Adding paging and cluster strategies. The paging strategy intercepts a batch of features bound for the layer and caches them, giving the layer one page at a time. The cluster strategy intercepts a batch of features and groups proximate features as clusters - giving the clusters to the layer instead. Thanks for the careful review Erik. r=euzuro (see #1606).
git-svn-id: http://svn.openlayers.org/trunk/openlayers@8003 dc9f47b5-9b13-0410-9fdd-eb0c1a62fdaf
This commit is contained in:
Tim Schaub
261
lib/OpenLayers/Strategy/Cluster.js
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261
lib/OpenLayers/Strategy/Cluster.js
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/* Copyright (c) 2006-2008 MetaCarta, Inc., published under the Clear BSD
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* license. See http://svn.openlayers.org/trunk/openlayers/license.txt for the
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* full text of the license. */
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/**
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* @requires OpenLayers/Strategy.js
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*/
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/**
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* Class: OpenLayers.Strategy.Cluster
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* Strategy for vector feature clustering.
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*
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* Inherits from:
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* - <OpenLayers.Strategy>
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*/
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OpenLayers.Strategy.Cluster = OpenLayers.Class(OpenLayers.Strategy, {
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/**
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* Property: layer
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* {<OpenLayers.Layer.Vector>} The layer that this strategy is assigned to.
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*/
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layer: null,
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/**
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* APIProperty: distance
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* {Integer} Pixel distance between features that should be considered a
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* single cluster. Default is 20 pixels.
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*/
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distance: 20,
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/**
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* Property: features
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* {Array(<OpenLayers.Feature.Vector>)} Cached features.
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*/
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features: null,
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/**
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* Property: clusters
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* {Array(<OpenLayers.Feature.Vector>)} Calculated clusters.
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*/
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clusters: null,
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/**
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* Property: clustering
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* {Boolean} The strategy is currently clustering features.
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*/
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clustering: false,
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/**
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* Property: resolution
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* {Float} The resolution (map units per pixel) of the current cluster set.
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*/
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resolution: null,
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/**
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* Constructor: OpenLayers.Strategy.Cluster
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* Create a new clustering strategy.
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*
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* Parameters:
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* options - {Object} Optional object whose properties will be set on the
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* instance.
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*/
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initialize: function(options) {
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OpenLayers.Strategy.prototype.initialize.apply(this, [options]);
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},
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/**
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* APIMethod: activate
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* Activate the strategy. Register any listeners, do appropriate setup.
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*
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* Returns:
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* {Boolean} The strategy was successfully activated.
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*/
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activate: function() {
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var activated = OpenLayers.Strategy.prototype.activate.call(this);
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if(activated) {
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this.layer.events.on({
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"beforefeaturesadded": this.cacheFeatures,
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scope: this
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});
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this.layer.map.events.on({"zoomend": this.cluster, scope: this});
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}
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return activated;
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},
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/**
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* APIMethod: deactivate
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* Deactivate the strategy. Unregister any listeners, do appropriate
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* tear-down.
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*
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* Returns:
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* {Boolean} The strategy was successfully deactivated.
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*/
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deactivate: function() {
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var deactivated = OpenLayers.Strategy.prototype.deactivate.call(this);
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if(deactivated) {
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this.clearCache();
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this.layer.events.un({
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"beforefeaturesadded": this.cacheFeatures,
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scope: this
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});
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this.layer.map.events.un({"zoomend": this.cluster, scope: this});
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}
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return deactivated;
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},
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/**
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* Method: cacheFeatures
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* Cache features before they are added to the layer.
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*
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* Parameters:
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* event - {Object} The event that this was listening for. This will come
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* with a batch of features to be clustered.
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*
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* Returns:
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* {Boolean} False to stop layer from being added to the layer.
