reveal.js

/*!
 * reveal.js
 * http://lab.hakim.se/reveal-js
 * MIT licensed
 *
 * Copyright (C) 2014 Hakim El Hattab, http://hakim.se
 */
(function( root, factory ) {
	if( typeof define === 'function' && define.amd ) {
		// AMD. Register as an anonymous module.
		define( function() {
			root.Reveal = factory();
			return root.Reveal;
		} );
	} else if( typeof exports === 'object' ) {
		// Node. Does not work with strict CommonJS.
		module.exports = factory();
	} else {
		// Browser globals.
		root.Reveal = factory();
	}
}( this, function() {

	'use strict';

	var Reveal;

	var SLIDES_SELECTOR = '.slides section',
		HORIZONTAL_SLIDES_SELECTOR = '.slides>section',
		VERTICAL_SLIDES_SELECTOR = '.slides>section.present>section',
		HOME_SLIDE_SELECTOR = '.slides>section:first-of-type',

		// Configurations defaults, can be overridden at initialization time
		config = {

			// The "normal" size of the presentation, aspect ratio will be preserved
			// when the presentation is scaled to fit different resolutions
			width: 960,
			height: 700,

			// Factor of the display size that should remain empty around the content
			margin: 0.1,

			// Bounds for smallest/largest possible scale to apply to content
			minScale: 0.2,
			maxScale: 1.0,

			// Display controls in the bottom right corner
			controls: true,

			// Display a presentation progress bar
			progress: true,

			// Display the page number of the current slide
			slideNumber: false,

			// Push each slide change to the browser history
			history: false,

			// Enable keyboard shortcuts for navigation
			keyboard: true,

			// Optional function that blocks keyboard events when retuning false
			keyboardCondition: null,

			// Enable the slide overview mode
			overview: true,

			// Vertical centering of slides
			center: true,

			// Enables touch navigation on devices with touch input
			touch: true,

			// Loop the presentation
			loop: false,

			// Change the presentation direction to be RTL
			rtl: false,

			// Turns fragments on and off globally
			fragments: true,

			// Flags if the presentation is running in an embedded mode,
			// i.e. contained within a limited portion of the screen
			embedded: false,

			// Number of milliseconds between automatically proceeding to the
			// next slide, disabled when set to 0, this value can be overwritten
			// by using a data-autoslide attribute on your slides
			autoSlide: 0,

			// Stop auto-sliding after user input
			autoSlideStoppable: true,

			// Enable slide navigation via mouse wheel
			mouseWheel: false,

			// Apply a 3D roll to links on hover
			rollingLinks: false,

			// Hides the address bar on mobile devices
			hideAddressBar: true,

			// Opens links in an iframe preview overlay
			previewLinks: false,

			// Exposes the reveal.js API through window.postMessage
			postMessage: true,

			// Dispatches all reveal.js events to the parent window through postMessage
			postMessageEvents: false,

			// Focuses body when page changes visiblity to ensure keyboard shortcuts work
			focusBodyOnPageVisibilityChange: true,

			// Theme (see /css/theme)
			theme: null,

			// Transition style
			transition: 'default', // none/fade/slide/convex/concave/zoom

			// Transition speed
			transitionSpeed: 'default', // default/fast/slow

			// Transition style for full page slide backgrounds
			backgroundTransition: 'default', // none/fade/slide/convex/concave/zoom

			// Parallax background image
			parallaxBackgroundImage: '', // CSS syntax, e.g. "a.jpg"

			// Parallax background size
			parallaxBackgroundSize: '', // CSS syntax, e.g. "3000px 2000px"

			// Number of slides away from the current that are visible
			viewDistance: 3,

			// Script dependencies to load
			dependencies: []

		},

		// Flags if reveal.js is loaded (has dispatched the 'ready' event)
		loaded = false,

		// The horizontal and vertical index of the currently active slide
		indexh,
		indexv,

