/ajax/libs/jquery.lazy/0.1.10/jquery.lazy.js

/*!
 * jQuery Lazy - v0.1.10
 * http://jquery.eisbehr.de/lazy/
 *
 * Copyright 2013, Daniel 'Eisbehr' Kern
 *
 * Dual licensed under the MIT and GPL v2 licenses:
 * http://www.opensource.org/licenses/mit-license.php
 * http://www.gnu.org/licenses/gpl-2.0.html
 *
 * jQuery("img.lazy").lazy();
 */

(function($, window, document, undefined)
{
	$.fn.lazy = function(settings)
	{
		/**
		 * settings and configuration data
		 * @type {}
		 */
		var configuration = 
		{
			// general
			bind            : "load",
			threshold       : 500,
			fallbackHeight  : 2000,
			visibleOnly     : true,
			
			// delay
			delay           : -1,
			combined        : false,
			
			// attribute
			attribute       : "data-src",
			removeAttribute : true,
			
			// effect
			effect          : "show",
			effectTime      : 0,
			
			// throttle
			enableThrottle  : false,
			throttle        : 250,
			
			// callback
			beforeLoad      : null,
			onLoad          : null,
			afterLoad       : null,
			onError         : null
		};
		
		// overwrite configuration with custom user settings
		if( settings ) $.extend(configuration, settings);
		
		// all given items by jQuery selector
		var items = this;
		
		// on first page load get initial images
		if( configuration.bind == "load" ) $(window).load(_init);
		
		// if event driven don't wait for page loading
		else if( configuration.bind == "event" ) _init();
		
		// bind error callback to images if wanted
		if( configuration.onError ) items.bind("error", function() { configuration.onError($(this)); });
        
		/**
		 * lazyLoadImages(allImages)
		 * 
         * the 'lazy magic'
		 * check and load all needed images
		 * 
		 * @param allImages boolean
		 * @return void
		 */
		function lazyLoadImages(allImages)
		{
			if( typeof allImages != "boolean" ) allImages = false;
			
			items.each(function()
			{
				var element = $(this);
                var tag = element.prop("tagName").toLowerCase();
                
                if( _isInLoadableArea(element) || allImages )
                {
                    // the lazy magic
                    if( // image source attribute is available
                        element.attr(configuration.attribute) && 
                        // and is image tag where attribute is not equal source 
                        ((tag == "img" && element.attr(configuration.attribute) != element.attr("src")) ||
                        // or is non image tag where attribute is not equal background
                        ((tag != "img" && element.attr(configuration.attribute) != element.css("background-image"))) ) &&
                        // and is not actually loaded just before
                        !element.data("loaded") &&
                        // and is visible or visibility doesn't matter
                        (element.is(":visible") || !configuration.visibleOnly) )
                    {
                        // create image object
                        var imageObj = $(new Image());
                        
                        // copy element information to pseudo image beacuse we return this element in "onLoad" and "onError"
                        $.each(element.prop("attributes"), function(index, attr)
                        {
                            if( attr.name != "src" )
                            {
                                // i know, there is a shorter way to do the following
                                // but this is the beste worktaround for ie6/7
                                var value = element.attr(attr.name);
                                imageObj.attr(attr.name, value);
                            }
                        });
                        
                        // bind error event if wanted
                        if( configuration.onError ) imageObj.error(function() { configuration.onError(imageObj); });
                        
                        // bind after load callback to image
                        var onLoad = true;
                        imageObj.one("load", function()
                        {
                            var callable = function()
                            {
                                if( onLoad )
                                {
                                    window.setTimeout(callable, 100);
                                    return;
                                }
                                
                                // remove element from view
                                element.hide();
                                
                                // set image back to element
                                if( tag == "img" ) element.attr("src", imageObj.attr("src"));
                                else element.css("background-image", "url(" + imageObj.attr("src") + ")");
                                
                                // bring it back with some effect!
                                element[configuration.effect](configuration.effectTime);
                                
                                // remove attribute from element
                                if( configuration.removeAttribute ) element.removeAttr(configuration.attribute);
                                
                                // call after load event
                                if( configuration.afterLoad ) configuration.afterLoad(element);
                                
                                // unbind event and remove image object
                                imageObj.unbind("load");
                                imageObj.remove();
                            };
                            
                            callable();
                        });
                        
                        // trigger function before loading image
                        if( configuration.beforeLoad ) configuration.beforeLoad(element);
                        
                        // set source
                        imageObj.attr("src", element.attr(configuration.attribute));

                        // trigger function before loading image
                        if( configuration.onLoad ) configuration.onLoad(imageObj);
                        onLoad = false;
                        
                        // call after load even on cached image
                        if( imageObj.complete ) imageObj.load();
                        
                        // mark element always as loaded
                        element.data("loaded", true);
                    }
                }
			});
			
			// cleanup all items which are allready loaded
			items = $(items).filter(function()
			{
				return !$(this).data("loaded");
			});
		}
        
		/**
		 * _init()
		 *
		 * initialize lazy plugin
		 * bind loading to events or set delay time to load all images at once
		 *
		 * @return void
		 */
		function _init()
		{
			// if delay time is set load all images at once after delay time
			if( configuration.delay >= 0 ) setTimeout(function() { lazyLoadImages(true); }, configuration.delay);
			
			// if no delay is set or combine usage is active bind events
			if( configuration.delay < 0 || configuration.combined )
			{
				// load initial images
				lazyLoadImages(false);
				
				// bind lazy load functions to scroll and resize event
				$(window).bind("scroll", _throttle(configuration.throttle, lazyLoadImages));
				$(window).bind("resize", _throttle(configuration.throttle, lazyLoadImages));
			}
		}
		
		/**
		 * _isInLoadableArea(element)
		 * 
		 * check if the given element is inside the current viewport or threshold
		 * 
		 * @param element jQuery
		 * @return boolean
		 */
		function _isInLoadableArea(element)
		{
			var top = document.documentElement.scrollTop ? document.documentElement.scrollTop : document.body.scrollTop;
			return (top + _getActualHeight() + configuration.threshold) > (element.offset().top + element.height());
		}
		
		/**
		 * _getActualHeight()
		 * 
		 * try to allocate current viewport height of the browser
		 * uses fallback option when no height is found
		 * 
		 * @return number
		 */
		function _getActualHeight()
		{
			if( window.innerHeight ) return window.innerHeight;
			if( document.documentElement && document.documentElement.clientHeight ) return document.documentElement.clientHeight;
			if( document.body && document.body.clientHeight ) return document.body.clientHeight;
			if( document.body && document.body.offsetHeight ) return document.body.offsetHeight;
			
			return configuration.fallbackHeight;
		}
		
		/**
		 * _throttle(delay, call)
		 * 
		 * helper function to throttle down event triggering
		 * 
		 * @param delay integer
		 * @param call function object
		 * @return function object
		 */
		function _throttle(delay, call)
		{
			var _timeout;
			var _exec = 0;
			
			function callable()
			{
				var elapsed = +new Date() - _exec;
				
				function run()
				{
					_exec = +new Date();
					call.apply();
				}
				
				_timeout && clearTimeout(_timeout);
				
				if( elapsed > delay || !configuration.enableThrottle ) run();
				else _timeout = setTimeout(run, delay - elapsed);
			}
			
			return callable;
		}
		
		return this;
	};
	
	// make lazy a bit more caseinsensitive :)
	$.fn.Lazy = $.fn.lazy;
}
)(jQuery, window, document);