fix tooltip data order for stacked charts

src/tooltip.js

@@ -29,15 +29,24 @@ c3_chart_internal_fn.getTooltipContent = function (d, defaultTitleFormat, defaul
         titleFormat = config.tooltip_format_title || defaultTitleFormat,
         nameFormat = config.tooltip_format_name || function (name) { return name; },
         valueFormat = config.tooltip_format_value || defaultValueFormat,
-        text, i, title, value, name, bgcolor;
-    
-    if (config.data_order === 'desc') {
+        text, i, title, value, name, bgcolor,
+	orderAsc = $$.isOrderAsc(), orderDesc = $$.isOrderDesc();
+     
+    if (config.data_groups.length === 0) {
 	d.sort(function(a,b){
-	    return b.value-a.value;
+	    return orderAsc ? a.value - b.value : b.value - a.value;
 	});
-    } else if (config.data_order === 'asc') {
-	d.sort(function(a,b){
-	    return a.value-b.value;
+    } else {
+	var targets = $$.orderTargets($$.data.targets);
+	var data_targets = targets.map(function (i) {
+	    return i.id;
+	});
+	d.sort(function(a, b) {
+	    if (a.value > 0 && b.value > 0) {
+		return orderAsc ? data_targets.indexOf(a.id) - data_targets.indexOf(b.id) : data_targets.indexOf(b.id) - data_targets.indexOf(a.id);
+	    } else {
+		return orderAsc ? a.value - b.value : b.value - a.value;
+	    }
 	});
     }