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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
* @requires OpenLayers/Filter.js
*/
/**
* Class: OpenLayers.Strategy.Filter
* Strategy for limiting features that get added to a layer by
* evaluating a filter. The strategy maintains a cache of
* all features until removeFeatures is called on the layer.
*
* Inherits from:
* - <OpenLayers.Strategy>
*/
OpenLayers.Strategy.Filter = OpenLayers.Class(OpenLayers.Strategy, {
/**
* APIProperty: filter
* {<OpenLayers.Filter>} Filter for limiting features sent to the layer.
* Use the <setFilter> method to update this filter after construction.
*/
filter: null,
/**
* Property: cache
* {Array(<OpenLayers.Feature.Vector>)} List of currently cached
* features.
*/
cache: null,
/**
* Property: caching
* {Boolean} The filter is currently caching features.
*/
caching: false,
/**
* Constructor: OpenLayers.Strategy.Filter
* Create a new filter 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.
* By default, this strategy automatically activates itself when a layer
* is added to a map.
*
* Returns:
* {Boolean} True if the strategy was successfully activated or false if
* the strategy was already active.
*/
activate: function() {
var activated = OpenLayers.Strategy.prototype.activate.apply(this, arguments);
if (activated) {
this.cache = [];
this.layer.events.on({
"beforefeaturesadded": this.handleAdd,
"beforefeaturesremoved": this.handleRemove,
scope: this
});
}
return activated;
},
/**
* APIMethod: deactivate
* Deactivate the strategy. Clear the feature cache.
*
* Returns:
* {Boolean} True if the strategy was successfully deactivated or false if
* the strategy was already inactive.
*/
deactivate: function() {
this.cache = null;
if (this.layer && this.layer.events) {
this.layer.events.un({
"beforefeaturesadded": this.handleAdd,
"beforefeaturesremoved": this.handleRemove,
scope: this
});
}
return OpenLayers.Strategy.prototype.deactivate.apply(this, arguments);
},
/**
* Method: handleAdd
*/
handleAdd: function(event) {
if (!this.caching && this.filter) {
var features = event.features;
event.features = [];
var feature;
for (var i=0, ii=features.length; i<ii; ++i) {
feature = features[i];
if (this.filter.evaluate(feature)) {
event.features.push(feature);
} else {
this.cache.push(feature);
}
}
}
},
/**
* Method: handleRemove
*/
handleRemove: function(event) {
if (!this.caching) {
this.cache = [];
}
},
/**
* APIMethod: setFilter
* Update the filter for this strategy. This will re-evaluate
* any features on the layer and in the cache. Only features
* for which filter.evalute(feature) returns true will be
* added to the layer. Others will be cached by the strategy.
*
* Parameters:
* filter - {<OpenLayers.Filter>} A filter for evaluating features.
*/
setFilter: function(filter) {
this.filter = filter;
var previousCache = this.cache;
this.cache = [];
// look through layer for features to remove from layer
this.handleAdd({features: this.layer.features});
// cache now contains features to remove from layer
if (this.cache.length > 0) {
this.caching = true;
this.layer.removeFeatures(this.cache.slice());
this.caching = false;
}
// now look through previous cache for features to add to layer
if (previousCache.length > 0) {
var event = {features: previousCache};
this.handleAdd(event);
if (event.features.length > 0) {
// event has features to add to layer
this.caching = true;
this.layer.addFeatures(event.features);
this.caching = false;
}
}
},
CLASS_NAME: "OpenLayers.Strategy.Filter"
});