--- a/labs/openlayers/lib/OpenLayers/Strategy/Cluster.js
+++ b/labs/openlayers/lib/OpenLayers/Strategy/Cluster.js
@@ -1,1 +1,281 @@
-
+/* Copyright (c) 2006-2010 by OpenLayers Contributors (see authors.txt for 
+ * full list of contributors). Published under the Clear BSD license.  
+ * See http://svn.openlayers.org/trunk/openlayers/license.txt for the
+ * full text of the license. */
+
+/**
+ * @requires OpenLayers/Strategy.js
+ */
+
+/**
+ * Class: OpenLayers.Strategy.Cluster
+ * Strategy for vector feature clustering.
+ *
+ * Inherits from:
+ *  - <OpenLayers.Strategy>
+ */
+OpenLayers.Strategy.Cluster = OpenLayers.Class(OpenLayers.Strategy, {
+    
+    /**
+     * APIProperty: distance
+     * {Integer} Pixel distance between features that should be considered a
+     *     single cluster.  Default is 20 pixels.
+     */
+    distance: 20,
+    
+    /**
+     * APIProperty: threshold
+     * {Integer} Optional threshold below which original features will be
+     *     added to the layer instead of clusters.  For example, a threshold
+     *     of 3 would mean that any time there are 2 or fewer features in
+     *     a cluster, those features will be added directly to the layer instead
+     *     of a cluster representing those features.  Default is null (which is
+     *     equivalent to 1 - meaning that clusters may contain just one feature).
+     */
+    threshold: null,
+    
+    /**
+     * Property: features
+     * {Array(<OpenLayers.Feature.Vector>)} Cached features.
+     */
+    features: null,
+    
+    /**
+     * Property: clusters
+     * {Array(<OpenLayers.Feature.Vector>)} Calculated clusters.
+     */
+    clusters: null,
+    
+    /**
+     * Property: clustering
+     * {Boolean} The strategy is currently clustering features.
+     */
+    clustering: false,
+    
+    /**
+     * Property: resolution
+     * {Float} The resolution (map units per pixel) of the current cluster set.
+     */
+    resolution: null,
+
+    /**
+     * Constructor: OpenLayers.Strategy.Cluster
+     * Create a new clustering strategy.
+     *
+     * Parameters:
+     * options - {Object} Optional object whose properties will be set on the
+     *     instance.
+     */
+    initialize: function(options) {
+        OpenLayers.Strategy.prototype.initialize.apply(this, [options]);
+    },
+    
+    /**
+     * APIMethod: activate
+     * Activate the strategy.  Register any listeners, do appropriate setup.
+     * 
+     * Returns:
+     * {Boolean} The strategy was successfully activated.
+     */
+    activate: function() {
+        var activated = OpenLayers.Strategy.prototype.activate.call(this);
+        if(activated) {
+            this.layer.events.on({
+                "beforefeaturesadded": this.cacheFeatures,
+                "moveend": this.cluster,
+                scope: this
+            });
+        }
+        return activated;
+    },
+    
+    /**
+     * APIMethod: deactivate
+     * Deactivate the strategy.  Unregister any listeners, do appropriate
+     *     tear-down.
+     * 
+     * Returns:
+     * {Boolean} The strategy was successfully deactivated.
+     */
+    deactivate: function() {
+        var deactivated = OpenLayers.Strategy.prototype.deactivate.call(this);
+        if(deactivated) {
+            this.clearCache();
+            this.layer.events.un({
+                "beforefeaturesadded": this.cacheFeatures,
+                "moveend": this.cluster,
+                scope: this
+            });
+        }
+        return deactivated;
+    },
+    
+    /**
+     * Method: cacheFeatures
+     * Cache features before they are added to the layer.
+     *
+     * Parameters:
+     * event - {Object} The event that this was listening for.  This will come
+     *     with a batch of features to be clustered.
+     *     
+     * Returns:
+     * {Boolean} False to stop features from being added to the layer.
+     */
+    cacheFeatures: function(event) {
+        var propagate = true;
+        if(!this.clustering) {
+            this.clearCache();
+            this.features = event.features;
+            this.cluster();
+            propagate = false;
+        }
+        return propagate;
+    },
+    
+    /**
+     * Method: clearCache
+     * Clear out the cached features.
+     */
+    clearCache: function() {
+        this.features = null;
+    },
+    
+    /**
+     * Method: cluster
+     * Cluster features based on some threshold distance.
