) {
-                    sibling.rbRight.rbRed = false;
-                    sibling.rbRed = true;
-                    this.rbRotateLeft(sibling);
-                    sibling = parent.rbLeft;
-                    }
-                sibling.rbRed = parent.rbRed;
-                parent.rbRed = sibling.rbLeft.rbRed = false;
-                this.rbRotateRight(parent);
-                node = this.root;
-                break;
-                }
-            }
-        sibling.rbRed = true;
-        node = parent;
-        parent = parent.rbParent;
-    } while (!node.rbRed);
-    if (node) {node.rbRed = false;}
-    };
-
-Voronoi.prototype.RBTree.prototype.rbRotateLeft = function(node) {
-    var p = node,
-        q = node.rbRight, // can't be null
-        parent = p.rbParent;
-    if (parent) {
-        if (parent.rbLeft === p) {
-            parent.rbLeft = q;
-            }
-        else {
-            parent.rbRight = q;
-            }
-        }
-    else {
-        this.root = q;
-        }
-    q.rbParent = parent;
-    p.rbParent = q;
-    p.rbRight = q.rbLeft;
-    if (p.rbRight) {
-        p.rbRight.rbParent = p;
-        }
-    q.rbLeft = p;
-    };
-
-Voronoi.prototype.RBTree.prototype.rbRotateRight = function(node) {
-    var p = node,
-        q = node.rbLeft, // can't be null
-        parent = p.rbParent;
-    if (parent) {
-        if (parent.rbLeft === p) {
-            parent.rbLeft = q;
-            }
-        else {
-            parent.rbRight = q;
-            }
-        }
-    else {
-        this.root = q;
-        }
-    q.rbParent = parent;
-    p.rbParent = q;
-    p.rbLeft = q.rbRight;
-    if (p.rbLeft) {
-        p.rbLeft.rbParent = p;
-        }
-    q.rbRight = p;
-    };
-
-Voronoi.prototype.RBTree.prototype.getFirst = function(node) {
-    while (node.rbLeft) {
-        node = node.rbLeft;
-        }
-    return node;
-    };
-
-Voronoi.prototype.RBTree.prototype.getLast = function(node) {
-    while (node.rbRight) {
-        node = node.rbRight;
-        }
-    return node;
-    };
-
-// ---------------------------------------------------------------------------
-// Diagram methods
-
-Voronoi.prototype.Diagram = function(site) {
-    this.site = site;
-    };
-
-// ---------------------------------------------------------------------------
-// Cell methods
-
-Voronoi.prototype.Cell = function(site) {
-    this.site = site;
-    this.halfedges = [];
-    this.closeMe = false;
-    };
-
-Voronoi.prototype.Cell.prototype.init = function(site) {
-    this.site = site;
-    this.halfedges = [];
-    this.closeMe = false;
-    return this;
-    };
-
-Voronoi.prototype.createCell = function(site) {
-    var cell = this.cellJunkyard.pop();
-    if ( cell ) {
-        return cell.init(site);
-        }
-    return new this.Cell(site);
-    };
-
-Voronoi.prototype.Cell.prototype.prepareHalfedges = function() {
-    var halfedges = this.halfedges,
-        iHalfedge = halfedges.length,
-        edge;
-    // get rid of unused halfedges
-    // rhill 2011-05-27: Keep it simple, no point here in trying
-    // to be fancy: dangling edges are a typically a minority.
-    while (iHalfedge--) {
-        edge = halfedges[iHalfedge].edge;
-        if (!edge.vb || !edge.va) {
-            halfedges.splice(iHalfedge,1);
-            }
-        }
-
-    // rhill 2011-05-26: I tried to use a binary search at insertion
-    // time to keep the array sorted on-the-fly (in Cell.addHalfedge()).
-    // There was no real benefits in doing so, performance on
-    // Firefox 3.6 was improved marginally, while performance on
-    // Opera 11 was penalized marginally.
-    halfedges.sort(function(a,b){return b.angle-a.angle;});
-    return halfedges.length;
-    };
-
-// Return a list of the neighbor Ids
-Voronoi.prototype.Cell.prototype.getNeighborIds = function() {
-    var neighbors = [],
-        iHalfedge = this.halfedges.length,
-        edge;
-    while (iHalfedge--){
-        edge = this.halfedges[iHalfedge].edge;
-        if (edge.lSite !== null && edge.lSite.voronoiId != this.site.voronoiId) {
-            neighbors.push(edge.lSite.voronoiId);
-            }
-        else if (edge.rSite !== null && edge.rSite.voronoiId != this.site.voronoiId){
-            neighbors.push(edge.rSite.voronoiId);
-            }
-        }
-    return neighbors;
-    };
-
-// Compute bounding box
-//
-Voronoi.prototype.Cell.prototype.getBbox = function() {
-    var halfedges = this.halfedges,
-        iHalfedge = halfedges.length,
-        xmin = Infinity,
-        ymin = Infinity,
-        xmax = -Infinity,
-        ymax = -Infinity,
-        v, vx, vy;
-    while (iHalfedge--) {
-        v = halfedges[iHalfedge].getStartpoint();
-        vx = v.x;
-        vy = v.y;
-        if (vx < xmin) {xmin = vx;}
-        if (vy < ymin) {ymin = vy;}
-        if (vx > xmax) {xmax = vx;}
-        if (vy > ymax) {ymax = vy;}
-        // we dont need to take into account end point,
-        // since each end point matches a start point
-        }
-    return {
-        x: xmin,
-        y: ymin,
-        width: xmax-xmin,
-        height: ymax-ymin
-        };
-    };
-
-// Return whether a point is inside, on, or outside the cell:
-//   -1: point is outside the perimeter of the cell
-//    0: point is on the perimeter of the cell
-//    1: point is inside the perimeter of the cell
-//
-Voronoi.prototype.Cell.prototype.pointIntersection = function(x, y) {
-    // Check if point in polygon. Since all polygons of a Voronoi
-    // diagram are convex, then:
-    // http://paulbourke.net/geometry/polygonmesh/
-    // Solution 3 (2D):
-    //   "If the polygon is convex then one can consider the polygon
-    //   "as a 'path' from the first vertex. A point is on the interior
-    //   "of this polygons if it is always on the same side of all the
-    //   "line segments making up the path. ...
