Added an option to control legend sort order.

Added a legend 'sorted' option that allows sorting of legend entries
independent of series order.  It accepts either null/false, true,
'ascending', 'descending' or a comparator function.

jquery.flot.js

@@ -51,7 +51,8 @@
                     position: "ne", // position of default legend container within plot
                     margin: 5, // distance from grid edge to default legend container within plot
                     backgroundColor: null, // null means auto-detect
-                    backgroundOpacity: 0.85 // set to 0 to avoid background
+                    backgroundOpacity: 0.85, // set to 0 to avoid background
+                    sorted: null    // default to no legend sorting
                 },
                 xaxis: {
                     show: null, // null = auto-detect, true = always, false = never
@@ -2107,18 +2108,47 @@
         }
 
         function insertLegend() {
+
             placeholder.find(".legend").remove();
 
             if (!options.legend.show)
                 return;
 
-            var fragments = [], rowStarted = false,
+            var fragments = [], entries = [], rowStarted = false,
                 lf = options.legend.labelFormatter, s, label;
+
+            // Build a list of legend entries, with each having a label and a color
+
             for (var i = 0; i < series.length; ++i) {
                 s = series[i];
-                label = s.label;
-                if (!label)
-                    continue;
+                if (s.label) {
+                    entries.push({
+                        label: lf ? lf(s.label, s) : s.label,
+                        color: s.color
+                    });
+                }
+            }
+
+            // Sort the legend using either the default or a custom comparator
+
+            if (options.legend.sorted) {
+                if ($.isFunction(options.legend.sorted)) {
+                    entries.sort(options.legend.sorted);
+                } else {
+                    var ascending = options.legend.sorted != "descending";
+                    entries.sort(function(a, b) {
+                        return a.label == b.label ? 0 : (
+                            (a.label < b.label) != ascending ? 1 : -1   // Logical XOR
+                        );
+                    });
+                }
+            }
+
+            // Generate markup for the list of entries, in their final order
+
+            for (var i = 0; i < entries.length; ++i) {
+
+                entry = entries[i];
 
                 if (i % options.legend.noColumns == 0) {
                     if (rowStarted)
@@ -2127,13 +2157,12 @@
                     rowStarted = true;
                 }
 
-                if (lf)
-                    label = lf(label, s);
-                
                 fragments.push(
-                    '<td class="legendColorBox"><div style="border:1px solid ' + options.legend.labelBoxBorderColor + ';padding:1px"><div style="width:4px;height:0;border:5px solid ' + s.color + ';overflow:hidden"></div></div></td>' +
-                    '<td class="legendLabel">' + label + '</td>');
+                    '<td class="legendColorBox"><div style="border:1px solid ' + options.legend.labelBoxBorderColor + ';padding:1px"><div style="width:4px;height:0;border:5px solid ' + entry.color + ';overflow:hidden"></div></div></td>' +
+                    '<td class="legendLabel">' + entry.label + '</td>'
+                );
             }
+
             if (rowStarted)
                 fragments.push('</tr>');