michael@13: /**
michael@13:  * impress.js
michael@13:  *
michael@13:  * impress.js is a presentation tool based on the power of CSS3 transforms and transitions
michael@13:  * in modern browsers and inspired by the idea behind prezi.com.
michael@13:  *
michael@13:  *
michael@13:  * Copyright 2011-2012 Bartek Szopka (@bartaz)
michael@13:  *
michael@13:  * Released under the MIT and GPL Licenses.
michael@13:  *
michael@13:  * ------------------------------------------------
michael@13:  *  author:  Bartek Szopka
michael@13:  *  version: 0.5.3
michael@13:  *  url:     http://bartaz.github.com/impress.js/
michael@13:  *  source:  http://github.com/bartaz/impress.js/
michael@13:  */
michael@13: 
michael@13: /*jshint bitwise:true, curly:true, eqeqeq:true, forin:true, latedef:true, newcap:true,
michael@13:          noarg:true, noempty:true, undef:true, strict:true, browser:true */
michael@13: 
michael@13: // You are one of those who like to know how thing work inside?
michael@13: // Let me show you the cogs that make impress.js run...
michael@13: (function ( document, window ) {
michael@13:     'use strict';
michael@13:     
michael@13:     // HELPER FUNCTIONS
michael@13:     
michael@13:     // `pfx` is a function that takes a standard CSS property name as a parameter
michael@13:     // and returns it's prefixed version valid for current browser it runs in.
michael@13:     // The code is heavily inspired by Modernizr http://www.modernizr.com/
michael@13:     var pfx = (function () {
michael@13:         
michael@13:         var style = document.createElement('dummy').style,
michael@13:             prefixes = 'Webkit Moz O ms Khtml'.split(' '),
michael@13:             memory = {};
michael@13:         
michael@13:         return function ( prop ) {
michael@13:             if ( typeof memory[ prop ] === "undefined" ) {
michael@13:                 
michael@13:                 var ucProp  = prop.charAt(0).toUpperCase() + prop.substr(1),
michael@13:                     props   = (prop + ' ' + prefixes.join(ucProp + ' ') + ucProp).split(' ');
michael@13:                 
michael@13:                 memory[ prop ] = null;
michael@13:                 for ( var i in props ) {
michael@13:                     if ( style[ props[i] ] !== undefined ) {
michael@13:                         memory[ prop ] = props[i];
michael@13:                         break;
michael@13:                     }
michael@13:                 }
michael@13:             
michael@13:             }
michael@13:             
michael@13:             return memory[ prop ];
michael@13:         };
michael@13:     
michael@13:     })();
michael@13:     
michael@13:     // `arraify` takes an array-like object and turns it into real Array
michael@13:     // to make all the Array.prototype goodness available.
michael@13:     var arrayify = function ( a ) {
michael@13:         return [].slice.call( a );
michael@13:     };
michael@13:     
michael@13:     // `css` function applies the styles given in `props` object to the element
michael@13:     // given as `el`. It runs all property names through `pfx` function to make
michael@13:     // sure proper prefixed version of the property is used.
michael@13:     var css = function ( el, props ) {
michael@13:         var key, pkey;
michael@13:         for ( key in props ) {
michael@13:             if ( props.hasOwnProperty(key) ) {
michael@13:                 pkey = pfx(key);
michael@13:                 if ( pkey !== null ) {
michael@13:                     el.style[pkey] = props[key];
michael@13:                 }
michael@13:             }
michael@13:         }
michael@13:         return el;
michael@13:     };
michael@13:     
michael@13:     // `toNumber` takes a value given as `numeric` parameter and tries to turn
michael@13:     // it into a number. If it is not possible it returns 0 (or other value
michael@13:     // given as `fallback`).
michael@13:     var toNumber = function (numeric, fallback) {
michael@13:         return isNaN(numeric) ? (fallback || 0) : Number(numeric);
michael@13:     };
michael@13:     
michael@13:     // `byId` returns element with given `id` - you probably have guessed that ;)
michael@13:     var byId = function ( id ) {
michael@13:         return document.getElementById(id);
michael@13:     };
michael@13:     
michael@13:     // `$` returns first element for given CSS `selector` in the `context` of
michael@13:     // the given element or whole document.
michael@13:     var $ = function ( selector, context ) {
michael@13:         context = context || document;
michael@13:         return context.querySelector(selector);
michael@13:     };
michael@13:     
michael@13:     // `$$` return an array of elements for given CSS `selector` in the `context` of
michael@13:     // the given element or whole document.
michael@13:     var $$ = function ( selector, context ) {
michael@13:         context = context || document;
michael@13:         return arrayify( context.querySelectorAll(selector) );
michael@13:     };
michael@13:     
michael@13:     // `triggerEvent` builds a custom DOM event with given `eventName` and `detail` data
michael@13:     // and triggers it on element given as `el`.
michael@13:     var triggerEvent = function (el, eventName, detail) {
michael@13:         var event = document.createEvent("CustomEvent");
michael@13:         event.initCustomEvent(eventName, true, true, detail);
michael@13:         el.dispatchEvent(event);
michael@13:     };
michael@13:     
michael@13:     // `translate` builds a translate transform string for given data.
michael@13:     var translate = function ( t ) {
michael@13:         return " translate3d(" + t.x + "px," + t.y + "px," + t.z + "px) ";
michael@13:     };
michael@13:     
michael@13:     // `rotate` builds a rotate transform string for given data.