-    //   "(y - y0) (x1 - x0) - (x - x0) (y1 - y0)
-    //   "if it is less than 0 then P is to the right of the line segment,
-    //   "if greater than 0 it is to the left, if equal to 0 then it lies
-    //   "on the line segment"
-    var halfedges = this.halfedges,
-        iHalfedge = halfedges.length,
-        halfedge,
-        p0, p1, r;
-    while (iHalfedge--) {
-        halfedge = halfedges[iHalfedge];
-        p0 = halfedge.getStartpoint();
-        p1 = halfedge.getEndpoint();
-        r = (y-p0.y)*(p1.x-p0.x)-(x-p0.x)*(p1.y-p0.y);
-        if (!r) {
-            return 0;
-            }
-        if (r > 0) {
-            return -1;
-            }
-        }
-    return 1;
-    };
-
-// ---------------------------------------------------------------------------
-// Edge methods
-//
-
-Voronoi.prototype.Vertex = function(x, y) {
-    this.x = x;
-    this.y = y;
-    };
-
-Voronoi.prototype.Edge = function(lSite, rSite) {
-    this.lSite = lSite;
-    this.rSite = rSite;
-    this.va = this.vb = null;
-    };
-
-Voronoi.prototype.Halfedge = function(edge, lSite, rSite) {
-    this.site = lSite;
-    this.edge = edge;
-    // 'angle' is a value to be used for properly sorting the
-    // halfsegments counterclockwise. By convention, we will
-    // use the angle of the line defined by the 'site to the left'
-    // to the 'site to the right'.
-    // However, border edges have no 'site to the right': thus we
-    // use the angle of line perpendicular to the halfsegment (the
-    // edge should have both end points defined in such case.)
-    if (rSite) {
-        this.angle = Math.atan2(rSite.y-lSite.y, rSite.x-lSite.x);
-        }
-    else {
-        var va = edge.va,
-            vb = edge.vb;
-        // rhill 2011-05-31: used to call getStartpoint()/getEndpoint(),
-        // but for performance purpose, these are expanded in place here.
-        this.angle = edge.lSite === lSite ?
-            Math.atan2(vb.x-va.x, va.y-vb.y) :
-            Math.atan2(va.x-vb.x, vb.y-va.y);
-        }
-    };
-
-Voronoi.prototype.createHalfedge = function(edge, lSite, rSite) {
-    return new this.Halfedge(edge, lSite, rSite);
-    };
-
-Voronoi.prototype.Halfedge.prototype.getStartpoint = function() {
-    return this.edge.lSite === this.site ? this.edge.va : this.edge.vb;
-    };
-
-Voronoi.prototype.Halfedge.prototype.getEndpoint = function() {
-    return this.edge.lSite === this.site ? this.edge.vb : this.edge.va;
-    };
-
-
-
-// this create and add a vertex to the internal collection
-
-Voronoi.prototype.createVertex = function(x, y) {
-    var v = this.vertexJunkyard.pop();
-    if ( !v ) {
-        v = new this.Vertex(x, y);
-        }
-    else {
-        v.x = x;
-        v.y = y;
-        }
-    this.vertices.push(v);
-    return v;
-    };
-
-// this create and add an edge to internal collection, and also create
-// two halfedges which are added to each site's counterclockwise array
-// of halfedges.
-
-Voronoi.prototype.createEdge = function(lSite, rSite, va, vb) {
-    var edge = this.edgeJunkyard.pop();
-    if ( !edge ) {
-        edge = new this.Edge(lSite, rSite);
-        }
-    else {
-        edge.lSite = lSite;
-        edge.rSite = rSite;
-        edge.va = edge.vb = null;
-        }
-
-    this.edges.push(edge);
-    if (va) {
-        this.setEdgeStartpoint(edge, lSite, rSite, va);
-        }
-    if (vb) {
-        this.setEdgeEndpoint(edge, lSite, rSite, vb);
-        }
-    this.cells[lSite.voronoiId].halfedges.push(this.createHalfedge(edge, lSite, rSite));
-    this.cells[rSite.voronoiId].halfedges.push(this.createHalfedge(edge, rSite, lSite));
-    return edge;
-    };
-
-Voronoi.prototype.createBorderEdge = function(lSite, va, vb) {
-    var edge = this.edgeJunkyard.pop();
-    if ( !edge ) {
-        edge = new this.Edge(lSite, null);
-        }
-    else {
-        edge.lSite = lSite;
-        edge.rSite = null;
-        }
-    edge.va = va;
-    edge.vb = vb;
-    this.edges.push(edge);
-    return edge;
-    };
-
-Voronoi.prototype.setEdgeStartpoint = function(edge, lSite, rSite, vertex) {
-    if (!edge.va && !edge.vb) {
-        edge.va = vertex;
-        edge.lSite = lSite;
-        edge.rSite = rSite;
-        }
-    else if (edge.lSite === rSite) {
-        edge.vb = vertex;
-        }
-    else {
-        edge.va = vertex;
-        }
-    };
-
-Voronoi.prototype.setEdgeEndpoint = function(edge, lSite, rSite, vertex) {
-    this.setEdgeStartpoint(edge, rSite, lSite, vertex);
-    };
-
-// ---------------------------------------------------------------------------
-// Beachline methods
-
-// rhill 2011-06-07: For some reasons, performance suffers significantly
-// when instanciating a literal object instead of an empty ctor
-Voronoi.prototype.Beachsection = function() {
-    };
-
-// rhill 2011-06-02: A lot of Beachsection instanciations
-// occur during the computation of the Voronoi diagram,
-// somewhere between the number of sites and twice the
-// number of sites, while the number of Beachsections on the
-// beachline at any given time is comparatively low. For this
-// reason, we reuse already created Beachsections, in order
-// to avoid new memory allocation. This resulted in a measurable
-// performance gain.
