diff -r efd9c589177a -r c0b4a8b5a012 toolkit/javascript/d3/src/layout/tree.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/toolkit/javascript/d3/src/layout/tree.js	Thu Apr 10 14:20:23 2014 +0200
@@ -0,0 +1,237 @@
+// Node-link tree diagram using the Reingold-Tilford "tidy" algorithm
+d3.layout.tree = function() {
+  var hierarchy = d3.layout.hierarchy().sort(null).value(null),
+      separation = d3_layout_treeSeparation,
+      size = [1, 1]; // width, height
+
+  function tree(d, i) {
+    var nodes = hierarchy.call(this, d, i),
+        root = nodes[0];
+
+    function firstWalk(node, previousSibling) {
+      var children = node.children,
+          layout = node._tree;
+      if (children && (n = children.length)) {
+        var n,
+            firstChild = children[0],
+            previousChild,
+            ancestor = firstChild,
+            child,
+            i = -1;
+        while (++i < n) {
+          child = children[i];
+          firstWalk(child, previousChild);
+          ancestor = apportion(child, previousChild, ancestor);
+          previousChild = child;
+        }
+        d3_layout_treeShift(node);
+        var midpoint = .5 * (firstChild._tree.prelim + child._tree.prelim);
+        if (previousSibling) {
+          layout.prelim = previousSibling._tree.prelim + separation(node, previousSibling);
+          layout.mod = layout.prelim - midpoint;
+        } else {
+          layout.prelim = midpoint;
+        }
+      } else {
+        if (previousSibling) {
+          layout.prelim = previousSibling._tree.prelim + separation(node, previousSibling);
+        }
+      }
+    }
+
+    function secondWalk(node, x) {
+      node.x = node._tree.prelim + x;
+      var children = node.children;
+      if (children && (n = children.length)) {
+        var i = -1,
+            n;
+        x += node._tree.mod;
+        while (++i < n) {
+          secondWalk(children[i], x);
+        }
+      }
+    }
+
+    function apportion(node, previousSibling, ancestor) {
+      if (previousSibling) {
+        var vip = node,
+            vop = node,
+            vim = previousSibling,
+            vom = node.parent.children[0],
+            sip = vip._tree.mod,
+            sop = vop._tree.mod,
+            sim = vim._tree.mod,
+            som = vom._tree.mod,
+            shift;
+        while (vim = d3_layout_treeRight(vim), vip = d3_layout_treeLeft(vip), vim && vip) {
+          vom = d3_layout_treeLeft(vom);
+          vop = d3_layout_treeRight(vop);
+          vop._tree.ancestor = node;
+          shift = vim._tree.prelim + sim - vip._tree.prelim - sip + separation(vim, vip);
+          if (shift > 0) {
+            d3_layout_treeMove(d3_layout_treeAncestor(vim, node, ancestor), node, shift);
+            sip += shift;
+            sop += shift;
+          }
+          sim += vim._tree.mod;
+          sip += vip._tree.mod;
+          som += vom._tree.mod;
+          sop += vop._tree.mod;
+        }
+        if (vim && !d3_layout_treeRight(vop)) {
+          vop._tree.thread = vim;
+          vop._tree.mod += sim - sop;
+        }
+        if (vip && !d3_layout_treeLeft(vom)) {
+          vom._tree.thread = vip;
+          vom._tree.mod += sip - som;
+          ancestor = node;
+        }
+      }
+      return ancestor;
+    }
+
+    // Initialize temporary layout variables.
+    d3_layout_treeVisitAfter(root, function(node, previousSibling) {
+      node._tree = {
+        ancestor: node,
+        prelim: 0,
+        mod: 0,
+        change: 0,
+        shift: 0,
+        number: previousSibling ? previousSibling._tree.number + 1 : 0
+      };
+    });
+
+    // Compute the layout using Buchheim et al.'s algorithm.
+    firstWalk(root);
+    secondWalk(root, -root._tree.prelim);
+
+    // Compute the left-most, right-most, and depth-most nodes for extents.
+    var left = d3_layout_treeSearch(root, d3_layout_treeLeftmost),
+        right = d3_layout_treeSearch(root, d3_layout_treeRightmost),
+        deep = d3_layout_treeSearch(root, d3_layout_treeDeepest),
+        x0 = left.x - separation(left, right) / 2,
+        x1 = right.x + separation(right, left) / 2,
+        y1 = deep.depth || 1;
+
+    // Clear temporary layout variables; transform x and y.
+    d3_layout_treeVisitAfter(root, function(node) {
+      node.x = (node.x - x0) / (x1 - x0) * size[0];
+      node.y = node.depth / y1 * size[1];
+      delete node._tree;
+    });
+
+    return nodes;
+  }
+
+  tree.separation = function(x) {
+    if (!arguments.length) return separation;
+    separation = x;
+    return tree;
+  };
+
+  tree.size = function(x) {
+    if (!arguments.length) return size;
+    size = x;
+    return tree;
+  };
+
+  return d3_layout_hierarchyRebind(tree, hierarchy);
+};
+
+function d3_layout_treeSeparation(a, b) {
+  return a.parent == b.parent ? 1 : 2;
+}
+
+// function d3_layout_treeSeparationRadial(a, b) {
+//   return (a.parent == b.parent ? 1 : 2) / a.depth;
+// }
+
+function d3_layout_treeLeft(node) {
+  var children = node.children;
+  return children && children.length ? children[0] : node._tree.thread;
+}
+
+function d3_layout_treeRight(node) {
+  var children = node.children,
+      n;
+  return children && (n = children.length) ? children[n - 1] : node._tree.thread;
+}
+
+function d3_layout_treeSearch(node, compare) {
+  var children = node.children;
+  if (children && (n = children.length)) {
+    var child,
+        n,
+        i = -1;
+    while (++i < n) {
+      if (compare(child = d3_layout_treeSearch(children[i], compare), node) > 0) {
+        node = child;
+      }
+    }
+  }
+  return node;
+}
+
+function d3_layout_treeRightmost(a, b) {
+  return a.x - b.x;
+}
+
+function d3_layout_treeLeftmost(a, b) {
+  return b.x - a.x;
+}
+
+function d3_layout_treeDeepest(a, b) {
+  return a.depth - b.depth;
+}
+
+function d3_layout_treeVisitAfter(node, callback) {
+  function visit(node, previousSibling) {
+    var children = node.children;
+    if (children && (n = children.length)) {
+      var child,
+          previousChild = null,
+          i = -1,
+          n;
+      while (++i < n) {
+        child = children[i];
+        visit(child, previousChild);
+        previousChild = child;
+      }
+    }
+    callback(node, previousSibling);
+  }
+  visit(node, null);
+}
+
+function d3_layout_treeShift(node) {
+  var shift = 0,
+      change = 0,
+      children = node.children,
+      i = children.length,
+      child;
+  while (--i >= 0) {
+    child = children[i]._tree;
+    child.prelim += shift;
+    child.mod += shift;
+    shift += child.shift + (change += child.change);
+  }
+}
+
+function d3_layout_treeMove(ancestor, node, shift) {
+  ancestor = ancestor._tree;
+  node = node._tree;
+  var change = shift / (node.number - ancestor.number);
+  ancestor.change += change;
+  node.change -= change;
+  node.shift += shift;
+  node.prelim += shift;
+  node.mod += shift;
+}
+
+function d3_layout_treeAncestor(vim, node, ancestor) {
+  return vim._tree.ancestor.parent == node.parent
+      ? vim._tree.ancestor
+      : ancestor;
+}