mediawiki-extensions-Multim.../resources/mmv/provider/mmv.provider.Image.js
Gilles Dubuc 6e127b25e2 Preload prev/next images
When the lightbox is opened, or prev/next pressed, preloads the
previous/next N images.

Technical debt introduced:
* initialization is a mess, with the viewer and the interface
  randomly setting properties on each other in different phases of
  execution. That got in the way and I shuffled things around
  until they worked, which is obviously not the way to have a
  robust system, but hopefully it will get scrapped soon anyway
  in favor of a clean top-down dependency injection.

Change-Id: Idcb5c40de1ac0b3e482decd66e56c4de8ec71b6b
Mingle: https://wikimedia.mingle.thoughtworks.com/projects/multimedia/cards/155
2014-02-13 10:52:40 +01:00

69 lines
1.8 KiB
JavaScript

/*
* This file is part of the MediaWiki extension MultimediaViewer.
*
* MultimediaViewer is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 2 of the License, or
* (at your option) any later version.
*
* MultimediaViewer is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with MultimediaViewer. If not, see <http://www.gnu.org/licenses/>.
*/
( function ( mw, $ ) {
/**
* @class mw.mmv.provider.Image
* Loads an image.
*/
function Image() {
/**
* @property {mw.mmv.performance}
* @private
*/
this.performance = new mw.mmv.performance();
/**
* AJAX call cache.
* @property {Object.<string, jQuery.Promise>} cache
* @protected
*/
this.cache = {};
}
/**
* @method
* Loads an image and returns it.
* @param {string} url
* @return {jQuery.Promise.<HTMLImageElement>} a promise which resolves to the image object
*/
Image.prototype.get = function( url ) {
var img = new window.Image(),
cacheKey = url,
deferred;
if ( !this.cache[cacheKey] ) {
deferred = $.Deferred();
this.cache[cacheKey] = deferred.promise();
this.performance.record( 'image', url ).then( function() {
img.src = url;
img.onload = function() {
deferred.resolve( img );
};
img.onerror = function() {
deferred.reject( 'could not load image from ' + url );
};
} );
}
return this.cache[cacheKey];
};
mw.mmv.provider.Image = Image;
}( mediaWiki, jQuery ) );