Add d3.layout.voronoi.{links,triangles}.

d3.js

@@ -3794,7 +3794,7 @@ d3 = function() {
     var polygons = vertices.map(function() {
       return [];
     }), Z = 1e6;
-    d3_voronoi_tessellate(vertices, function(e) {
+    d3_geom_voronoiTessellate(vertices, function(e) {
       var s1, s2, x1, x2, y1, y2;
       if (e.a === 1 && e.b >= 0) {
         s1 = e.ep.r;
@@ -3853,11 +3853,11 @@ d3 = function() {
     });
     return polygons;
   };
-  var d3_voronoi_opposite = {
+  var d3_geom_voronoiOpposite = {
     l: "r",
     r: "l"
   };
-  function d3_voronoi_tessellate(vertices, callback) {
+  function d3_geom_voronoiTessellate(vertices, callback) {
     var Sites = {
       list: vertices.map(function(v, i) {
         return {
@@ -3919,7 +3919,7 @@ d3 = function() {
         return he.edge == null ? Sites.bottomSite : he.edge.region[he.side];
       },
       rightRegion: function(he) {
-        return he.edge == null ? Sites.bottomSite : he.edge.region[d3_voronoi_opposite[he.side]];
+        return he.edge == null ? Sites.bottomSite : he.edge.region[d3_geom_voronoiOpposite[he.side]];
       }
     };
     var Geom = {
@@ -4009,7 +4009,7 @@ d3 = function() {
       },
       endPoint: function(edge, side, site) {
         edge.ep[side] = site;
-        if (!edge.ep[d3_voronoi_opposite[side]]) return;
+        if (!edge.ep[d3_geom_voronoiOpposite[side]]) return;
         callback(edge);
       },
       distance: function(s, t) {
@@ -4109,7 +4109,7 @@ d3 = function() {
         e = Geom.bisect(bot, top);
         bisector = EdgeList.createHalfEdge(e, pm);
         EdgeList.insert(llbnd, bisector);
-        Geom.endPoint(e, d3_voronoi_opposite[pm], v);
+        Geom.endPoint(e, d3_geom_voronoiOpposite[pm], v);
         p = Geom.intersect(llbnd, bisector);
         if (p) {
           EventQueue.del(llbnd);
@@ -4131,7 +4131,7 @@ d3 = function() {
     var edges = vertices.map(function() {
       return [];
     }), triangles = [];
-    d3_voronoi_tessellate(vertices, function(e) {
+    d3_geom_voronoiTessellate(vertices, function(e) {
       edges[e.region.l.index].push(vertices[e.region.r.index]);
     });
     edges.forEach(function(edge, i) {
@@ -6204,6 +6204,30 @@ d3 = function() {
       }
       return voronoi;
     };
+    voronoi.links = function(data) {
+      var points = [], graph = [], links = [], fx = d3_functor(x), fy = d3_functor(y), d, i, n = data.length;
+      for (i = 0; i < n; ++i) points.push([ +fx.call(this, d = data[i], i), +fy.call(this, d, i) ]), 
+      graph.push([]);
+      d3_geom_voronoiTessellate(points, function(e) {
+        var l = e.region.l.index, r = e.region.r.index;
+        if (graph[l][r]) return;
+        graph[l][r] = graph[r][l] = true;
+        links.push({
+          source: points[l],
+          target: points[r]
+        });
+      });
+      return links;
+    };
+    voronoi.triangles = function(data) {
+      var points = [], point, fx = d3_functor(x), fy = d3_functor(y), d, i, n = data.length;
+      for (i = 0; i < n; ++i) {
+        point = [ +fx.call(this, d = data[i], i), +fy.call(this, d, i) ];
+        point.data = d;
+        points.push(point);
+      }
+      return d3.geom.delaunay(points);
+    };
     return voronoi;
   };
   d3.random = {

src/geom/delaunay.js

@@ -10,7 +10,7 @@ d3.geom.delaunay = function(vertices) {
       triangles = [];
 
   // Use the Voronoi tessellation to determine Delaunay edges.
-  d3_voronoi_tessellate(vertices, function(e) {
+  d3_geom_voronoiTessellate(vertices, function(e) {
     edges[e.region.l.index].push(vertices[e.region.r.index]);
   });
 

src/geom/voronoi.js

@@ -26,7 +26,7 @@ d3.geom.voronoi = function(vertices) {
   var polygons = vertices.map(function() { return []; }),
       Z = 1e6;
 
