From b113bfea99607772d04c6c6e6258e0e256f6d8c5 Mon Sep 17 00:00:00 2001
From: Tom MacWright <tom@macwright.org>
Date: Tue, 16 Apr 2013 10:24:48 -0400
Subject: [PATCH] Prevent image filter duplication. Fixes #270

---
 lib/carto/tree/style.js                       |  6 +++--
 test/rendering/imagefilter-duplication.mml    | 15 +++++++++++
 test/rendering/imagefilter-duplication.mss    |  5 ++++
 test/rendering/imagefilter-duplication.result | 27 +++++++++++++++++++
 4 files changed, 51 insertions(+), 2 deletions(-)
 create mode 100644 test/rendering/imagefilter-duplication.mml
 create mode 100644 test/rendering/imagefilter-duplication.mss
 create mode 100644 test/rendering/imagefilter-duplication.result

diff --git a/lib/carto/tree/style.js b/lib/carto/tree/style.js
index bd3a883..059c93e 100644
--- a/lib/carto/tree/style.js
+++ b/lib/carto/tree/style.js
@@ -28,9 +28,11 @@ tree.StyleXML = function(name, attachment, definitions, env) {
     var attrs_xml = '';
 
     if (image_filters.length) {
-        attrs_xml += ' image-filters="' + image_filters.map(function(f) {
+        attrs_xml += ' image-filters="' + _.chain(image_filters)
+            // prevent identical filters from being duplicated in the style
+            .uniq(function(i) { return i.id; }).map(function(f) {
             return f.ev(env).toXML(env, true, ',', 'image-filter');
-        }).join(',') + '"';
+        }).value().join(',') + '"';
     }
 
     if (comp_op.length) {
diff --git a/test/rendering/imagefilter-duplication.mml b/test/rendering/imagefilter-duplication.mml
new file mode 100644
index 0000000..6798418
--- /dev/null
+++ b/test/rendering/imagefilter-duplication.mml
@@ -0,0 +1,15 @@
+{
+    "srs": "+proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0 +x_0=0.0 +y_0=0.0 +k=1.0 +units=m +nadgrids=@null +wktext +no_defs +over",
+    "Stylesheet": [
+        "imagefilter-duplication.mss"
+    ],
+    "Layer": [{
+        "name": "world",
+        "srs": "+proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0 +x_0=0.0 +y_0=0.0 +k=1.0 +units=m +nadgrids=@null +wktext +no_defs +over",
+        "Datasource": {
+            "file": "http://tilemill-data.s3.amazonaws.com/test_data/shape_demo.zip",
+            "type": "shape"
+        }
+    }]
+}
+
diff --git a/test/rendering/imagefilter-duplication.mss b/test/rendering/imagefilter-duplication.mss
new file mode 100644
index 0000000..0c65c5f
--- /dev/null
+++ b/test/rendering/imagefilter-duplication.mss
@@ -0,0 +1,5 @@
+#world {
+    image-filters:agg-stack-blur(3,3);
+    [zoom=2] { line-width: 3; }
+    [zoom=3] { line-width: 5; }
+}
diff --git a/test/rendering/imagefilter-duplication.result b/test/rendering/imagefilter-duplication.result
new file mode 100644
index 0000000..76b5970
--- /dev/null
+++ b/test/rendering/imagefilter-duplication.result
@@ -0,0 +1,27 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!DOCTYPE Map[]>
+<Map srs="+proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0 +x_0=0.0 +y_0=0.0 +k=1.0 +units=m +nadgrids=@null +wktext +no_defs +over" maximum-extent="-20037508.34,-20037508.34,20037508.34,20037508.34">
+
+
+<Style name="world" filter-mode="first" image-filters="agg-stack-blur(3,3)">
+  <Rule>
+    <MaxScaleDenominator>100000000</MaxScaleDenominator>
+    <MinScaleDenominator>50000000</MinScaleDenominator>
+    <LineSymbolizer stroke-width="5" />
+  </Rule>
+  <Rule>
+    <MaxScaleDenominator>200000000</MaxScaleDenominator>
+    <MinScaleDenominator>100000000</MinScaleDenominator>
+    <LineSymbolizer stroke-width="3" />
+  </Rule>
+</Style>
+<Layer name="world"
+  srs="+proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0 +x_0=0.0 +y_0=0.0 +k=1.0 +units=m +nadgrids=@null +wktext +no_defs +over">
+    <StyleName>world</StyleName>
+    <Datasource>
+       <Parameter name="file"><![CDATA[[absolute path]]]></Parameter>
+       <Parameter name="type"><![CDATA[shape]]></Parameter>
+    </Datasource>
+  </Layer>
+
+</Map>