-
-Voronoi.prototype.createBeachsection = function(site) {
-    var beachsection = this.beachsectionJunkyard.pop();
-    if (!beachsection) {
-        beachsection = new this.Beachsection();
-        }
-    beachsection.site = site;
-    return beachsection;
-    };
-
-// calculate the left break point of a particular beach section,
-// given a particular sweep line
-Voronoi.prototype.leftBreakPoint = function(arc, directrix) {
-    // http://en.wikipedia.org/wiki/Parabola
-    // http://en.wikipedia.org/wiki/Quadratic_equation
-    // h1 = x1,
-    // k1 = (y1+directrix)/2,
-    // h2 = x2,
-    // k2 = (y2+directrix)/2,
-    // p1 = k1-directrix,
-    // a1 = 1/(4*p1),
-    // b1 = -h1/(2*p1),
-    // c1 = h1*h1/(4*p1)+k1,
-    // p2 = k2-directrix,
-    // a2 = 1/(4*p2),
-    // b2 = -h2/(2*p2),
-    // c2 = h2*h2/(4*p2)+k2,
-    // x = (-(b2-b1) + Math.sqrt((b2-b1)*(b2-b1) - 4*(a2-a1)*(c2-c1))) / (2*(a2-a1))
-    // When x1 become the x-origin:
-    // h1 = 0,
-    // k1 = (y1+directrix)/2,
-    // h2 = x2-x1,
-    // k2 = (y2+directrix)/2,
-    // p1 = k1-directrix,
-    // a1 = 1/(4*p1),
-    // b1 = 0,
-    // c1 = k1,
-    // p2 = k2-directrix,
-    // a2 = 1/(4*p2),
-    // b2 = -h2/(2*p2),
-    // c2 = h2*h2/(4*p2)+k2,
-    // x = (-b2 + Math.sqrt(b2*b2 - 4*(a2-a1)*(c2-k1))) / (2*(a2-a1)) + x1
-
-    // change code below at your own risk: care has been taken to
-    // reduce errors due to computers' finite arithmetic precision.
-    // Maybe can still be improved, will see if any more of this
-    // kind of errors pop up again.
-    var site = arc.site,
-        rfocx = site.x,
-        rfocy = site.y,
-        pby2 = rfocy-directrix;
-    // parabola in degenerate case where focus is on directrix
-    if (!pby2) {
-        return rfocx;
-        }
-    var lArc = arc.rbPrevious;
-    if (!lArc) {
-        return -Infinity;
-        }
-    site = lArc.site;
-    var lfocx = site.x,
-        lfocy = site.y,
-        plby2 = lfocy-directrix;
-    // parabola in degenerate case where focus is on directrix
-    if (!plby2) {
-        return lfocx;
-        }
-    var hl = lfocx-rfocx,
-        aby2 = 1/pby2-1/plby2,
-        b = hl/plby2;
-    if (aby2) {
-        return (-b+this.sqrt(b*b-2*aby2*(hl*hl/(-2*plby2)-lfocy+plby2/2+rfocy-pby2/2)))/aby2+rfocx;
-        }
-    // both parabolas have same distance to directrix, thus break point is midway
-    return (rfocx+lfocx)/2;
-    };
-
-// calculate the right break point of a particular beach section,
-// given a particular directrix
-Voronoi.prototype.rightBreakPoint = function(arc, directrix) {
-    var rArc = arc.rbNext;
-    if (rArc) {
-        return this.leftBreakPoint(rArc, directrix);
-        }
-    var site = arc.site;
-    return site.y === directrix ? site.x : Infinity;
-    };
-
-Voronoi.prototype.detachBeachsection = function(beachsection) {
-    this.detachCircleEvent(beachsection); // detach potentially attached circle event
-    this.beachline.rbRemoveNode(beachsection); // remove from RB-tree
-    this.beachsectionJunkyard.push(beachsection); // mark for reuse
-    };
-
-Voronoi.prototype.removeBeachsection = function(beachsection) {
-    var circle = beachsection.circleEvent,
-        x = circle.x,
-        y = circle.ycenter,
-        vertex = this.createVertex(x, y),
-        previous = beachsection.rbPrevious,
-        next = beachsection.rbNext,
-        disappearingTransitions = [beachsection],
-        abs_fn = Math.abs;
-
-    // remove collapsed beachsection from beachline
-    this.detachBeachsection(beachsection);
-
-    // there could be more than one empty arc at the deletion point, this
-    // happens when more than two edges are linked by the same vertex,
-    // so we will collect all those edges by looking up both sides of
-    // the deletion point.
-    // by the way, there is *always* a predecessor/successor to any collapsed
-    // beach section, it's just impossible to have a collapsing first/last
-    // beach sections on the beachline, since they obviously are unconstrained
-    // on their left/right side.
-
-    // look left
-    var lArc = previous;
-    while (lArc.circleEvent && abs_fn(x-lArc.circleEvent.x)<1e-9 && abs_fn(y-lArc.circleEvent.ycenter)<1e-9) {
-        previous = lArc.rbPrevious;
-        disappearingTransitions.unshift(lArc);
-        this.detachBeachsection(lArc); // mark for reuse
-        lArc = previous;
-        }
-    // even though it is not disappearing, I will also add the beach section
-    // immediately to the left of the left-most collapsed beach section, for
-    // convenience, since we need to refer to it later as this beach section
-    // is the 'left' site of an edge for which a start point is set.
-    disappearingTransitions.unshift(lArc);
-    this.detachCircleEvent(lArc);
-
-    // look right
-    var rArc = next;
-    while (rArc.circleEvent && abs_fn(x-rArc.circleEvent.x)<1e-9 && abs_fn(y-rArc.circleEvent.ycenter)<1e-9) {
-        next = rArc.rbNext;
-        disappearingTransitions.push(rArc);
-        this.detachBeachsection(rArc); // mark for reuse
-        rArc = next;
-        }
-    // we also have to add the beach section immediately to the right of the
-    // right-most collapsed beach section, since there is also a disappearing
-    // transition representing an edge's start point on its left.
-    disappearingTransitions.push(rArc);
-    this.detachCircleEvent(rArc);
-
-    // walk through all the disappearing transitions between beach sections and
-    // set the start point of their (implied) edge.
-    var nArcs = disappearingTransitions.length,
-        iArc;
-    for (iArc=1; iArc<nArcs; iArc++) {
-        rArc = disappearingTransitions[iArc];
-        lArc = disappearingTransitions[iArc-1];
-        this.setEdgeStartpoint(rArc.edge, lArc.site, rArc.site, vertex);
-        }
-
-    // create a new edge as we have now a new transition between
-    // two beach sections which were previously not adjacent.