		// The previous and current slide HTML elements
		previousSlide,
		currentSlide,

		previousBackground,

		// Slides may hold a data-state attribute which we pick up and apply
		// as a class to the body. This list contains the combined state of
		// all current slides.
		state = [],

		// The current scale of the presentation (see width/height config)
		scale = 1,

		// Cached references to DOM elements
		dom = {},

		// Features supported by the browser, see #checkCapabilities()
		features = {},

		// Client is a mobile device, see #checkCapabilities()
		isMobileDevice,

		// Throttles mouse wheel navigation
		lastMouseWheelStep = 0,

		// Delays updates to the URL due to a Chrome thumbnailer bug
		writeURLTimeout = 0,

		// Flags if the interaction event listeners are bound
		eventsAreBound = false,

		// The current auto-slide duration
		autoSlide = 0,

		// Auto slide properties
		autoSlidePlayer,
		autoSlideTimeout = 0,
		autoSlideStartTime = -1,
		autoSlidePaused = false,

		// Holds information about the currently ongoing touch input
		touch = {
			startX: 0,
			startY: 0,
			startSpan: 0,
			startCount: 0,
			captured: false,
			threshold: 40
		},

		// Holds information about the keyboard shortcuts
		keyboardShortcuts = {
			'N  ,  SPACE':			'Next slide',
			'P':					'Previous slide',
			'←  ,  H':		'Navigate left',
			'→  ,  L':		'Navigate right',
			'↑  ,  K':		'Navigate up',
			'↓  ,  J':		'Navigate down',
			'Home':					'First slide',
			'End':					'Last slide',
			'B  ,  .':				'Pause',
			'F':					'Fullscreen',
			'ESC, O':				'Slide overview'
		};

	/**
	 * Starts up the presentation if the client is capable.
	 */
	function initialize( options ) {

		checkCapabilities();

		if( !features.transforms2d && !features.transforms3d ) {
			document.body.setAttribute( 'class', 'no-transforms' );

			// Since JS won't be running any further, we need to load all
			// images that were intended to lazy load now
			var images = document.getElementsByTagName( 'img' );
			for( var i = 0, len = images.length; i < len; i++ ) {
				var image = images[i];
				if( image.getAttribute( 'data-src' ) ) {
					image.setAttribute( 'src', image.getAttribute( 'data-src' ) );
					image.removeAttribute( 'data-src' );
				}
			}

			// If the browser doesn't support core features we won't be
			// using JavaScript to control the presentation
			return;
		}

		// Cache references to key DOM elements
		dom.wrapper = document.querySelector( '.reveal' );
		dom.slides = document.querySelector( '.reveal .slides' );

		// Force a layout when the whole page, incl fonts, has loaded
		window.addEventListener( 'load', layout, false );

		var query = Reveal.getQueryHash();

		// Do not accept new dependencies via query config to avoid
		// the potential of malicious script injection
		if( typeof query['dependencies'] !== 'undefined' ) delete query['dependencies'];

		// Copy options over to our config object
		extend( config, options );
		extend( config, query );

		// Hide the address bar in mobile browsers
		hideAddressBar();

		// Loads the dependencies and continues to #start() once done
		load();

	}

	/**
	 * Inspect the client to see what it's capable of, this
	 * should only happens once per runtime.
	 */
	function checkCapabilities() {

		features.transforms3d = 'WebkitPerspective' in document.body.style ||
								'MozPerspective' in document.body.style ||
								'msPerspective' in document.body.style ||
								'OPerspective' in document.body.style ||
								'perspective' in document.body.style;

		features.transforms2d = 'WebkitTransform' in document.body.style ||
								'MozTransform' in document.body.style ||
								'msTransform' in document.body.style ||
								'OTransform' in document.body.style ||
								'transform' in document.body.style;

		features.requestAnimationFrameMethod = window.requestAnimationFrame || window.webkitRequestAnimationFrame || window.mozRequestAnimationFrame;
		features.requestAnimationFrame = typeof features.requestAnimationFrameMethod === 'function';

		features.canvas = !!document.createElement( 'canvas' ).getContext;

		isMobileDevice = navigator.userAgent.match( /(iphone|ipod|ipad|android)/gi );

