From bb942aa9b604b93c15048003795f4df77d9bb008 Mon Sep 17 00:00:00 2001
From: Bryan Housel <bryan@mapbox.com>
Date: Fri, 9 Sep 2016 23:20:48 -0400
Subject: [PATCH] Add only a single defs element to surface

---
 modules/svg/layers.js   | 8 ++++++--
 test/spec/svg/layers.js | 7 +++++++
 2 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/modules/svg/layers.js b/modules/svg/layers.js
index e43cc53f7..998c789d2 100644
--- a/modules/svg/layers.js
+++ b/modules/svg/layers.js
@@ -29,8 +29,12 @@ export function Layers(projection, context) {
             .attr('class', 'surface')
             .merge(svg);
 
-        svg
-            .append('defs');
+        var defs = svg.selectAll('.surface-defs')
+            .data([0]);
+
+        defs.enter()
+            .append('defs')
+            .attr('class', 'surface-defs');
 
         var groups = svg.selectAll('.data-layer')
             .data(layers);
diff --git a/test/spec/svg/layers.js b/test/spec/svg/layers.js
index ca79b45a2..82db8c3fd 100644
--- a/test/spec/svg/layers.js
+++ b/test/spec/svg/layers.js
@@ -16,6 +16,13 @@ describe('iD.svg.Layers', function () {
         expect(container.selectAll('svg')).to.be.classed('surface');
     });
 
+    it('creates surface defs', function () {
+        container.call(iD.svg.Layers(projection, context));
+        var nodes = container.selectAll('svg defs').nodes();
+        expect(nodes.length).to.eql(1);
+        expect(d3.select(nodes[0])).to.be.classed('surface-defs');
+    });
+
     it('creates default data layers', function () {
         container.call(iD.svg.Layers(projection, context));
         var nodes = container.selectAll('svg .data-layer').nodes();