-    // since this edge appears as a new vertex is defined, the vertex
-    // actually define an end point of the edge (relative to the site
-    // on the left)
-    lArc = disappearingTransitions[0];
-    rArc = disappearingTransitions[nArcs-1];
-    rArc.edge = this.createEdge(lArc.site, rArc.site, undefined, vertex);
-
-    // create circle events if any for beach sections left in the beachline
-    // adjacent to collapsed sections
-    this.attachCircleEvent(lArc);
-    this.attachCircleEvent(rArc);
-    };
-
-Voronoi.prototype.addBeachsection = function(site) {
-    var x = site.x,
-        directrix = site.y;
-
-    // find the left and right beach sections which will surround the newly
-    // created beach section.
-    // rhill 2011-06-01: This loop is one of the most often executed,
-    // hence we expand in-place the comparison-against-epsilon calls.
-    var lArc, rArc,
-        dxl, dxr,
-        node = this.beachline.root;
-
-    while (node) {
-        dxl = this.leftBreakPoint(node,directrix)-x;
-        // x lessThanWithEpsilon xl => falls somewhere before the left edge of the beachsection
-        if (dxl > 1e-9) {
-            // this case should never happen
-            // if (!node.rbLeft) {
-            //    rArc = node.rbLeft;
-            //    break;
-            //    }
-            node = node.rbLeft;
-            }
-        else {
-            dxr = x-this.rightBreakPoint(node,directrix);
-            // x greaterThanWithEpsilon xr => falls somewhere after the right edge of the beachsection
-            if (dxr > 1e-9) {
-                if (!node.rbRight) {
-                    lArc = node;
-                    break;
-                    }
-                node = node.rbRight;
-                }
-            else {
-                // x equalWithEpsilon xl => falls exactly on the left edge of the beachsection
-                if (dxl > -1e-9) {
-                    lArc = node.rbPrevious;
-                    rArc = node;
-                    }
-                // x equalWithEpsilon xr => falls exactly on the right edge of the beachsection
-                else if (dxr > -1e-9) {
-                    lArc = node;
-                    rArc = node.rbNext;
-                    }
-                // falls exactly somewhere in the middle of the beachsection
-                else {
-                    lArc = rArc = node;
-                    }
-                break;
-                }
-            }
-        }
-    // at this point, keep in mind that lArc and/or rArc could be
-    // undefined or null.
-
-    // create a new beach section object for the site and add it to RB-tree
-    var newArc = this.createBeachsection(site);
-    this.beachline.rbInsertSuccessor(lArc, newArc);
-
-    // cases:
-    //
-
-    // [null,null]
-    // least likely case: new beach section is the first beach section on the
-    // beachline.
-    // This case means:
-    //   no new transition appears
-    //   no collapsing beach section
-    //   new beachsection become root of the RB-tree
-    if (!lArc && !rArc) {
-        return;
-        }
-
-    // [lArc,rArc] where lArc == rArc
-    // most likely case: new beach section split an existing beach
-    // section.
-    // This case means:
-    //   one new transition appears
-    //   the left and right beach section might be collapsing as a result
-    //   two new nodes added to the RB-tree
-    if (lArc === rArc) {
-        // invalidate circle event of split beach section
-        this.detachCircleEvent(lArc);
-
-        // split the beach section into two separate beach sections
-        rArc = this.createBeachsection(lArc.site);
-        this.beachline.rbInsertSuccessor(newArc, rArc);
-
-        // since we have a new transition between two beach sections,
-        // a new edge is born
-        newArc.edge = rArc.edge = this.createEdge(lArc.site, newArc.site);
-
-        // check whether the left and right beach sections are collapsing
-        // and if so create circle events, to be notified when the point of
-        // collapse is reached.
-        this.attachCircleEvent(lArc);
-        this.attachCircleEvent(rArc);
-        return;
-        }
-
-    // [lArc,null]
-    // even less likely case: new beach section is the *last* beach section
-    // on the beachline -- this can happen *only* if *all* the previous beach
-    // sections currently on the beachline share the same y value as
-    // the new beach section.
-    // This case means:
-    //   one new transition appears
-    //   no collapsing beach section as a result
-    //   new beach section become right-most node of the RB-tree
-    if (lArc && !rArc) {
-        newArc.edge = this.createEdge(lArc.site,newArc.site);
-        return;
-        }
-
-    // [null,rArc]
-    // impossible case: because sites are strictly processed from top to bottom,
-    // and left to right, which guarantees that there will always be a beach section
-    // on the left -- except of course when there are no beach section at all on
-    // the beach line, which case was handled above.
-    // rhill 2011-06-02: No point testing in non-debug version
-    //if (!lArc && rArc) {
-    //    throw "Voronoi.addBeachsection(): What is this I don't even";
-    //    }
-
-    // [lArc,rArc] where lArc != rArc
-    // somewhat less likely case: new beach section falls *exactly* in between two
-    // existing beach sections
-    // This case means:
-    //   one transition disappears
-    //   two new transitions appear
-    //   the left and right beach section might be collapsing as a result
-    //   only one new node added to the RB-tree
-    if (lArc !== rArc) {
-        // invalidate circle events of left and right sites
-        this.detachCircleEvent(lArc);
-        this.detachCircleEvent(rArc);
-
-        // an existing transition disappears, meaning a vertex is defined at
-        // the disappearance point.
-        // since the disappearance is caused by the new beachsection, the
-        // vertex is at the center of the circumscribed circle of the left,
-        // new and right beachsections.