	}

    /**
     * Loads the dependencies of reveal.js. Dependencies are
     * defined via the configuration option 'dependencies'
     * and will be loaded prior to starting/binding reveal.js.
     * Some dependencies may have an 'async' flag, if so they
     * will load after reveal.js has been started up.
     */
	function load() {

		var scripts = [],
			scriptsAsync = [],
			scriptsToPreload = 0;

		// Called once synchronous scripts finish loading
		function proceed() {
			if( scriptsAsync.length ) {
				// Load asynchronous scripts
				head.js.apply( null, scriptsAsync );
			}

			start();
		}

		function loadScript( s ) {
			head.ready( s.src.match( /([\w\d_\-]*)\.?js$|[^\\\/]*$/i )[0], function() {
				// Extension may contain callback functions
				if( typeof s.callback === 'function' ) {
					s.callback.apply( this );
				}

				if( --scriptsToPreload === 0 ) {
					proceed();
				}
			});
		}

		for( var i = 0, len = config.dependencies.length; i < len; i++ ) {
			var s = config.dependencies[i];

			// Load if there's no condition or the condition is truthy
			if( !s.condition || s.condition() ) {
				if( s.async ) {
					scriptsAsync.push( s.src );
				}
				else {
					scripts.push( s.src );
				}

				loadScript( s );
			}
		}

		if( scripts.length ) {
			scriptsToPreload = scripts.length;

			// Load synchronous scripts
			head.js.apply( null, scripts );
		}
		else {
			proceed();
		}

	}

	/**
	 * Starts up reveal.js by binding input events and navigating
	 * to the current URL deeplink if there is one.
	 */
	function start() {

		// Make sure we've got all the DOM elements we need
		setupDOM();

		// Listen to messages posted to this window
		setupPostMessage();

		// Resets all vertical slides so that only the first is visible
		resetVerticalSlides();

		// Updates the presentation to match the current configuration values
		configure();

		// Read the initial hash
		readURL();

		// Update all backgrounds
		updateBackground( true );

		// Notify listeners that the presentation is ready but use a 1ms
		// timeout to ensure it's not fired synchronously after #initialize()
		setTimeout( function() {
			// Enable transitions now that we're loaded
			dom.slides.classList.remove( 'no-transition' );

			loaded = true;

			dispatchEvent( 'ready', {
				'indexh': indexh,
				'indexv': indexv,
				'currentSlide': currentSlide
			} );
		}, 1 );

		// Special setup and config is required when printing to PDF
		if( isPrintingPDF() ) {
			removeEventListeners();

			// The document needs to have loaded for the PDF layout
			// measurements to be accurate
			if( document.readyState === 'complete' ) {
				setupPDF();
			}
			else {
				window.addEventListener( 'load', setupPDF );
			}
		}

	}

	/**
	 * Finds and stores references to DOM elements which are
	 * required by the presentation. If a required element is
	 * not found, it is created.
	 */
	function setupDOM() {

		// Prevent transitions while we're loading
		dom.slides.classList.add( 'no-transition' );

		// Background element
		dom.background = createSingletonNode( dom.wrapper, 'div', 'backgrounds', null );

		// Progress bar
		dom.progress = createSingletonNode( dom.wrapper, 'div', 'progress', '<span></span>' );
		dom.progressbar = dom.progress.querySelector( 'span' );

		// Arrow controls
		createSingletonNode( dom.wrapper, 'aside', 'controls',
			'<div class="navigate-left"></div>' +
			'<div class="navigate-right"></div>' +
			'<div class="navigate-up"></div>' +
			'<div class="navigate-down"></div>' );

		// Slide number
		dom.slideNumber = createSingletonNode( dom.wrapper, 'div', 'slide-number', '' );

		// State background element [DEPRECATED]
		createSingletonNode( dom.wrapper, 'div', 'state-background', null );

