From a53e604b5b3f8aa88916019ce13c4b24dab81fff Mon Sep 17 00:00:00 2001
From: John Firebaugh <john.firebaugh@gmail.com>
Date: Wed, 13 Feb 2013 11:57:32 -0800
Subject: [PATCH] Avoid unnecessary style recalculation

---
 js/id/renderer/map.js | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/js/id/renderer/map.js b/js/id/renderer/map.js
index 29de5489b..231a2e082 100644
--- a/js/id/renderer/map.js
+++ b/js/id/renderer/map.js
@@ -152,8 +152,12 @@ iD.Map = function(context) {
         if (resetTransform())
             difference = undefined;
 
-        surface.attr('data-zoom', ~~map.zoom());
-        tilegroup.call(background);
+        var zoom = String(~~map.zoom());
+        if (surface.attr('data-zoom') !== zoom)
+            surface.attr('data-zoom', zoom);
+
+        if (!difference)
+            tilegroup.call(background);
 
         if (map.editable()) {
             context.connection().loadTiles(projection, dimensions);