-        // http://mathforum.org/library/drmath/view/55002.html
-        // Except that I bring the origin at A to simplify
-        // calculation
-        var lSite = lArc.site,
-            ax = lSite.x,
-            ay = lSite.y,
-            bx=site.x-ax,
-            by=site.y-ay,
-            rSite = rArc.site,
-            cx=rSite.x-ax,
-            cy=rSite.y-ay,
-            d=2*(bx*cy-by*cx),
-            hb=bx*bx+by*by,
-            hc=cx*cx+cy*cy,
-            vertex = this.createVertex((cy*hb-by*hc)/d+ax, (bx*hc-cx*hb)/d+ay);
-
-        // one transition disappear
-        this.setEdgeStartpoint(rArc.edge, lSite, rSite, vertex);
-
-        // two new transitions appear at the new vertex location
-        newArc.edge = this.createEdge(lSite, site, undefined, vertex);
-        rArc.edge = this.createEdge(site, rSite, undefined, vertex);
-
-        // check whether the left and right beach sections are collapsing
-        // and if so create circle events, to handle the point of collapse.
-        this.attachCircleEvent(lArc);
-        this.attachCircleEvent(rArc);
-        return;
-        }
-    };
-
-// ---------------------------------------------------------------------------
-// Circle event methods
-
-// rhill 2011-06-07: For some reasons, performance suffers significantly
-// when instanciating a literal object instead of an empty ctor
-Voronoi.prototype.CircleEvent = function() {
-    // rhill 2013-10-12: it helps to state exactly what we are at ctor time.
-    this.arc = null;
-    this.rbLeft = null;
-    this.rbNext = null;
-    this.rbParent = null;
-    this.rbPrevious = null;
-    this.rbRed = false;
-    this.rbRight = null;
-    this.site = null;
-    this.x = this.y = this.ycenter = 0;
-    };
-
-Voronoi.prototype.attachCircleEvent = function(arc) {
-    var lArc = arc.rbPrevious,
-        rArc = arc.rbNext;
-    if (!lArc || !rArc) {return;} // does that ever happen?
-    var lSite = lArc.site,
-        cSite = arc.site,
-        rSite = rArc.site;
-
-    // If site of left beachsection is same as site of
-    // right beachsection, there can't be convergence
-    if (lSite===rSite) {return;}
-
-    // Find the circumscribed circle for the three sites associated
-    // with the beachsection triplet.
-    // rhill 2011-05-26: It is more efficient to calculate in-place
-    // rather than getting the resulting circumscribed circle from an
-    // object returned by calling Voronoi.circumcircle()
-    // http://mathforum.org/library/drmath/view/55002.html
-    // Except that I bring the origin at cSite to simplify calculations.
-    // The bottom-most part of the circumcircle is our Fortune 'circle
-    // event', and its center is a vertex potentially part of the final
-    // Voronoi diagram.
-    var bx = cSite.x,
-        by = cSite.y,
-        ax = lSite.x-bx,
-        ay = lSite.y-by,
-        cx = rSite.x-bx,
-        cy = rSite.y-by;
-
-    // If points l->c->r are clockwise, then center beach section does not
-    // collapse, hence it can't end up as a vertex (we reuse 'd' here, which
-    // sign is reverse of the orientation, hence we reverse the test.
-    // http://en.wikipedia.org/wiki/Curve_orientation#Orientation_of_a_simple_polygon
-    // rhill 2011-05-21: Nasty finite precision error which caused circumcircle() to
-    // return infinites: 1e-12 seems to fix the problem.
-    var d = 2*(ax*cy-ay*cx);
-    if (d >= -2e-12){return;}
-
-    var ha = ax*ax+ay*ay,
-        hc = cx*cx+cy*cy,
-        x = (cy*ha-ay*hc)/d,
-        y = (ax*hc-cx*ha)/d,
-        ycenter = y+by;
-
-    // Important: ybottom should always be under or at sweep, so no need
-    // to waste CPU cycles by checking
-
-    // recycle circle event object if possible
-    var circleEvent = this.circleEventJunkyard.pop();
-    if (!circleEvent) {
-        circleEvent = new this.CircleEvent();
-        }
-    circleEvent.arc = arc;
-    circleEvent.site = cSite;
-    circleEvent.x = x+bx;
-    circleEvent.y = ycenter+this.sqrt(x*x+y*y); // y bottom
-    circleEvent.ycenter = ycenter;
-    arc.circleEvent = circleEvent;
-
-    // find insertion point in RB-tree: circle events are ordered from
-    // smallest to largest
-    var predecessor = null,
-        node = this.circleEvents.root;
-    while (node) {
-        if (circleEvent.y < node.y || (circleEvent.y === node.y && circleEvent.x <= node.x)) {
-            if (node.rbLeft) {
-                node = node.rbLeft;
-                }
-            else {
-                predecessor = node.rbPrevious;
-                break;
-                }
-            }
-        else {
-            if (node.rbRight) {
-                node = node.rbRight;
-                }
-            else {
-                predecessor = node;
-                break;
-                }
-            }
-        }
-    this.circleEvents.rbInsertSuccessor(predecessor, circleEvent);
-    if (!predecessor) {
-        this.firstCircleEvent = circleEvent;
-        }
-    };
-
-Voronoi.prototype.detachCircleEvent = function(arc) {
-    var circleEvent = arc.circleEvent;
-    if (circleEvent) {
-        if (!circleEvent.rbPrevious) {
-            this.firstCircleEvent = circleEvent.rbNext;
-            }
-        this.circleEvents.rbRemoveNode(circleEvent); // remove from RB-tree
-        this.circleEventJunkyard.push(circleEvent);
-        arc.circleEvent = null;
-        }
-    };
-
-// ---------------------------------------------------------------------------
-// Diagram completion methods
-
-// connect dangling edges (not if a cursory test tells us
-// it is not going to be visible.
-// return value:
-//   false: the dangling endpoint couldn't be connected
-//   true: the dangling endpoint could be connected
-Voronoi.prototype.connectEdge = function(edge, bbox) {
-    // skip if end point already connected
-    var vb = edge.vb;
-    if (!!vb) {return true;}
-
-    // make local copy for performance purpose
-    var va = edge.va,
-        xl = bbox.xl,
-        xr = bbox.xr,
-        yt = bbox.yt,
-        yb = bbox.yb,
-        lSite = edge.lSite,
-        rSite = edge.rSite,
-        lx = lSite.x,
-        ly = lSite.y,
-        rx = rSite.x,
-        ry = rSite.y,
-        fx = (lx+rx)/2,
-        fy = (ly+ry)/2,
-        fm, fb;
-
-    // if we reach here, this means cells which use this edge will need
-    // to be closed, whether because the edge was removed, or because it
-    // was connected to the bounding box.
