Merge pull request joemccann#536 from benjamin-albert/master

Fixes slow scrolling when scroll sync is enabled

public/js/user/user.controller.js

@@ -13,18 +13,26 @@ module.exports =
 
   vm.profile = userService.profile;
 
+  // TODO: Move this to out of here (perhaps to its own directive).
   var $divs = jQuery('.split-editor, .split-preview');
+  var $allowed = $divs;
   var sync = function(e) {
-    var
-      $other     = $divs.not(this).off('scroll'),
-      other      = $other[0],
-      percentage = this.scrollTop / (this.scrollHeight - this.offsetHeight);
+    var $this = jQuery(this);
 
-    other.scrollTop = Math.round(percentage * (other.scrollHeight - other.offsetHeight));
+    // Prevents slow scrolling by only allows subsequent callbacks
+    // on the element that the first scroll event was triggered on.
+    // See #516 for details.
+    if ($this.is($allowed)) {
+      var
+        other     = $divs.not(this)[0],
+        percentage = this.scrollTop / (this.scrollHeight - this.offsetHeight);
 
-    $timeout(function() {
-      $other.on('scroll', sync);
-    }, 10);
+      other.scrollTop = Math.round(percentage * (other.scrollHeight - other.offsetHeight));
+
+      $allowed = $this;
+    } else {
+      $allowed = $divs;
+    }
 
     return false;
   };