		// Overlay graphic which is displayed during the paused mode
		createSingletonNode( dom.wrapper, 'div', 'pause-overlay', null );

		// Cache references to elements
		dom.controls = document.querySelector( '.reveal .controls' );
		dom.theme = document.querySelector( '#theme' );

		dom.wrapper.setAttribute( 'role', 'application' );

		// There can be multiple instances of controls throughout the page
		dom.controlsLeft = toArray( document.querySelectorAll( '.navigate-left' ) );
		dom.controlsRight = toArray( document.querySelectorAll( '.navigate-right' ) );
		dom.controlsUp = toArray( document.querySelectorAll( '.navigate-up' ) );
		dom.controlsDown = toArray( document.querySelectorAll( '.navigate-down' ) );
		dom.controlsPrev = toArray( document.querySelectorAll( '.navigate-prev' ) );
		dom.controlsNext = toArray( document.querySelectorAll( '.navigate-next' ) );

		dom.statusDiv = createStatusDiv();
	}

	/**
	 * Creates a hidden div with role aria-live to announce the
	 * current slide content. Hide the div off-screen to make it
	 * available only to Assistive Technologies.
	 */
	function createStatusDiv() {

		var statusDiv = document.getElementById( 'aria-status-div' );
		if( !statusDiv ) {
			statusDiv = document.createElement( 'div' );
			statusDiv.style.position = 'absolute';
			statusDiv.style.height = '1px';
			statusDiv.style.width = '1px';
			statusDiv.style.overflow ='hidden';
			statusDiv.style.clip = 'rect( 1px, 1px, 1px, 1px )';
			statusDiv.setAttribute( 'id', 'aria-status-div' );
			statusDiv.setAttribute( 'aria-live', 'polite' );
			statusDiv.setAttribute( 'aria-atomic','true' );
			dom.wrapper.appendChild( statusDiv );
		}
		return statusDiv;

	}

	/**
	 * Configures the presentation for printing to a static
	 * PDF.
	 */
	function setupPDF() {

		var slideSize = getComputedSlideSize( window.innerWidth, window.innerHeight );

		// Dimensions of the PDF pages
		var pageWidth = Math.floor( slideSize.width * ( 1 + config.margin ) ),
			pageHeight = Math.floor( slideSize.height * ( 1 + config.margin  ) );

		// Dimensions of slides within the pages
		var slideWidth = slideSize.width,
			slideHeight = slideSize.height;

		// Let the browser know what page size we want to print
		injectStyleSheet( '@page{size:'+ pageWidth +'px '+ pageHeight +'px; margin: 0;}' );

		// Limit the size of certain elements to the dimensions of the slide
		injectStyleSheet( '.reveal img, .reveal video, .reveal iframe{max-width: '+ slideWidth +'px; max-height:'+ slideHeight +'px}' );

		document.body.classList.add( 'print-pdf' );
		document.body.style.width = pageWidth + 'px';
		document.body.style.height = pageHeight + 'px';

		// Slide and slide background layout
		toArray( dom.wrapper.querySelectorAll( SLIDES_SELECTOR ) ).forEach( function( slide ) {

			// Vertical stacks are not centred since their section
			// children will be
			if( slide.classList.contains( 'stack' ) === false ) {
				// Center the slide inside of the page, giving the slide some margin
				var left = ( pageWidth - slideWidth ) / 2,
					top = ( pageHeight - slideHeight ) / 2;

				var contentHeight = getAbsoluteHeight( slide );
				var numberOfPages = Math.max( Math.ceil( contentHeight / pageHeight ), 1 );

				// Center slides vertically
				if( numberOfPages === 1 && config.center || slide.classList.contains( 'center' ) ) {
					top = Math.max( ( pageHeight - contentHeight ) / 2, 0 );
				}

				// Position the slide inside of the page
				slide.style.left = left + 'px';
				slide.style.top = top + 'px';
				slide.style.width = slideWidth + 'px';

