From bedda42c3e281f0279f27f6dc8d0d8a05fdca145 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Attila=20Ber=C3=A9nyi?= <aberenyi@gislab.hu>
Date: Fri, 29 Apr 2016 15:37:28 +0200
Subject: [PATCH] Ignore duplicate attributions.

See https://github.com/openlayers/ol3/issues/5297
---
 src/ol/control/attribution.js | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/src/ol/control/attribution.js b/src/ol/control/attribution.js
index 0963d4060f..2fce9c8735 100644
--- a/src/ol/control/attribution.js
+++ b/src/ol/control/attribution.js
@@ -182,11 +182,21 @@ ol.control.Attribution.prototype.getSourceAttributions = function(frameState) {
       } else {
         intersectsTileRange = false;
       }
+      var attributionAlreadyAdded = false;
       if (intersectsTileRange) {
         if (sourceAttributionKey in hiddenAttributions) {
           delete hiddenAttributions[sourceAttributionKey];
         }
-        attributions[sourceAttributionKey] = sourceAttribution;
+        for (var existingKey in attributions) {
+          if (attributions.hasOwnProperty(existingKey)) {
+            if (attributions[existingKey].getHTML() === sourceAttribution.getHTML()) {
+              attributionAlreadyAdded = true;
+            }
+          }
+        }
+        if (!attributionAlreadyAdded) {
+          attributions[sourceAttributionKey] = sourceAttribution;
+        }
       } else {
         hiddenAttributions[sourceAttributionKey] = sourceAttribution;
       }