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*/
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cacheFeatures: function(event) {
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var propagate = true;
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if(!this.clustering) {
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this.clearCache();
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this.features = event.features;
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this.cluster();
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propagate = false;
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}
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return propagate;
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},
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/**
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* Method: clearCache
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* Clear out the cached features. This destroys features, assuming
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* nothing else has a reference.
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*/
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clearCache: function() {
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if(this.features) {
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for(var i=0; i<this.features.length; ++i) {
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this.features[i].destroy();
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}
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}
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this.features = null;
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},
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/**
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* Method: cluster
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* Cluster features based on some threshold distance.
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*/
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cluster: function() {
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if(this.features) {
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var resolution = this.layer.getResolution();
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if(resolution != this.resolution || !this.clustersExist()) {
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this.resolution = resolution;
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var clusters = [];
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var feature, clustered, cluster;
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for(var i=0; i<this.features.length; ++i) {
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feature = this.features[i];
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clustered = false;
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for(var j=0; j<clusters.length; ++j) {
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cluster = clusters[j];
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if(this.shouldCluster(cluster, feature)) {
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this.addToCluster(cluster, feature);
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clustered = true;
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break;
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}
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}
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if(!clustered) {
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clusters.push(this.createCluster(this.features[i]));
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}
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}
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this.layer.destroyFeatures();
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if(clusters.length > 0) {
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this.clustering = true;
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// A legitimate feature addition could occur during this
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// addFeatures call. For clustering to behave well, features
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// should be removed from a layer before requesting a new batch.
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this.layer.addFeatures(clusters);
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this.clustering = false;
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}
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this.clusters = clusters;
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}
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}
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},
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/**
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* Method: clustersExist
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* Determine whether calculated clusters are already on the layer.
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*
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* Returns:
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* {Boolean} The calculated clusters are already on the layer.
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*/
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clustersExist: function() {
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var exist = false;
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if(this.clusters && this.clusters.length > 0 &&
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this.clusters.length == this.layer.features.length) {
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exist = true;
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for(var i=0; i<this.clusters.length; ++i) {
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if(this.clusters[i] != this.layer.features[i]) {
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exist = false;
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break;
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}
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}
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}
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return exist;
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},
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/**
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* Method: shouldCluster
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* Determine whether to include a feature in a given cluster.
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*
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* Parameters:
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* cluster - {<OpenLayers.Feature.Vector>} A cluster.
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* feature - {<OpenLayers.Feature.Vector>} A feature.
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*
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* Returns:
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* {Boolean} The feature should be included in the cluster.
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*/
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shouldCluster: function(cluster, feature) {
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var cc = cluster.geometry.getBounds().getCenterLonLat();
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var fc = feature.geometry.getBounds().getCenterLonLat();
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var distance = (
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Math.sqrt(
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Math.pow((cc.lon - fc.lon), 2) + Math.pow((cc.lat - fc.lat), 2)
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) / this.resolution
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);
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return (distance <= this.distance);
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},
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/**
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* Method: addToCluster
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* Add a feature to a cluster.
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*
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* Parameters:
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* cluster - {<OpenLayers.Feature.Vector>} A cluster.
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* feature - {<OpenLayers.Feature.Vector>} A feature.
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*/
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addToCluster: function(cluster, feature) {
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cluster.cluster.push(feature);
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cluster.attributes.count += 1;
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},
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/**
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* Method: createCluster
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* Given a feature, create a cluster.
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*
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* Parameters:
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* feature - {<OpenLayers.Feature.Vector>}
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*
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* Returns:
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* {<OpenLayers.Feature.Vector>} A cluster.
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*/
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createCluster: function(feature) {
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var center = feature.geometry.getBounds().getCenterLonLat();
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var cluster = new OpenLayers.Feature.Vector(
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new OpenLayers.Geometry.Point(center.lon, center.lat),
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{count: 1}
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);
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cluster.cluster = [feature];
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return cluster;
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},
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CLASS_NAME: "OpenLayers.Strategy.Cluster"
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});
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