				// TODO Backgrounds need to be multiplied when the slide
				// stretches over multiple pages
				var background = slide.querySelector( '.slide-background' );
				if( background ) {
					background.style.width = pageWidth + 'px';
					background.style.height = ( pageHeight * numberOfPages ) + 'px';
					background.style.top = -top + 'px';
					background.style.left = -left + 'px';
				}
			}

		} );

		// Show all fragments
		toArray( dom.wrapper.querySelectorAll( SLIDES_SELECTOR + ' .fragment' ) ).forEach( function( fragment ) {
			fragment.classList.add( 'visible' );
		} );

	}

	/**
	 * Creates an HTML element and returns a reference to it.
	 * If the element already exists the existing instance will
	 * be returned.
	 */
	function createSingletonNode( container, tagname, classname, innerHTML ) {

		// Find all nodes matching the description
		var nodes = container.querySelectorAll( '.' + classname );

		// Check all matches to find one which is a direct child of
		// the specified container
		for( var i = 0; i < nodes.length; i++ ) {
			var testNode = nodes[i];
			if( testNode.parentNode === container ) {
				return testNode;
			}
		}

		// If no node was found, create it now
		var node = document.createElement( tagname );
		node.classList.add( classname );
		if( typeof innerHTML === 'string' ) {
			node.innerHTML = innerHTML;
		}
		container.appendChild( node );

		return node;

	}

	/**
	 * Creates the slide background elements and appends them
	 * to the background container. One element is created per
	 * slide no matter if the given slide has visible background.
	 */
	function createBackgrounds() {

		var printMode = isPrintingPDF();

		// Clear prior backgrounds
		dom.background.innerHTML = '';
		dom.background.classList.add( 'no-transition' );

		// Iterate over all horizontal slides
		toArray( dom.wrapper.querySelectorAll( HORIZONTAL_SLIDES_SELECTOR ) ).forEach( function( slideh ) {

			var backgroundStack;

			if( printMode ) {
				backgroundStack = createBackground( slideh, slideh );
			}
			else {
				backgroundStack = createBackground( slideh, dom.background );
			}

			// Iterate over all vertical slides
			toArray( slideh.querySelectorAll( 'section' ) ).forEach( function( slidev ) {

				if( printMode ) {
					createBackground( slidev, slidev );
				}
				else {
					createBackground( slidev, backgroundStack );
				}

				backgroundStack.classList.add( 'stack' );

			} );

		} );

		// Add parallax background if specified
		if( config.parallaxBackgroundImage ) {

			dom.background.style.backgroundImage = 'url("' + config.parallaxBackgroundImage + '")';
			dom.background.style.backgroundSize = config.parallaxBackgroundSize;

			// Make sure the below properties are set on the element - these properties are
			// needed for proper transitions to be set on the element via CSS. To remove
			// annoying background slide-in effect when the presentation starts, apply
			// these properties after short time delay
			setTimeout( function() {
				dom.wrapper.classList.add( 'has-parallax-background' );
			}, 1 );

		}
		else {

			dom.background.style.backgroundImage = '';
			dom.wrapper.classList.remove( 'has-parallax-background' );

		}

	}

	/**
	 * Creates a background for the given slide.
	 *
	 * @param {HTMLElement} slide
	 * @param {HTMLElement} container The element that the background
	 * should be appended to
	 */
	function createBackground( slide, container ) {

		var data = {
			background: slide.getAttribute( 'data-background' ),
			backgroundSize: slide.getAttribute( 'data-background-size' ),
			backgroundImage: slide.getAttribute( 'data-background-image' ),
			backgroundVideo: slide.getAttribute( 'data-background-video' ),
			backgroundColor: slide.getAttribute( 'data-background-color' ),
			backgroundRepeat: slide.getAttribute( 'data-background-repeat' ),
			backgroundPosition: slide.getAttribute( 'data-background-position' ),
			backgroundTransition: slide.getAttribute( 'data-background-transition' )
		};

		var element = document.createElement( 'div' );

