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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
* @requires OpenLayers/Request.js
* @requires OpenLayers/Console.js
*/
/**
* Class: OpenLayers.Control.CacheWrite
* A control for caching image tiles in the browser's local storage. The
* <OpenLayers.Control.CacheRead> control is used to fetch and use the cached
* tile images.
*
* Note: Before using this control on any layer that is not your own, make sure
* that the terms of service of the tile provider allow local storage of tiles.
*
* Inherits from:
* - <OpenLayers.Control>
*/
OpenLayers.Control.CacheWrite = OpenLayers.Class(OpenLayers.Control, {
/**
* APIProperty: events
* {<OpenLayers.Events>} Events instance for listeners and triggering
* control specific events.
*
* To register events in the constructor, configure <eventListeners>.
*
* Register a listener for a particular event with the following syntax:
* (code)
* control.events.register(type, obj, listener);
* (end)
*
* Supported event types (in addition to those from <OpenLayers.Control.events>):
* cachefull - Triggered when the cache is full. Listeners receive an
* object with a tile property as first argument. The tile references
* the tile that couldn't be cached.
*/
/**
* APIProperty: eventListeners
* {Object} Object with event listeners, keyed by event name. An optional
* scope property defines the scope that listeners will be executed in.
*/
/**
* APIProperty: layers
* {Array(<OpenLayers.Layer.Grid>)}. Optional. If provided, caching
* will be enabled for these layers only, otherwise for all cacheable
* layers.
*/
layers: null,
/**
* APIProperty: imageFormat
* {String} The image format used for caching. The default is "image/png".
* Supported formats depend on the user agent. If an unsupported
* <imageFormat> is provided, "image/png" will be used. For aerial
* imagery, "image/jpeg" is recommended.
*/
imageFormat: "image/png",
/**
* Property: quotaRegEx
* {RegExp}
*/
quotaRegEx: (/quota/i),
/**
* Constructor: OpenLayers.Control.CacheWrite
*
* 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.on({
tileloadstart: this.makeSameOrigin,
tileloaded: this.onTileLoaded,
scope: this
});
},
/**
* 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.un({
tileloadstart: this.makeSameOrigin,
tileloaded: this.onTileLoaded,
scope: this
});
},
/**
* Method: makeSameOrigin
* If the tile does not have CORS image loading enabled and is from a
* different origin, use OpenLayers.ProxyHost to make it a same origin url.
*
* Parameters:
* evt - {<OpenLayers.Event>}
*/
makeSameOrigin: function(evt) {
if (this.active) {
var tile = evt.tile;
if (tile instanceof OpenLayers.Tile.Image &&
!tile.crossOriginKeyword &&
tile.url.substr(0, 5) !== "data:") {
var sameOriginUrl = OpenLayers.Request.makeSameOrigin(
tile.url, OpenLayers.ProxyHost
);
OpenLayers.Control.CacheWrite.urlMap[sameOriginUrl] = tile.url;
tile.url = sameOriginUrl;
}
}
},
/**
* Method: onTileLoaded
* Decides whether a tile can be cached and calls the cache method.
*
* Parameters:
* evt - {Event}
*/
onTileLoaded: function(evt) {
if (this.active && !evt.aborted &&
evt.tile instanceof OpenLayers.Tile.Image &&
evt.tile.url.substr(0, 5) !== 'data:') {
this.cache({tile: evt.tile});
delete OpenLayers.Control.CacheWrite.urlMap[evt.tile.url];
}
},
/**
* Method: cache
* Adds a tile to the cache. When the cache is full, the "cachefull" event
* is triggered.
*
* Parameters:
* obj - {Object} Object with a tile property, tile being the
* <OpenLayers.Tile.Image> with the data to add to the cache
*/
cache: function(obj) {
if (window.localStorage) {
var tile = obj.tile;
try {
var canvasContext = tile.getCanvasContext();
if (canvasContext) {
var urlMap = OpenLayers.Control.CacheWrite.urlMap;
var url = urlMap[tile.url] || tile.url;
window.localStorage.setItem(
"olCache_" + url,
canvasContext.canvas.toDataURL(this.imageFormat)
);
}
} catch(e) {
// local storage full or CORS violation
var reason = e.name || e.message;
if (reason && this.quotaRegEx.test(reason)) {
this.events.triggerEvent("cachefull", {tile: tile});
} else {
OpenLayers.Console.error(e.toString());
}
}
}
},
/**
* 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.CacheWrite"
});
/**
* APIFunction: OpenLayers.Control.CacheWrite.clearCache
* Clears all tiles cached with <OpenLayers.Control.CacheWrite> from the cache.
*/
OpenLayers.Control.CacheWrite.clearCache = function() {
if (!window.localStorage) { return; }
var i, key;
for (i=window.localStorage.length-1; i>=0; --i) {
key = window.localStorage.key(i);
if (key.substr(0, 8) === "olCache_") {
window.localStorage.removeItem(key);
}
}
};
/**
* Property: OpenLayers.Control.CacheWrite.urlMap
* {Object} Mapping of same origin urls to cache url keys. Entries will be
* deleted as soon as a tile was cached.
*/
OpenLayers.Control.CacheWrite.urlMap = {};
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