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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/Control.js
*/
/**
* Class: OpenLayers.Control.CacheRead
* A control for using image tiles cached with <OpenLayers.Control.CacheWrite>
* from the browser's local storage.
*
* Inherits from:
* - <OpenLayers.Control>
*/
OpenLayers.Control.CacheRead = OpenLayers.Class(OpenLayers.Control, {
/**
* APIProperty: fetchEvent
* {String} The layer event to listen to for replacing remote resource tile
* URLs with cached data URIs. Supported values are "tileerror" (try
* remote first, fall back to cached) and "tileloadstart" (try cache
* first, fall back to remote). Default is "tileloadstart".
*
* Note that "tileerror" will not work for CORS enabled images (see
* https://developer.mozilla.org/en/CORS_Enabled_Image), i.e. layers
* configured with a <OpenLayers.Tile.Image.crossOriginKeyword> in
* <OpenLayers.Layer.Grid.tileOptions>.
*/
fetchEvent: "tileloadstart",
/**
* APIProperty: layers
* {Array(<OpenLayers.Layer.Grid>)}. Optional. If provided, only these
* layers will receive tiles from the cache.
*/
layers: null,
/**
* APIProperty: autoActivate
* {Boolean} Activate the control when it is added to a map. Default is
* true.
*/
autoActivate: true,
/**
* Constructor: OpenLayers.Control.CacheRead
*
* Parameters:
* options - {Object} Object with API properties for this control
*/
/**
* Method: setMap
* Set the map property for the control.
*
* Parameters:
* map - {<OpenLayers.Map>}
*/
setMap: function(map) {
OpenLayers.Control.prototype.setMap.apply(this, arguments);
var i, layers = this.layers || map.layers;
for (i=layers.length-1; i>=0; --i) {
this.addLayer({layer: layers[i]});
}
if (!this.layers) {
map.events.on({
addlayer: this.addLayer,
removeLayer: this.removeLayer,
scope: this
});
}
},
/**
* Method: addLayer
* Adds a layer to the control. Once added, tiles requested for this layer
* will be cached.
*
* Parameters:
* evt - {Object} Object with a layer property referencing an
* <OpenLayers.Layer> instance
*/
addLayer: function(evt) {
evt.layer.events.register(this.fetchEvent, this, this.fetch);
},
/**
* Method: removeLayer
* Removes a layer from the control. Once removed, tiles requested for this
* layer will no longer be cached.
*
* Parameters:
* evt - {Object} Object with a layer property referencing an
* <OpenLayers.Layer> instance
*/
removeLayer: function(evt) {
evt.layer.events.unregister(this.fetchEvent, this, this.fetch);
},
/**
* Method: fetch
* Listener to the <fetchEvent> event. Replaces a tile's url with a data
* URI from the cache.
*
* Parameters:
* evt - {Object} Event object with a tile property.
*/
fetch: function(evt) {
if (this.active && window.localStorage &&
evt.tile instanceof OpenLayers.Tile.Image) {
var tile = evt.tile,
url = tile.url;
// deal with modified tile urls when both CacheWrite and CacheRead
// are active
if (!tile.layer.crossOriginKeyword && OpenLayers.ProxyHost &&
url.indexOf(OpenLayers.ProxyHost) === 0) {
url = OpenLayers.Control.CacheWrite.urlMap[url];
}
var dataURI = window.localStorage.getItem("olCache_" + url);
if (dataURI) {
tile.url = dataURI;
if (evt.type === "tileerror") {
tile.setImgSrc(dataURI);
}
}
}
},
/**
* Method: destroy
* The destroy method is used to perform any clean up before the control
* is dereferenced. Typically this is where event listeners are removed
* to prevent memory leaks.
*/
destroy: function() {
if (this.layers || this.map) {
var i, layers = this.layers || this.map.layers;
for (i=layers.length-1; i>=0; --i) {
this.removeLayer({layer: layers[i]});
}
}
if (this.map) {
this.map.events.un({
addlayer: this.addLayer,
removeLayer: this.removeLayer,
scope: this
});
}
OpenLayers.Control.prototype.destroy.apply(this, arguments);
},
CLASS_NAME: "OpenLayers.Control.CacheRead"
});
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