-    this.cells[lSite.voronoiId].closeMe = true;
-    this.cells[rSite.voronoiId].closeMe = true;
-
-    // get the line equation of the bisector if line is not vertical
-    if (ry !== ly) {
-        fm = (lx-rx)/(ry-ly);
-        fb = fy-fm*fx;
-        }
-
-    // remember, direction of line (relative to left site):
-    // upward: left.x < right.x
-    // downward: left.x > right.x
-    // horizontal: left.x == right.x
-    // upward: left.x < right.x
-    // rightward: left.y < right.y
-    // leftward: left.y > right.y
-    // vertical: left.y == right.y
-
-    // depending on the direction, find the best side of the
-    // bounding box to use to determine a reasonable start point
-
-    // rhill 2013-12-02:
-    // While at it, since we have the values which define the line,
-    // clip the end of va if it is outside the bbox.
-    // https://github.com/gorhill/Javascript-Voronoi/issues/15
-    // TODO: Do all the clipping here rather than rely on Liang-Barsky
-    // which does not do well sometimes due to loss of arithmetic
-    // precision. The code here doesn't degrade if one of the vertex is
-    // at a huge distance.
-
-    // special case: vertical line
-    if (fm === undefined) {
-        // doesn't intersect with viewport
-        if (fx < xl || fx >= xr) {return false;}
-        // downward
-        if (lx > rx) {
-            if (!va || va.y < yt) {
-                va = this.createVertex(fx, yt);
-                }
-            else if (va.y >= yb) {
-                return false;
-                }
-            vb = this.createVertex(fx, yb);
-            }
-        // upward
-        else {
-            if (!va || va.y > yb) {
-                va = this.createVertex(fx, yb);
-                }
-            else if (va.y < yt) {
-                return false;
-                }
-            vb = this.createVertex(fx, yt);
-            }
-        }
-    // closer to vertical than horizontal, connect start point to the
-    // top or bottom side of the bounding box
-    else if (fm < -1 || fm > 1) {
-        // downward
-        if (lx > rx) {
-            if (!va || va.y < yt) {
-                va = this.createVertex((yt-fb)/fm, yt);
-                }
-            else if (va.y >= yb) {
-                return false;
-                }
-            vb = this.createVertex((yb-fb)/fm, yb);
-            }
-        // upward
-        else {
-            if (!va || va.y > yb) {
-                va = this.createVertex((yb-fb)/fm, yb);
-                }
-            else if (va.y < yt) {
-                return false;
-                }
-            vb = this.createVertex((yt-fb)/fm, yt);
-            }
-        }
-    // closer to horizontal than vertical, connect start point to the
-    // left or right side of the bounding box
-    else {
-        // rightward
-        if (ly < ry) {
-            if (!va || va.x < xl) {
-                va = this.createVertex(xl, fm*xl+fb);
-                }
-            else if (va.x >= xr) {
-                return false;
-                }
-            vb = this.createVertex(xr, fm*xr+fb);
-            }
-        // leftward
-        else {
-            if (!va || va.x > xr) {
-                va = this.createVertex(xr, fm*xr+fb);
-                }
-            else if (va.x < xl) {
-                return false;
-                }
-            vb = this.createVertex(xl, fm*xl+fb);
-            }
-        }
-    edge.va = va;
-    edge.vb = vb;
-
-    return true;
-    };
-
-// line-clipping code taken from:
-//   Liang-Barsky function by Daniel White
-//   http://www.skytopia.com/project/articles/compsci/clipping.html
-// Thanks!
-// A bit modified to minimize code paths
-Voronoi.prototype.clipEdge = function(edge, bbox) {
-    var ax = edge.va.x,
-        ay = edge.va.y,
-        bx = edge.vb.x,
-        by = edge.vb.y,
-        t0 = 0,
-        t1 = 1,
-        dx = bx-ax,
-        dy = by-ay;
-    // left
-    var q = ax-bbox.xl;
-    if (dx===0 && q<0) {return false;}
-    var r = -q/dx;
-    if (dx<0) {
-        if (r<t0) {return false;}
-        if (r<t1) {t1=r;}
-        }
-    else if (dx>0) {
-        if (r>t1) {return false;}
-        if (r>t0) {t0=r;}
-        }
-    // right
-    q = bbox.xr-ax;
-    if (dx===0 && q<0) {return false;}
-    r = q/dx;
-    if (dx<0) {
-        if (r>t1) {return false;}
-        if (r>t0) {t0=r;}
-        }
-    else if (dx>0) {
-        if (r<t0) {return false;}
-        if (r<t1) {t1=r;}
-        }
-    // top
-    q = ay-bbox.yt;
-    if (dy===0 && q<0) {return false;}
-    r = -q/dy;
-    if (dy<0) {
-        if (r<t0) {return false;}
-        if (r<t1) {t1=r;}
-        }
-    else if (dy>0) {
-        if (r>t1) {return false;}
-        if (r>t0) {t0=r;}
-        }
-    // bottom        
-    q = bbox.yb-ay;
-    if (dy===0 && q<0) {return false;}
-    r = q/dy;
-    if (dy<0) {
-        if (r>t1) {return false;}
-        if (r>t0) {t0=r;}
-        }
-    else if (dy>0) {
-        if (r<t0) {return false;}
-        if (r<t1) {t1=r;}
-        }
-
-    // if we reach this point, Voronoi edge is within bbox
-
-    // if t0 > 0, va needs to change
-    // rhill 2011-06-03: we need to create a new vertex rather
-    // than modifying the existing one, since the existing
-    // one is likely shared with at least another edge
-    if (t0 > 0) {
-        edge.va = this.createVertex(ax+t0*dx, ay+t0*dy);
-        }
-
-    // if t1 < 1, vb needs to change
-    // rhill 2011-06-03: we need to create a new vertex rather
-    // than modifying the existing one, since the existing
-    // one is likely shared with at least another edge
-    if (t1 < 1) {
-        edge.vb = this.createVertex(ax+t1*dx, ay+t1*dy);
-        }
-
-    // va and/or vb were clipped, thus we will need to close
-    // cells which use this edge.
