SpriteSheetLoader.js

/*
 * SpriteSheetLoader
 * Visit http://createjs.com/ for documentation, updates and examples.
 *
 *
 * Copyright (c) 2012 gskinner.com, inc.
 *
 * Permission is hereby granted, free of charge, to any person
 * obtaining a copy of this software and associated documentation
 * files (the "Software"), to deal in the Software without
 * restriction, including without limitation the rights to use,
 * copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following
 * conditions:
 *
 * The above copyright notice and this permission notice shall be
 * included in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
 * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
 * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
 * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
 * OTHER DEALINGS IN THE SOFTWARE.
 */

/**
 * @module PreloadJS
 */

// namespace:
this.createjs = this.createjs || {};

(function () {
	"use strict";

	// constructor
	/**
	 * A loader for EaselJS SpriteSheets. Images inside the spritesheet definition are loaded before the loader
	 * completes. To load SpriteSheets using JSONP, specify a {{#crossLink "LoadItem/callback:property"}}{{/crossLink}}
	 * as part of the {{#crossLink "LoadItem"}}{{/crossLink}}. Note that the {{#crossLink "JSONLoader"}}{{/crossLink}}
	 * and {{#crossLink "JSONPLoader"}}{{/crossLink}} are higher priority loaders, so SpriteSheets <strong>must</strong>
	 * set the {{#crossLink "LoadItem"}}{{/crossLink}} {{#crossLink "LoadItem/type:property"}}{{/crossLink}} property
	 * to {{#crossLink "AbstractLoader/SPRITESHEET:property"}}{{/crossLink}}.
	 *
	 * The {{#crossLink "LoadItem"}}{{/crossLink}} {{#crossLink "LoadItem/crossOrigin:property"}}{{/crossLink}} as well
	 * as the {{#crossLink "LoadQueue's"}}{{/crossLink}} `basePath` argument and {{#crossLink "LoadQueue/_preferXHR"}}{{/crossLink}}
	 * property supplied to the {{#crossLink "LoadQueue"}}{{/crossLink}} are passed on to the sub-manifest that loads
	 * the SpriteSheet images.
	 *
	 * Note that the SpriteSheet JSON does not respect the {{#crossLink "LoadQueue/_preferXHR:property"}}{{/crossLink}}
	 * property, which should instead be determined by the presence of a {{#crossLink "LoadItem/callback:property"}}{{/crossLink}}
	 * property on the SpriteSheet load item. This is because the JSON loaded will have a different format depending on
	 * if it is loaded as JSON, so just changing `preferXHR` is not enough to change how it is loaded.
	 * @class SpriteSheetLoader
	 * @param {LoadItem|Object} loadItem
	 * @extends AbstractLoader
	 * @constructor
	 */
	function SpriteSheetLoader(loadItem, preferXHR, basePath) {
		this.AbstractLoader_constructor(loadItem, preferXHR, createjs.AbstractLoader.SPRITESHEET);

		// protected properties
		/**
		 * An internal queue which loads the SpriteSheet's images.
		 * @method _manifestQueue
		 * @type {LoadQueue}
		 * @private
		 */
		this._manifestQueue = null;
		this._basePath = basePath;
	}

	var p = createjs.extend(SpriteSheetLoader, createjs.AbstractLoader);
	var s = SpriteSheetLoader;

	// static properties
	/**
	 * The amount of progress that the manifest itself takes up.
	 * @property SPRITESHEET_PROGRESS
	 * @type {number}
	 * @default 0.25 (25%)
	 * @private
	 * @static
	 */
	s.SPRITESHEET_PROGRESS = 0.25;

	// static methods
	/**
	 * Determines if the loader can load a specific item. This loader can only load items that are of type
	 * {{#crossLink "AbstractLoader/SPRITESHEET:property"}}{{/crossLink}}
	 * @method canLoadItem
	 * @param {LoadItem|Object} item The LoadItem that a LoadQueue is trying to load.
	 * @returns {Boolean} Whether the loader can load the item.
	 * @static
	 */
	s.canLoadItem = function (item) {
		return item.type == createjs.AbstractLoader.SPRITESHEET;
	};

	// public methods
	p.destroy = function() {
		this.AbstractLoader_destroy;
		this._manifestQueue.close();
	};

	// protected methods
	p._createRequest = function() {
		var callback = this._item.callback;
		if (callback != null) {
			this._request = new createjs.JSONPLoader(this._item);
		} else {
			this._request = new createjs.JSONLoader(this._item);
		}
	};

	p.handleEvent = function (event) {
		switch (event.type) {
			case "complete":
				this._rawResult = event.target.getResult(true);
				this._result = event.target.getResult();
				this._sendProgress(s.SPRITESHEET_PROGRESS);
				this._loadManifest(this._result);
				return;
			case "progress":
				event.loaded *= s.SPRITESHEET_PROGRESS;
				this.progress = event.loaded / event.total;
				if (isNaN(this.progress) || this.progress == Infinity) { this.progress = 0; }
				this._sendProgress(event);
				return;
		}
		this.AbstractLoader_handleEvent(event);
	};

	/**
	 * Create and load the images once the SpriteSheet JSON has been loaded.
	 * @method _loadManifest
	 * @param {Object} json
	 * @private
	 */
	p._loadManifest = function (json) {
		if (json && json.images) {
			for(var i = json.images.length - 1; i >= 0; i--) {
				json.images[i] = this._basePath + json.images[i];
			}
			var queue = this._manifestQueue = new createjs.LoadQueue(this._preferXHR, this._item.path, this._item.crossOrigin);
			queue.on("complete", this._handleManifestComplete, this, true);
			queue.on("fileload", this._handleManifestFileLoad, this);
			queue.on("progress", this._handleManifestProgress, this);
			queue.on("error", this._handleManifestError, this, true);
			queue.loadManifest(json.images);
		}
	};

	/**
	 * An item from the {{#crossLink "_manifestQueue:property"}}{{/crossLink}} has completed.
	 * @method _handleManifestFileLoad
	 * @param {Event} event
	 * @private
	 */
	p._handleManifestFileLoad = function (event) {
		var image = event.result;
		if (image != null) {
			var images = this.getResult().images;
			var pos = images.indexOf(event.item.src);
			images[pos] = image;
		}
	};

	/**
	 * The images have completed loading. This triggers the {{#crossLink "AbstractLoader/complete:event"}}{{/crossLink}}
	 * {{#crossLink "Event"}}{{/crossLink}} from the SpriteSheetLoader.
	 * @method _handleManifestComplete
	 * @param {Event} event
	 * @private
	 */
	p._handleManifestComplete = function (event) {
		this._result = new createjs.SpriteSheet(this._result);
		this._loadedItems = this._manifestQueue.getItems(true);
		this._sendComplete();
	};

	/**
	 * The images {{#crossLink "LoadQueue"}}{{/crossLink}} has reported progress.
	 * @method _handleManifestProgress
	 * @param {ProgressEvent} event
	 * @private
	 */
	p._handleManifestProgress = function (event) {
		this.progress = event.progress * (1 - s.SPRITESHEET_PROGRESS) + s.SPRITESHEET_PROGRESS;
		this._sendProgress(this.progress);
	};

	/**
	 * An image has reported an error.
	 * @method _handleManifestError
	 * @param {ErrorEvent} event
	 * @private
	 */
	p._handleManifestError = function (event) {
		var newEvent = new createjs.Event("fileerror");
		newEvent.item = event.data;
		this.dispatchEvent(newEvent);
	};

	createjs.SpriteSheetLoader = createjs.promote(SpriteSheetLoader, "AbstractLoader");

}());