Improve performance for update event rects on timeseries - #553

c3.js

@@ -1572,13 +1572,20 @@
             })
         };
     };
+    c3_chart_internal_fn.updateXs = function () {
+        var $$ = this;
+        $$.xs = [];
+        $$.data.targets[0].values.forEach(function (v) {
+            $$.xs[v.index] = v.x;
+        });
+    };
     c3_chart_internal_fn.getPrevX = function (i) {
-        var $$ = this, value = $$.getValueOnIndex($$.data.targets[0].values, i - 1);
-        return value ? value.x : null;
+        var x = this.xs[i - 1];
+        return typeof x !== 'undefined' ? x : null;
     };
     c3_chart_internal_fn.getNextX = function (i) {
-        var $$ = this, value = $$.getValueOnIndex($$.data.targets[0].values, i + 1);
-        return value ? value.x : null;
+        var x = this.xs[i + 1];
+        return typeof x !== 'undefined' ? x : null;
     };
     c3_chart_internal_fn.getMaxDataCount = function () {
         var $$ = this;
@@ -2173,6 +2180,10 @@
         }
         else {
             if (($$.isCustomX() || $$.isTimeSeries()) && !$$.isCategorized()) {
+
+                // update index for x that is used by prevX and nextX
+                $$.updateXs();
+
                 rectW = function (d) {
                     var prevX = $$.getPrevX(d.index), nextX = $$.getNextX(d.index);
 

src/data.js

@@ -100,13 +100,20 @@ c3_chart_internal_fn.cloneTarget = function (target) {
         })
     };
 };
+c3_chart_internal_fn.updateXs = function () {
+    var $$ = this;
+    $$.xs = [];
+    $$.data.targets[0].values.forEach(function (v) {
+        $$.xs[v.index] = v.x;
+    });
+};
 c3_chart_internal_fn.getPrevX = function (i) {
-    var $$ = this, value = $$.getValueOnIndex($$.data.targets[0].values, i - 1);
-    return value ? value.x : null;
+    var x = this.xs[i - 1];
+    return typeof x !== 'undefined' ? x : null;
 };
 c3_chart_internal_fn.getNextX = function (i) {
-    var $$ = this, value = $$.getValueOnIndex($$.data.targets[0].values, i + 1);
-    return value ? value.x : null;
+    var x = this.xs[i + 1];
+    return typeof x !== 'undefined' ? x : null;
 };
 c3_chart_internal_fn.getMaxDataCount = function () {
     var $$ = this;

src/interaction.js

@@ -59,6 +59,10 @@ c3_chart_internal_fn.updateEventRect = function (eventRectUpdate) {
     }
     else {
         if (($$.isCustomX() || $$.isTimeSeries()) && !$$.isCategorized()) {
+
+            // update index for x that is used by prevX and nextX
+            $$.updateXs();
+
             rectW = function (d) {
                 var prevX = $$.getPrevX(d.index), nextX = $$.getNextX(d.index);