-    if ( t0 > 0 || t1 < 1 ) {
-        this.cells[edge.lSite.voronoiId].closeMe = true;
-        this.cells[edge.rSite.voronoiId].closeMe = true;
-    }
-
-    return true;
-    };
-
-// Connect/cut edges at bounding box
-Voronoi.prototype.clipEdges = function(bbox) {
-    // connect all dangling edges to bounding box
-    // or get rid of them if it can't be done
-    var edges = this.edges,
-        iEdge = edges.length,
-        edge,
-        abs_fn = Math.abs;
-
-    // iterate backward so we can splice safely
-    while (iEdge--) {
-        edge = edges[iEdge];
-        // edge is removed if:
-        //   it is wholly outside the bounding box
-        //   it is looking more like a point than a line
-        if (!this.connectEdge(edge, bbox) ||
-            !this.clipEdge(edge, bbox) ||
-            (abs_fn(edge.va.x-edge.vb.x)<1e-9 && abs_fn(edge.va.y-edge.vb.y)<1e-9)) {
-            edge.va = edge.vb = null;
-            edges.splice(iEdge,1);
-            }
-        }
-    };
-
-// Close the cells.
-// The cells are bound by the supplied bounding box.
-// Each cell refers to its associated site, and a list
-// of halfedges ordered counterclockwise.
-Voronoi.prototype.closeCells = function(bbox) {
-    var xl = bbox.xl,
-        xr = bbox.xr,
-        yt = bbox.yt,
-        yb = bbox.yb,
-        cells = this.cells,
-        iCell = cells.length,
-        cell,
-        iLeft,
-        halfedges, nHalfedges,
-        edge,
-        va, vb, vz,
-        lastBorderSegment,
-        abs_fn = Math.abs;
-
-    while (iCell--) {
-        cell = cells[iCell];
-        // prune, order halfedges counterclockwise, then add missing ones
-        // required to close cells
-        if (!cell.prepareHalfedges()) {
-            continue;
-            }
-        if (!cell.closeMe) {
-            continue;
-            }
-        // find first 'unclosed' point.
-        // an 'unclosed' point will be the end point of a halfedge which
-        // does not match the start point of the following halfedge
-        halfedges = cell.halfedges;
-        nHalfedges = halfedges.length;
-        // special case: only one site, in which case, the viewport is the cell
-        // ...
-
-        // all other cases
-        iLeft = 0;
-        while (iLeft < nHalfedges) {
-            va = halfedges[iLeft].getEndpoint();
-            vz = halfedges[(iLeft+1) % nHalfedges].getStartpoint();
-            // if end point is not equal to start point, we need to add the missing
-            // halfedge(s) up to vz
-            if (abs_fn(va.x-vz.x)>=1e-9 || abs_fn(va.y-vz.y)>=1e-9) {
-
-                // rhill 2013-12-02:
-                // "Holes" in the halfedges are not necessarily always adjacent.
-                // https://github.com/gorhill/Javascript-Voronoi/issues/16
-
-                // find entry point:
-                switch (true) {
-
-                    // walk downward along left side
-                    case this.equalWithEpsilon(va.x,xl) && this.lessThanWithEpsilon(va.y,yb):
-                        lastBorderSegment = this.equalWithEpsilon(vz.x,xl);
-                        vb = this.createVertex(xl, lastBorderSegment ? vz.y : yb);
-                        edge = this.createBorderEdge(cell.site, va, vb);
-                        iLeft++;
-                        halfedges.splice(iLeft, 0, this.createHalfedge(edge, cell.site, null));
-                        nHalfedges++;
-                        if ( lastBorderSegment ) { break; }
-                        va = vb;
-                        // fall through
-
-                    // walk rightward along bottom side
-                    case this.equalWithEpsilon(va.y,yb) && this.lessThanWithEpsilon(va.x,xr):
-                        lastBorderSegment = this.equalWithEpsilon(vz.y,yb);
-                        vb = this.createVertex(lastBorderSegment ? vz.x : xr, yb);
-                        edge = this.createBorderEdge(cell.site, va, vb);
-                        iLeft++;
-                        halfedges.splice(iLeft, 0, this.createHalfedge(edge, cell.site, null));
-                        nHalfedges++;
-                        if ( lastBorderSegment ) { break; }
-                        va = vb;
-                        // fall through
-
-                    // walk upward along right side
-                    case this.equalWithEpsilon(va.x,xr) && this.greaterThanWithEpsilon(va.y,yt):
-                        lastBorderSegment = this.equalWithEpsilon(vz.x,xr);
-                        vb = this.createVertex(xr, lastBorderSegment ? vz.y : yt);
-                        edge = this.createBorderEdge(cell.site, va, vb);
-                        iLeft++;
-                        halfedges.splice(iLeft, 0, this.createHalfedge(edge, cell.site, null));
-                        nHalfedges++;
-                        if ( lastBorderSegment ) { break; }
-                        va = vb;
-                        // fall through
-
-                    // walk leftward along top side
-                    case this.equalWithEpsilon(va.y,yt) && this.greaterThanWithEpsilon(va.x,xl):
-                        lastBorderSegment = this.equalWithEpsilon(vz.y,yt);
-                        vb = this.createVertex(lastBorderSegment ? vz.x : xl, yt);
-                        edge = this.createBorderEdge(cell.site, va, vb);
-                        iLeft++;
-                        halfedges.splice(iLeft, 0, this.createHalfedge(edge, cell.site, null));
-                        nHalfedges++;
-                        if ( lastBorderSegment ) { break; }
-                        va = vb;
-                        // fall through
-
-                        // walk downward along left side
-                        lastBorderSegment = this.equalWithEpsilon(vz.x,xl);
-                        vb = this.createVertex(xl, lastBorderSegment ? vz.y : yb);
-                        edge = this.createBorderEdge(cell.site, va, vb);
-                        iLeft++;
-                        halfedges.splice(iLeft, 0, this.createHalfedge(edge, cell.site, null));
-                        nHalfedges++;
-                        if ( lastBorderSegment ) { break; }
-                        va = vb;
-                        // fall through
-
-                        // walk rightward along bottom side
-                        lastBorderSegment = this.equalWithEpsilon(vz.y,yb);
-                        vb = this.createVertex(lastBorderSegment ? vz.x : xr, yb);
