From 0a919186222712883b486aec4d4d16b29969b35a Mon Sep 17 00:00:00 2001
From: Tom MacWright <tom@macwright.org>
Date: Mon, 10 Jun 2013 17:42:31 -0700
Subject: [PATCH] Support TMS-flipped Y coordinate with {ty} replacement.

---
 js/id/renderer/background_source.js | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/js/id/renderer/background_source.js b/js/id/renderer/background_source.js
index ef17fe5da..778e0c5cc 100644
--- a/js/id/renderer/background_source.js
+++ b/js/id/renderer/background_source.js
@@ -19,6 +19,8 @@ iD.BackgroundSource.template = function(data) {
             .replace('{u}', u)
             .replace('{x}', coord[0])
             .replace('{y}', coord[1])
+            // TMS-flipped y coordinate
+            .replace('{ty}', Math.pow(2, coord[2]) - coord[1] - 1)
             .replace('{z}', coord[2])
             // JOSM style
             .replace('{zoom}', coord[2])