		// Carry over custom classes from the slide to the background
		element.className = 'slide-background ' + slide.className.replace( /present|past|future/, '' );

		if( data.background ) {
			// Auto-wrap image urls in url(...)
			if( /^(http|file|\/\/)/gi.test( data.background ) || /\.(svg|png|jpg|jpeg|gif|bmp)$/gi.test( data.background ) ) {
				slide.setAttribute( 'data-background-image', data.background );
			}
			else {
				element.style.background = data.background;
			}
		}

		// Create a hash for this combination of background settings.
		// This is used to determine when two slide backgrounds are
		// the same.
		if( data.background || data.backgroundColor || data.backgroundImage || data.backgroundVideo ) {
			element.setAttribute( 'data-background-hash', data.background +
															data.backgroundSize +
															data.backgroundImage +
															data.backgroundVideo +
															data.backgroundColor +
															data.backgroundRepeat +
															data.backgroundPosition +
															data.backgroundTransition );
		}

		// Additional and optional background properties
		if( data.backgroundSize ) element.style.backgroundSize = data.backgroundSize;
		if( data.backgroundColor ) element.style.backgroundColor = data.backgroundColor;
		if( data.backgroundRepeat ) element.style.backgroundRepeat = data.backgroundRepeat;
		if( data.backgroundPosition ) element.style.backgroundPosition = data.backgroundPosition;
		if( data.backgroundTransition ) element.setAttribute( 'data-background-transition', data.backgroundTransition );

		container.appendChild( element );

		return element;

	}

	/**
	 * Registers a listener to postMessage events, this makes it
	 * possible to call all reveal.js API methods from another
	 * window. For example:
	 *
	 * revealWindow.postMessage( JSON.stringify({
	 *   method: 'slide',
	 *   args: [ 2 ]
	 * }), '*' );
	 */
	function setupPostMessage() {

		if( config.postMessage ) {
			window.addEventListener( 'message', function ( event ) {
				var data = event.data;

				// Make sure we're dealing with JSON
				if( data.charAt( 0 ) === '{' && data.charAt( data.length - 1 ) === '}' ) {
					data = JSON.parse( data );

					// Check if the requested method can be found
					if( data.method && typeof Reveal[data.method] === 'function' ) {
						Reveal[data.method].apply( Reveal, data.args );
					}
				}
			}, false );
		}

	}

	/**
	 * Applies the configuration settings from the config
	 * object. May be called multiple times.
	 */
	function configure( options ) {

		var numberOfSlides = dom.wrapper.querySelectorAll( SLIDES_SELECTOR ).length;

		dom.wrapper.classList.remove( config.transition );

		// New config options may be passed when this method
		// is invoked through the API after initialization
		if( typeof options === 'object' ) extend( config, options );

		// Force linear transition based on browser capabilities
		if( features.transforms3d === false ) config.transition = 'linear';

		dom.wrapper.classList.add( config.transition );

		dom.wrapper.setAttribute( 'data-transition-speed', config.transitionSpeed );
		dom.wrapper.setAttribute( 'data-background-transition', config.backgroundTransition );

		dom.controls.style.display = config.controls ? 'block' : 'none';
		dom.progress.style.display = config.progress ? 'block' : 'none';

		if( config.rtl ) {
			dom.wrapper.classList.add( 'rtl' );
		}
		else {
			dom.wrapper.classList.remove( 'rtl' );
		}

		if( config.center ) {
			dom.wrapper.classList.add( 'center' );
		}
		else {
			dom.wrapper.classList.remove( 'center' );
		}

		if( config.mouseWheel ) {
			document.addEventListener( 'DOMMouseScroll', onDocumentMouseScroll, false ); // FF
			document.addEventListener( 'mousewheel', onDocumentMouseScroll, false );
		}
		else {
			document.removeEventListener( 'DOMMouseScroll', onDocumentMouseScroll, false ); // FF
			document.removeEventListener( 'mousewheel', onDocumentMouseScroll, false );
		}

