Network: force array order when sorting hierarchical levels (#3576)

* Network: force array order when sorting hierarchical levels

Fixes #340r34.

If coordinates are not available to sort within a hierarchical level, sort to array order instead.

The previous fix on this issue was not good enough to circumvent this quirk in the chromium sorting. This should bury it.

* Added TimSort for sorting in DirectionStrategy

* Added TimSort to LayoutEngine

* Fixed typo

lib/network/modules/LayoutEngine.js

@@ -1,4 +1,3 @@
-'use strict';
 /**
  * There's a mix-up with terms in the code. Following are the formal definitions:
  *
@@ -30,6 +29,8 @@
  * The layout is a way to arrange the nodes in the view; this can be done
  * on non-hierarchical networks as well. The converse is also possible.
  */
+'use strict';
+var TimSort =  require('timsort');
 let util = require('../../util');
 var NetworkUtil = require('../NetworkUtil').default;
 var {HorizontalStrategy, VerticalStrategy} = require('./components/DirectionStrategy.js');
@@ -1422,7 +1423,7 @@ class LayoutEngine {
       result.push(Number(size));
     });
 
-    result.sort(function(a, b) {
+    TimSort.sort(result, function(a, b) {
       return b - a;
     });
 

lib/network/modules/components/DirectionStrategy.js

@@ -3,6 +3,7 @@
  *
  * Strategy pattern for usage of direction methods for hierarchical layouts.
  */
+var TimSort =  require('timsort');
 
 
 /**
@@ -87,6 +88,15 @@ class DirectionInterface {
   /**
    * Sort array of nodes on the unfixed coordinates.
    *
+   * **Note:** chrome has non-stable sorting implementation, which
+   * has a tendency to change the order of the array items,
+   * even if the custom sort function returns 0.
+   *
+   * For this reason, an external sort implementation is used,
+   * which has the added benefit of being faster than the standard
+   * platforms implementation. This has been verified on `node.js`,
+   * `firefox` and `chrome` (all linux).
+   *
    * @param {Array.<Node>} nodeArray array of nodes to sort
    */
   sort(nodeArray) { this.fake_use(nodeArray); this.abstract(); }
@@ -156,9 +166,7 @@ class VerticalStrategy extends DirectionInterface {
 
   /** @inheritdoc */
   sort(nodeArray) {
-    nodeArray.sort(function(a, b) {
-      // Test on 'undefined' takes care of divergent behaviour in chrome
-      if (a.x === undefined || b.x === undefined) return 0;   // THIS HAPPENS
+    TimSort.sort(nodeArray, function(a, b) {
       return a.x - b.x;
     });
   }
@@ -221,9 +229,7 @@ class HorizontalStrategy extends DirectionInterface {
 
   /** @inheritdoc */
   sort(nodeArray) {
-    nodeArray.sort(function(a, b) {
-      // Test on 'undefined' takes care of divergent behaviour in chrome
-      if (a.y === undefined || b.y === undefined) return 0;   // THIS HAPPENS
+    TimSort.sort(nodeArray, function(a, b) {
       return a.y - b.y;
     });
   }

package.json

@@ -38,7 +38,8 @@
     "hammerjs": "^2.0.8",
     "keycharm": "^0.2.0",
     "moment": "^2.18.1",
-    "propagating-hammerjs": "^1.4.6"
+    "propagating-hammerjs": "^1.4.6",
+    "timsort": "^0.3.0"
   },
   "devDependencies": {
     "async": "^2.5.0",