-  d3_voronoi_tessellate(vertices, function(e) {
+  d3_geom_voronoiTessellate(vertices, function(e) {
     var s1,
         s2,
         x1,
@@ -103,9 +103,9 @@ d3.geom.voronoi = function(vertices) {
   return polygons;
 };
 
-var d3_voronoi_opposite = {l: "r", r: "l"};
+var d3_geom_voronoiOpposite = {l: "r", r: "l"};
 
-function d3_voronoi_tessellate(vertices, callback) {
+function d3_geom_voronoiTessellate(vertices, callback) {
 
   var Sites = {
     list: vertices
@@ -188,7 +188,7 @@ function d3_voronoi_tessellate(vertices, callback) {
     rightRegion: function(he) {
       return he.edge == null
           ? Sites.bottomSite
-          : he.edge.region[d3_voronoi_opposite[he.side]];
+          : he.edge.region[d3_geom_voronoiOpposite[he.side]];
     }
   };
 
@@ -307,7 +307,7 @@ function d3_voronoi_tessellate(vertices, callback) {
 
     endPoint: function(edge, side, site) {
       edge.ep[side] = site;
-      if (!edge.ep[d3_voronoi_opposite[side]]) return;
+      if (!edge.ep[d3_geom_voronoiOpposite[side]]) return;
       callback(edge);
     },
 
@@ -422,7 +422,7 @@ function d3_voronoi_tessellate(vertices, callback) {
       e = Geom.bisect(bot, top);
       bisector = EdgeList.createHalfEdge(e, pm);
       EdgeList.insert(llbnd, bisector);
-      Geom.endPoint(e, d3_voronoi_opposite[pm], v);
+      Geom.endPoint(e, d3_geom_voronoiOpposite[pm], v);
       p = Geom.intersect(llbnd, bisector);
       if (p) {
         EventQueue.del(llbnd);

src/layout/voronoi.js

@@ -1,4 +1,5 @@
 import "../core/functor";
+import "../geom/delaunay";
 import "../geom/polygon";
 import "../geom/voronoi";
 import "../svg/line";
@@ -44,5 +45,41 @@ d3.layout.voronoi = function() {
     return voronoi;
   };
 
+  voronoi.links = function(data) {
+    var points = [],
+        graph = [],
+        links = [],
+        fx = d3_functor(x),
+        fy = d3_functor(y),
+        d,
+        i,
+        n = data.length;
+    for (i = 0; i < n; ++i) points.push([+fx.call(this, d = data[i], i), +fy.call(this, d, i)]), graph.push([]);
+    d3_geom_voronoiTessellate(points, function(e) {
+      var l = e.region.l.index,
+          r = e.region.r.index;
+      if (graph[l][r]) return;
+      graph[l][r] = graph[r][l] = true;
+      links.push({source: points[l], target: points[r]});
+    });
+    return links;
+  };
+
+  voronoi.triangles = function(data) {
+    var points = [],
+        point,
+        fx = d3_functor(x),
+        fy = d3_functor(y),
+        d,
+        i,
+        n = data.length;
+    for (i = 0; i < n; ++i) {
+      point = [+fx.call(this, d = data[i], i), +fy.call(this, d, i)];
+      point.data = d;
+      points.push(point);
+    }
+    return d3.geom.delaunay(points);
+  };
+
   return voronoi;
 };

test/layout/voronoi-test.js

@@ -60,6 +60,25 @@ suite.addBatch({
         "the returned cells' data points back to the input data": function(cells) {
           assert.deepEqual(cells.map(function(cell) { return cell.data; }), [[200, 200], [760, 300]]);
         }
+      },
+      "links": {
+        "for two points": function(v) {
+          assert.deepEqual(v.links([[200, 200], [760, 300]]), [
+            {source: [200, 200], target: [760, 300]}]);
+        },
+        "for three points": function(v) {
+          assert.deepEqual(v.links([[200, 200], [500, 250], [760, 300]]), [
+            {source: [200, 200], target: [760, 300]},
+            {source: [500, 250], target: [760, 300]},
+            {source: [200, 200], target: [500, 250]}]);
+        }
+      },
+      "triangles": {
+        "for three points": function(v) {
+          assert.deepEqual(v.triangles([[200, 200], [500, 250], [760, 300]]).map(function(d) {
+            return d.map(function(d) { return d.data; });
+          }), [[ [200, 200], [760, 300], [500, 250]]]);
+        }
       }
     },