		// Rolling 3D links
		if( config.rollingLinks ) {
			enableRollingLinks();
		}
		else {
			disableRollingLinks();
		}

		// Iframe link previews
		if( config.previewLinks ) {
			enablePreviewLinks();
		}
		else {
			disablePreviewLinks();
			enablePreviewLinks( '[data-preview-link]' );
		}

		// Remove existing auto-slide controls
		if( autoSlidePlayer ) {
			autoSlidePlayer.destroy();
			autoSlidePlayer = null;
		}

		// Generate auto-slide controls if needed
		if( numberOfSlides > 1 && config.autoSlide && config.autoSlideStoppable && features.canvas && features.requestAnimationFrame ) {
			autoSlidePlayer = new Playback( dom.wrapper, function() {
				return Math.min( Math.max( ( Date.now() - autoSlideStartTime ) / autoSlide, 0 ), 1 );
			} );

			autoSlidePlayer.on( 'click', onAutoSlidePlayerClick );
			autoSlidePaused = false;
		}

		// When fragments are turned off they should be visible
		if( config.fragments === false ) {
			toArray( dom.slides.querySelectorAll( '.fragment' ) ).forEach( function( element ) {
				element.classList.add( 'visible' );
				element.classList.remove( 'current-fragment' );
			} );
		}

		// Load the theme in the config, if it's not already loaded
		if( config.theme && dom.theme ) {
			var themeURL = dom.theme.getAttribute( 'href' );
			var themeFinder = /[^\/]*?(?=\.css)/;
			var themeName = themeURL.match(themeFinder)[0];

			if(  config.theme !== themeName ) {
				themeURL = themeURL.replace(themeFinder, config.theme);
				dom.theme.setAttribute( 'href', themeURL );
			}
		}

		sync();

	}

	/**
	 * Binds all event listeners.
	 */
	function addEventListeners() {

		eventsAreBound = true;

		window.addEventListener( 'hashchange', onWindowHashChange, false );
		window.addEventListener( 'resize', onWindowResize, false );

		if( config.touch ) {
			dom.wrapper.addEventListener( 'touchstart', onTouchStart, false );
			dom.wrapper.addEventListener( 'touchmove', onTouchMove, false );
			dom.wrapper.addEventListener( 'touchend', onTouchEnd, false );

			// Support pointer-style touch interaction as well
			if( window.navigator.pointerEnabled ) {
				// IE 11 uses un-prefixed version of pointer events
				dom.wrapper.addEventListener( 'pointerdown', onPointerDown, false );
				dom.wrapper.addEventListener( 'pointermove', onPointerMove, false );
				dom.wrapper.addEventListener( 'pointerup', onPointerUp, false );
			}
			else if( window.navigator.msPointerEnabled ) {
				// IE 10 uses prefixed version of pointer events
				dom.wrapper.addEventListener( 'MSPointerDown', onPointerDown, false );
				dom.wrapper.addEventListener( 'MSPointerMove', onPointerMove, false );
				dom.wrapper.addEventListener( 'MSPointerUp', onPointerUp, false );
			}
		}

		if( config.keyboard ) {
			document.addEventListener( 'keydown', onDocumentKeyDown, false );
			document.addEventListener( 'keypress', onDocumentKeyPress, false );
		}

		if( config.progress && dom.progress ) {
			dom.progress.addEventListener( 'click', onProgressClicked, false );
		}

		if( config.focusBodyOnPageVisibilityChange ) {
			var visibilityChange;

			if( 'hidden' in document ) {
				visibilityChange = 'visibilitychange';
			}
			else if( 'msHidden' in document ) {
				visibilityChange = 'msvisibilitychange';
			}
			else if( 'webkitHidden' in document ) {
				visibilityChange = 'webkitvisibilitychange';
			}

			if( visibilityChange ) {
				document.addEventListener( visibilityChange, onPageVisibilityChange, false );
			}
		}

