flatten first, then apply ordering, when flattening stacks

for #766, avoid concatening unordered data onto ordered data
(ordering is still kind of a weird concept when dealing with stacked bars)

fixes #772 .ordering not working for bar chart

Author: gordonwoodhull

dc.js

@@ -3259,15 +3259,9 @@ dc.stackMixin = function (_chart) {
     };
 
     function flattenStack() {
-        var groups = _chart.data();
-
-        if (groups.length) {
-            groups[0].values = _chart._computeOrderedGroups(groups[0].values);
-        }
-
-        return groups.reduce(function (all, layer) {
-            return all.concat(layer.values);
-        }, []);
+        var valueses = _chart.data().map(function (layer) { return layer.values; });
+        var flattened = Array.prototype.concat.apply([], valueses);
+        return _chart._computeOrderedGroups(flattened);
     }
 
     _chart.xAxisMin = function () {

dc.min.js

@@ -170,15 +170,9 @@ dc.stackMixin = function (_chart) {
     };
 
     function flattenStack() {
-        var groups = _chart.data();
-
-        if (groups.length) {
-            groups[0].values = _chart._computeOrderedGroups(groups[0].values);
-        }
-
-        return groups.reduce(function (all, layer) {
-            return all.concat(layer.values);
-        }, []);
+        var valueses = _chart.data().map(function (layer) { return layer.values; });
+        var flattened = Array.prototype.concat.apply([], valueses);
+        return _chart._computeOrderedGroups(flattened);
     }
 
     _chart.xAxisMin = function () {

dc.min.js.map

@@ -3259,7 +3259,13 @@ dc.stackMixin = function (_chart) {
     };
 
     function flattenStack() {
-        return _chart.data().reduce(function (all, layer) {
+        var groups = _chart.data();
+
+        if (groups.length) {
+            groups[0].values = _chart._computeOrderedGroups(groups[0].values);
+        }
+
+        return groups.reduce(function (all, layer) {
             return all.concat(layer.values);
         }, []);
     }