+     *
+     * Parameters:
+     * event - {Object} The event received when cluster is called as a
+     *     result of a moveend event.
+     */
+    cluster: function(event) {
+        if((!event || event.zoomChanged) && this.features) {
+            var resolution = this.layer.map.getResolution();
+            if(resolution != this.resolution || !this.clustersExist()) {
+                this.resolution = resolution;
+                var clusters = [];
+                var feature, clustered, cluster;
+                for(var i=0; i<this.features.length; ++i) {
+                    feature = this.features[i];
+                    if(feature.geometry) {
+                        clustered = false;
+                        for(var j=clusters.length-1; j>=0; --j) {
+                            cluster = clusters[j];
+                            if(this.shouldCluster(cluster, feature)) {
+                                this.addToCluster(cluster, feature);
+                                clustered = true;
+                                break;
+                            }
+                        }
+                        if(!clustered) {
+                            clusters.push(this.createCluster(this.features[i]));
+                        }
+                    }
+                }
+                this.layer.removeAllFeatures();
+                if(clusters.length > 0) {
+                    if(this.threshold > 1) {
+                        var clone = clusters.slice();
+                        clusters = [];
+                        var candidate;
+                        for(var i=0, len=clone.length; i<len; ++i) {
+                            candidate = clone[i];
+                            if(candidate.attributes.count < this.threshold) {
+                                Array.prototype.push.apply(clusters, candidate.cluster);
+                            } else {
+                                clusters.push(candidate);
+                            }
+                        }
+                    }
+                    this.clustering = true;
+                    // A legitimate feature addition could occur during this
+                    // addFeatures call.  For clustering to behave well, features
+                    // should be removed from a layer before requesting a new batch.
+                    this.layer.addFeatures(clusters);
+                    this.clustering = false;
+                }
+                this.clusters = clusters;
+            }
+        }
+    },
+    
+    /**
+     * Method: clustersExist
+     * Determine whether calculated clusters are already on the layer.
+     *
+     * Returns:
+     * {Boolean} The calculated clusters are already on the layer.
+     */
+    clustersExist: function() {
+        var exist = false;
+        if(this.clusters && this.clusters.length > 0 &&
+           this.clusters.length == this.layer.features.length) {
+            exist = true;
+            for(var i=0; i<this.clusters.length; ++i) {
+                if(this.clusters[i] != this.layer.features[i]) {
+                    exist = false;
+                    break;
+                }
+            }
+        }
+        return exist;
+    },
+    
+    /**
+     * Method: shouldCluster
+     * Determine whether to include a feature in a given cluster.
+     *
+     * Parameters:
+     * cluster - {<OpenLayers.Feature.Vector>} A cluster.
+     * feature - {<OpenLayers.Feature.Vector>} A feature.
+     *
+     * Returns:
+     * {Boolean} The feature should be included in the cluster.
+     */
+    shouldCluster: function(cluster, feature) {
+        var cc = cluster.geometry.getBounds().getCenterLonLat();
+        var fc = feature.geometry.getBounds().getCenterLonLat();
+        var distance = (
+            Math.sqrt(
+                Math.pow((cc.lon - fc.lon), 2) + Math.pow((cc.lat - fc.lat), 2)
+            ) / this.resolution
+        );
+        return (distance <= this.distance);
+    },
+    
+    /**
+     * Method: addToCluster
+     * Add a feature to a cluster.
+     *
+     * Parameters:
+     * cluster - {<OpenLayers.Feature.Vector>} A cluster.
+     * feature - {<OpenLayers.Feature.Vector>} A feature.
+     */
+    addToCluster: function(cluster, feature) {
+        cluster.cluster.push(feature);
+        cluster.attributes.count += 1;
+    },
+    
+    /**
+     * Method: createCluster
+     * Given a feature, create a cluster.
+     *
+     * Parameters:
+     * feature - {<OpenLayers.Feature.Vector>}
+     *
+     * Returns:
+     * {<OpenLayers.Feature.Vector>} A cluster.
+     */
+    createCluster: function(feature) {
+        var center = feature.geometry.getBounds().getCenterLonLat();
+        var cluster = new OpenLayers.Feature.Vector(
+            new OpenLayers.Geometry.Point(center.lon, center.lat),
+            {count: 1}
+        );
+        cluster.cluster = [feature];
+        return cluster;
+    },
+
+    CLASS_NAME: "OpenLayers.Strategy.Cluster" 
+});
+