		[ 'touchstart', 'click' ].forEach( function( eventName ) {
			dom.controlsLeft.forEach( function( el ) { el.addEventListener( eventName, onNavigateLeftClicked, false ); } );
			dom.controlsRight.forEach( function( el ) { el.addEventListener( eventName, onNavigateRightClicked, false ); } );
			dom.controlsUp.forEach( function( el ) { el.addEventListener( eventName, onNavigateUpClicked, false ); } );
			dom.controlsDown.forEach( function( el ) { el.addEventListener( eventName, onNavigateDownClicked, false ); } );
			dom.controlsPrev.forEach( function( el ) { el.addEventListener( eventName, onNavigatePrevClicked, false ); } );
			dom.controlsNext.forEach( function( el ) { el.addEventListener( eventName, onNavigateNextClicked, false ); } );
		} );

	}

	/**
	 * Unbinds all event listeners.
	 */
	function removeEventListeners() {

		eventsAreBound = false;

		document.removeEventListener( 'keydown', onDocumentKeyDown, false );
		document.removeEventListener( 'keypress', onDocumentKeyPress, false );
		window.removeEventListener( 'hashchange', onWindowHashChange, false );
		window.removeEventListener( 'resize', onWindowResize, false );

		dom.wrapper.removeEventListener( 'touchstart', onTouchStart, false );
		dom.wrapper.removeEventListener( 'touchmove', onTouchMove, false );
		dom.wrapper.removeEventListener( 'touchend', onTouchEnd, false );

		// IE11
		if( window.navigator.pointerEnabled ) {
			dom.wrapper.removeEventListener( 'pointerdown', onPointerDown, false );
			dom.wrapper.removeEventListener( 'pointermove', onPointerMove, false );
			dom.wrapper.removeEventListener( 'pointerup', onPointerUp, false );
		}
		// IE10
		else if( window.navigator.msPointerEnabled ) {
			dom.wrapper.removeEventListener( 'MSPointerDown', onPointerDown, false );
			dom.wrapper.removeEventListener( 'MSPointerMove', onPointerMove, false );
			dom.wrapper.removeEventListener( 'MSPointerUp', onPointerUp, false );
		}

		if ( config.progress && dom.progress ) {
			dom.progress.removeEventListener( 'click', onProgressClicked, false );
		}

		[ 'touchstart', 'click' ].forEach( function( eventName ) {
			dom.controlsLeft.forEach( function( el ) { el.removeEventListener( eventName, onNavigateLeftClicked, false ); } );
			dom.controlsRight.forEach( function( el ) { el.removeEventListener( eventName, onNavigateRightClicked, false ); } );
			dom.controlsUp.forEach( function( el ) { el.removeEventListener( eventName, onNavigateUpClicked, false ); } );
			dom.controlsDown.forEach( function( el ) { el.removeEventListener( eventName, onNavigateDownClicked, false ); } );
			dom.controlsPrev.forEach( function( el ) { el.removeEventListener( eventName, onNavigatePrevClicked, false ); } );
			dom.controlsNext.forEach( function( el ) { el.removeEventListener( eventName, onNavigateNextClicked, false ); } );
		} );

	}

	/**
	 * Extend object a with the properties of object b.
	 * If there's a conflict, object b takes precedence.
	 */
	function extend( a, b ) {

		for( var i in b ) {
			a[ i ] = b[ i ];
		}

	}

	/**
	 * Converts the target object to an array.
	 */
	function toArray( o ) {

		return Array.prototype.slice.call( o );

	}

	/**
	 * Utility for deserializing a value.
	 */
	function deserialize( value ) {

		if( typeof value === 'string' ) {
			if( value === 'null' ) return null;
			else if( value === 'true' ) return true;
			else if( value === 'false' ) return false;
			else if( value.match( /^\d+$/ ) ) return parseFloat( value );
		}

		return value;

	}

	/**
	 * Measures the distance in pixels between point a
	 * and point b.