diff --git a/changelog/upgrade-notes.md b/changelog/upgrade-notes.md
index a534c653af..52150aea99 100644
--- a/changelog/upgrade-notes.md
+++ b/changelog/upgrade-notes.md
@@ -8,21 +8,21 @@ If you are using the layer filter of one of these methods, please note that you
 
 Old syntax:
 ```
-    map.forEachFeatureAtPixel(pixel, callback, callback_this, layerFilter_function, layerFilter_this);
+    map.forEachFeatureAtPixel(pixel, callback, callbackThis, layerFilterFn, layerFilterThis);
     
-    map.hasFeatureAtPixel(pixel, layerFilter_function, layerFilter_this);
+    map.hasFeatureAtPixel(pixel, layerFilterFn, layerFilterThis);
 ```
 
 New syntax:
 ```
-    map.forEachFeatureAtPixel(pixel, callback, callback_this, {
-        layerFilter: layerFilter_function,
-        layerFilterThis: layerFilter_this
+    map.forEachFeatureAtPixel(pixel, callback, callbackThis, {
+        layerFilter: layerFilterFn,
+        layerFilterThis: layerFilterThis
     });
     
     map.hasFeatureAtPixel(pixel, {
-        layerFilter: layerFilter_function,
-        layerFilterThis: layerFilter_this
+        layerFilter: layerFilterFn,
+        layerFilterThis: layerFilterThis
     });
 ```
 
diff --git a/externs/olx.js b/externs/olx.js
index 72ea000573..8056fa3203 100644
--- a/externs/olx.js
+++ b/externs/olx.js
@@ -303,8 +303,8 @@ olx.MapOptions.prototype.view;
 
 
 /**
- * Object literal with options for the forEachFeatureAtPixel and
- * hasFeatureAtPixel methods.
+ * Object literal with options for the {@link ol.Map#forEachFeatureAtPixel} and
+ * {@link ol.Map#hasFeatureAtPixel} methods.
  * @typedef {{layerFilter: ((function(ol.layer.Layer): boolean)|undefined),
  *    layerFilterThis: (Object|undefined),
  *    hitTolerance: (number|undefined)}}
diff --git a/src/ol/map.js b/src/ol/map.js
index 4bf8ec9dc7..d64cb9e12d 100644
--- a/src/ol/map.js
+++ b/src/ol/map.js
@@ -574,7 +574,7 @@ ol.Map.prototype.disposeInternal = function() {
  * @template S,T
  * @api stable
  */
-ol.Map.prototype.forEachFeatureAtPixel = function(pixel, callback, opt_this,opt_options) {
+ol.Map.prototype.forEachFeatureAtPixel = function(pixel, callback, opt_this, opt_options) {
   if (!this.frameState_) {
     return;
   }
diff --git a/src/ol/render/canvas/replaygroup.js b/src/ol/render/canvas/replaygroup.js
index 3614a54244..b928d8293f 100644
--- a/src/ol/render/canvas/replaygroup.js
+++ b/src/ol/render/canvas/replaygroup.js
@@ -76,6 +76,8 @@ ol.inherits(ol.render.canvas.ReplayGroup, ol.render.ReplayGroup);
 
 
 /**
+ * This cache is used for storing calculated pixel circles for increasing performance.
+ * It is a static property to allow each Replaygroup to access it.
  * @type {Object.<number, Array.<Array.<(boolean|undefined)>>>}
  * @private
  */
@@ -111,6 +113,7 @@ ol.render.canvas.ReplayGroup.fillCircleArrayRowToMiddle_ = function(array, x, y)
  * This methods creates a circle inside a fitting array. Points inside the
  * circle are marked by true, points on the outside are undefined.
  * It uses the midpoint circle algorithm.
+ * A cache is used to increase performance.
  * @param {number} radius Radius.
  * @returns {Array.<Array.<(boolean|undefined)>>} An array with marked circle points.
  * @private