-                        edge = this.createBorderEdge(cell.site, va, vb);
-                        iLeft++;
-                        halfedges.splice(iLeft, 0, this.createHalfedge(edge, cell.site, null));
-                        nHalfedges++;
-                        if ( lastBorderSegment ) { break; }
-                        va = vb;
-                        // fall through
-
-                        // walk upward along right side
-                        lastBorderSegment = this.equalWithEpsilon(vz.x,xr);
-                        vb = this.createVertex(xr, lastBorderSegment ? vz.y : yt);
-                        edge = this.createBorderEdge(cell.site, va, vb);
-                        iLeft++;
-                        halfedges.splice(iLeft, 0, this.createHalfedge(edge, cell.site, null));
-                        nHalfedges++;
-                        if ( lastBorderSegment ) { break; }
-                        // fall through
-
-                    default:
-                        throw "Voronoi.closeCells() > this makes no sense!";
-                    }
-                }
-            iLeft++;
-            }
-        cell.closeMe = false;
-        }
-    };
-
-// ---------------------------------------------------------------------------
-// Debugging helper
-/*
-Voronoi.prototype.dumpBeachline = function(y) {
-    console.log('Voronoi.dumpBeachline(%f) > Beachsections, from left to right:', y);
-    if ( !this.beachline ) {
-        console.log('  None');
-        }
-    else {
-        var bs = this.beachline.getFirst(this.beachline.root);
-        while ( bs ) {
-            console.log('  site %d: xl: %f, xr: %f', bs.site.voronoiId, this.leftBreakPoint(bs, y), this.rightBreakPoint(bs, y));
-            bs = bs.rbNext;
-            }
-        }
-    };
-*/
-
-// ---------------------------------------------------------------------------
-// Helper: Quantize sites
-
-// rhill 2013-10-12:
-// This is to solve https://github.com/gorhill/Javascript-Voronoi/issues/15
-// Since not all users will end up using the kind of coord values which would
-// cause the issue to arise, I chose to let the user decide whether or not
-// he should sanitize his coord values through this helper. This way, for
-// those users who uses coord values which are known to be fine, no overhead is
-// added.
-
-Voronoi.prototype.quantizeSites = function(sites) {
-    var ε = this.ε,
-        n = sites.length,
-        site;
-    while ( n-- ) {
-        site = sites[n];
-        site.x = Math.floor(site.x / ε) * ε;
-        site.y = Math.floor(site.y / ε) * ε;
-        }
-    };
-
-// ---------------------------------------------------------------------------
-// Helper: Recycle diagram: all vertex, edge and cell objects are
-// "surrendered" to the Voronoi object for reuse.
-// TODO: rhill-voronoi-core v2: more performance to be gained
-// when I change the semantic of what is returned.
-
-Voronoi.prototype.recycle = function(diagram) {
-    if ( diagram ) {
-        if ( diagram instanceof this.Diagram ) {
-            this.toRecycle = diagram;
-            }
-        else {
-            throw 'Voronoi.recycleDiagram() > Need a Diagram object.';
-            }
-        }
-    };
-
-// ---------------------------------------------------------------------------
-// Top-level Fortune loop
-
-// rhill 2011-05-19:
-//   Voronoi sites are kept client-side now, to allow
-//   user to freely modify content. At compute time,
-//   *references* to sites are copied locally.
-
-Voronoi.prototype.compute = function(sites, bbox) {
-    // to measure execution time
-    var startTime = new Date();
-
-    // init internal state
-    this.reset();
-
-    // any diagram data available for recycling?
-    // I do that here so that this is included in execution time
-    if ( this.toRecycle ) {
-        this.vertexJunkyard = this.vertexJunkyard.concat(this.toRecycle.vertices);
-        this.edgeJunkyard = this.edgeJunkyard.concat(this.toRecycle.edges);
-        this.cellJunkyard = this.cellJunkyard.concat(this.toRecycle.cells);
-        this.toRecycle = null;
-        }
-
-    // Initialize site event queue
-    var siteEvents = sites.slice(0);
-    siteEvents.sort(function(a,b){
-        var r = b.y - a.y;
-        if (r) {return r;}
-        return b.x - a.x;
-        });
-
-    // process queue
-    var site = siteEvents.pop(),
-        siteid = 0,
-        xsitex, // to avoid duplicate sites
-        xsitey,
-        cells = this.cells,
-        circle;
-
-    // main loop
-    for (;;) {
-        // we need to figure whether we handle a site or circle event
-        // for this we find out if there is a site event and it is
-        // 'earlier' than the circle event
-        circle = this.firstCircleEvent;
-
-        // add beach section
-        if (site && (!circle || site.y < circle.y || (site.y === circle.y && site.x < circle.x))) {
-            // only if site is not a duplicate
-            if (site.x !== xsitex || site.y !== xsitey) {
-                // first create cell for new site
-                cells[siteid] = this.createCell(site);
-                site.voronoiId = siteid++;
-                // then create a beachsection for that site
-                this.addBeachsection(site);
-                // remember last site coords to detect duplicate
-                xsitey = site.y;
-                xsitex = site.x;
-                }
-            site = siteEvents.pop();
-            }
-
-        // remove beach section
-        else if (circle) {
-            this.removeBeachsection(circle.arc);
-            }
-
-        // all done, quit
-        else {
-            break;
-            }
-        }
-
-    // wrapping-up:
-    //   connect dangling edges to bounding box
-    //   cut edges as per bounding box
-    //   discard edges completely outside bounding box
-    //   discard edges which are point-like
-    this.clipEdges(bbox);
-
-    //   add missing edges in order to close opened cells
-    this.closeCells(bbox);
-
-    // to measure execution time
-    var stopTime = new Date();
-
-    // prepare return values
-    var diagram = new this.Diagram();
-    diagram.cells = this.cells;
-    diagram.edges = this.edges;
-    diagram.vertices = this.vertices;
-    diagram.execTime = stopTime.getTime()-startTime.getTime();
-
-    // clean up
-    this.reset();
-
-    return diagram;
-    };
-
-/******************************************************************************/
-
-// stuff below here was modified by sanine
-export default Voronoi;