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/* Copyright (c) 2006-2013 by OpenLayers Contributors (see authors.txt for
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* full list of contributors). Published under the 2-clause BSD license.
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* See license.txt in the OpenLayers distribution or repository for the
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* full text of the license. */
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/**
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* @requires OpenLayers/Control.js
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* @requires OpenLayers/Request.js
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* @requires OpenLayers/Console.js
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*/
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/**
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* Class: OpenLayers.Control.CacheWrite
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* A control for caching image tiles in the browser's local storage. The
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* <OpenLayers.Control.CacheRead> control is used to fetch and use the cached
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* tile images.
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*
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* Note: Before using this control on any layer that is not your own, make sure
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* that the terms of service of the tile provider allow local storage of tiles.
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*
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* Inherits from:
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* - <OpenLayers.Control>
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*/
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OpenLayers.Control.CacheWrite = OpenLayers.Class(OpenLayers.Control, {
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/**
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* APIProperty: events
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* {<OpenLayers.Events>} Events instance for listeners and triggering
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* control specific events.
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*
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* To register events in the constructor, configure <eventListeners>.
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*
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* Register a listener for a particular event with the following syntax:
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* (code)
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* control.events.register(type, obj, listener);
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* (end)
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*
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* Supported event types (in addition to those from <OpenLayers.Control.events>):
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* cachefull - Triggered when the cache is full. Listeners receive an
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* object with a tile property as first argument. The tile references
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* the tile that couldn't be cached.
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*/
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/**
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* APIProperty: eventListeners
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* {Object} Object with event listeners, keyed by event name. An optional
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* scope property defines the scope that listeners will be executed in.
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*/
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/**
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* APIProperty: layers
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* {Array(<OpenLayers.Layer.Grid>)}. Optional. If provided, caching
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* will be enabled for these layers only, otherwise for all cacheable
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* layers.
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*/
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layers: null,
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/**
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* APIProperty: imageFormat
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* {String} The image format used for caching. The default is "image/png".
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* Supported formats depend on the user agent. If an unsupported
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* <imageFormat> is provided, "image/png" will be used. For aerial
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* imagery, "image/jpeg" is recommended.
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*/
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imageFormat: "image/png",
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/**
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* Property: quotaRegEx
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* {RegExp}
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*/
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quotaRegEx: (/quota/i),
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/**
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* Constructor: OpenLayers.Control.CacheWrite
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*
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* Parameters:
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* options - {Object} Object with API properties for this control.
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*/
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/**
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* Method: setMap
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* Set the map property for the control.
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*
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* Parameters:
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* map - {<OpenLayers.Map>}
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*/
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setMap: function(map) {
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OpenLayers.Control.prototype.setMap.apply(this, arguments);
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var i, layers = this.layers || map.layers;
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for (i=layers.length-1; i>=0; --i) {
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this.addLayer({layer: layers[i]});
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}
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if (!this.layers) {
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map.events.on({
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addlayer: this.addLayer,
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removeLayer: this.removeLayer,
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scope: this
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});
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}
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},
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/**
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* Method: addLayer
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* Adds a layer to the control. Once added, tiles requested for this layer
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* will be cached.
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*
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* Parameters:
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* evt - {Object} Object with a layer property referencing an
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* <OpenLayers.Layer> instance
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*/
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addLayer: function(evt) {
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evt.layer.events.on({
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tileloadstart: this.makeSameOrigin,
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tileloaded: this.onTileLoaded,
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scope: this
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});
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},
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/**
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* Method: removeLayer
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* Removes a layer from the control. Once removed, tiles requested for this
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* layer will no longer be cached.
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*
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* Parameters:
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* evt - {Object} Object with a layer property referencing an
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* <OpenLayers.Layer> instance
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*/
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removeLayer: function(evt) {
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evt.layer.events.un({
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tileloadstart: this.makeSameOrigin,
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tileloaded: this.onTileLoaded,
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scope: this
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});
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},
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/**
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* Method: makeSameOrigin
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* If the tile does not have CORS image loading enabled and is from a
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* different origin, use OpenLayers.ProxyHost to make it a same origin url.
