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-/* Copyright (c) 2006-2013 by OpenLayers Contributors (see authors.txt for
- * full list of contributors). Published under the 2-clause BSD license.
- * See license.txt in the OpenLayers distribution or repository 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.
- */
-
- /**
- * 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,
- "featuresremoved": this.clearCache,
- "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,
- "featuresremoved": this.clearCache,
- "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() {
- if(!this.clustering) {
- 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.clustering = true;
- this.layer.removeAllFeatures();
- this.clustering = false;
- 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"
-});
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