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*
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* Parameters:
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* evt - {<OpenLayers.Event>}
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*/
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makeSameOrigin: function(evt) {
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if (this.active) {
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var tile = evt.tile;
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if (tile instanceof OpenLayers.Tile.Image &&
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!tile.crossOriginKeyword &&
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tile.url.substr(0, 5) !== "data:") {
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var sameOriginUrl = OpenLayers.Request.makeSameOrigin(
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tile.url, OpenLayers.ProxyHost
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);
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OpenLayers.Control.CacheWrite.urlMap[sameOriginUrl] = tile.url;
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tile.url = sameOriginUrl;
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}
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}
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},
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/**
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* Method: onTileLoaded
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* Decides whether a tile can be cached and calls the cache method.
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*
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* Parameters:
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* evt - {Event}
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*/
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onTileLoaded: function(evt) {
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if (this.active && !evt.aborted &&
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evt.tile instanceof OpenLayers.Tile.Image &&
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evt.tile.url.substr(0, 5) !== 'data:') {
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this.cache({tile: evt.tile});
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delete OpenLayers.Control.CacheWrite.urlMap[evt.tile.url];
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}
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},
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/**
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* Method: cache
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* Adds a tile to the cache. When the cache is full, the "cachefull" event
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* is triggered.
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*
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* Parameters:
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* obj - {Object} Object with a tile property, tile being the
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* <OpenLayers.Tile.Image> with the data to add to the cache
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*/
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cache: function(obj) {
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if (window.localStorage) {
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var tile = obj.tile;
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try {
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var canvasContext = tile.getCanvasContext();
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if (canvasContext) {
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var urlMap = OpenLayers.Control.CacheWrite.urlMap;
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var url = urlMap[tile.url] || tile.url;
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window.localStorage.setItem(
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"olCache_" + url,
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canvasContext.canvas.toDataURL(this.imageFormat)
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);
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}
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} catch(e) {
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// local storage full or CORS violation
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var reason = e.name || e.message;
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if (reason && this.quotaRegEx.test(reason)) {
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this.events.triggerEvent("cachefull", {tile: tile});
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} else {
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OpenLayers.Console.error(e.toString());
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}
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}
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}
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},
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/**
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* Method: destroy
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* The destroy method is used to perform any clean up before the control
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* is dereferenced. Typically this is where event listeners are removed
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* to prevent memory leaks.
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*/
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destroy: function() {
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if (this.layers || this.map) {
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var i, layers = this.layers || this.map.layers;
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for (i=layers.length-1; i>=0; --i) {
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this.removeLayer({layer: layers[i]});
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}
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}
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if (this.map) {
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this.map.events.un({
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addlayer: this.addLayer,
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removeLayer: this.removeLayer,
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scope: this
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});
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}
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OpenLayers.Control.prototype.destroy.apply(this, arguments);
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},
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CLASS_NAME: "OpenLayers.Control.CacheWrite"
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});
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/**
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* APIFunction: OpenLayers.Control.CacheWrite.clearCache
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* Clears all tiles cached with <OpenLayers.Control.CacheWrite> from the cache.
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*/
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OpenLayers.Control.CacheWrite.clearCache = function() {
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if (!window.localStorage) { return; }
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var i, key;
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for (i=window.localStorage.length-1; i>=0; --i) {
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key = window.localStorage.key(i);
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if (key.substr(0, 8) === "olCache_") {
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window.localStorage.removeItem(key);
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}
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}
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};
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/**
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* Property: OpenLayers.Control.CacheWrite.urlMap
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* {Object} Mapping of same origin urls to cache url keys. Entries will be
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* deleted as soon as a tile was cached.
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*/
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OpenLayers.Control.CacheWrite.urlMap = {};
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