michael@13:     // By default the rotations are in X Y Z order that can be reverted by passing `true`
michael@13:     // as second parameter.
michael@13:     var rotate = function ( r, revert ) {
michael@13:         var rX = " rotateX(" + r.x + "deg) ",
michael@13:             rY = " rotateY(" + r.y + "deg) ",
michael@13:             rZ = " rotateZ(" + r.z + "deg) ";
michael@13:         
michael@13:         return revert ? rZ+rY+rX : rX+rY+rZ;
michael@13:     };
michael@13:     
michael@13:     // `scale` builds a scale transform string for given data.
michael@13:     var scale = function ( s ) {
michael@13:         return " scale(" + s + ") ";
michael@13:     };
michael@13:     
michael@13:     // `perspective` builds a perspective transform string for given data.
michael@13:     var perspective = function ( p ) {
michael@13:         return " perspective(" + p + "px) ";
michael@13:     };
michael@13:     
michael@13:     // `getElementFromHash` returns an element located by id from hash part of
michael@13:     // window location.
michael@13:     var getElementFromHash = function () {
michael@13:         // get id from url # by removing `#` or `#/` from the beginning,
michael@13:         // so both "fallback" `#slide-id` and "enhanced" `#/slide-id` will work
michael@13:         return byId( window.location.hash.replace(/^#\/?/,"") );
michael@13:     };
michael@13:     
michael@13:     // `computeWindowScale` counts the scale factor between window size and size
michael@13:     // defined for the presentation in the config.
michael@13:     var computeWindowScale = function ( config ) {
michael@13:         var hScale = window.innerHeight / config.height,
michael@13:             wScale = window.innerWidth / config.width,
michael@13:             scale = hScale > wScale ? wScale : hScale;
michael@13:         
michael@13:         if (config.maxScale && scale > config.maxScale) {
michael@13:             scale = config.maxScale;
michael@13:         }
michael@13:         
michael@13:         if (config.minScale && scale < config.minScale) {
michael@13:             scale = config.minScale;
michael@13:         }
michael@13:         
michael@13:         return scale;
michael@13:     };
michael@13:     
michael@13:     // CHECK SUPPORT
michael@13:     var body = document.body;
michael@13:     
michael@13:     var ua = navigator.userAgent.toLowerCase();
michael@13:     var impressSupported = 
michael@13:                           // browser should support CSS 3D transtorms 
michael@13:                            ( pfx("perspective") !== null ) &&
michael@13:                            
michael@13:                           // and `classList` and `dataset` APIs
michael@13:                            ( body.classList ) &&
michael@13:                            ( body.dataset ) &&
michael@13:                            
michael@13:                           // but some mobile devices need to be blacklisted,
michael@13:                           // because their CSS 3D support or hardware is not
michael@13:                           // good enough to run impress.js properly, sorry...
michael@13:                            ( ua.search(/(iphone)|(ipod)|(android)/) === -1 );
michael@13:     
michael@13:     if (!impressSupported) {
michael@13:         // we can't be sure that `classList` is supported
michael@13:         body.className += " impress-not-supported ";
michael@13:     } else {
michael@13:         body.classList.remove("impress-not-supported");
michael@13:         body.classList.add("impress-supported");
michael@13:     }
michael@13:     
michael@13:     // GLOBALS AND DEFAULTS
michael@13:     
michael@13:     // This is were the root elements of all impress.js instances will be kept.
michael@13:     // Yes, this means you can have more than one instance on a page, but I'm not
michael@13:     // sure if it makes any sense in practice ;)
michael@13:     var roots = {};
michael@13:     
michael@13:     // some default config values.
michael@13:     var defaults = {
michael@13:         width: 1024,
michael@13:         height: 768,
michael@13:         maxScale: 1,
michael@13:         minScale: 0,
michael@13:         
michael@13:         perspective: 1000,
michael@13:         
michael@13:         transitionDuration: 1000
michael@13:     };
michael@13:     
michael@13:     // it's just an empty function ... and a useless comment.
michael@13:     var empty = function () { return false; };
michael@13:     
michael@13:     // IMPRESS.JS API
michael@13:     
michael@13:     // And that's where interesting things will start to happen.
michael@13:     // It's the core `impress` function that returns the impress.js API
michael@13:     // for a presentation based on the element with given id ('impress'
michael@13:     // by default).
michael@13:     var impress = window.impress = function ( rootId ) {
michael@13:         
michael@13:         // If impress.js is not supported by the browser return a dummy API
michael@13:         // it may not be a perfect solution but we return early and avoid
michael@13:         // running code that may use features not implemented in the browser.
michael@13:         if (!impressSupported) {
michael@13:             return {
michael@13:                 init: empty,
michael@13:                 goto: empty,
michael@13:                 prev: empty,
michael@13:                 next: empty
michael@13:             };
michael@13:         }
michael@13:         
michael@13:         rootId = rootId || "impress";
michael@13:         
michael@13:         // if given root is already initialized just return the API
michael@13:         if (roots["impress-root-" + rootId]) {
michael@13:             return roots["impress-root-" + rootId];
michael@13:         }
michael@13:         
michael@13:         // data of all presentation steps
michael@13:         var stepsData = {};
michael@13:         
michael@13:         // element of currently active step
michael@13:         var activeStep = null;
michael@13:         
michael@13:         // current state (position, rotation and scale) of the presentation
michael@13:         var currentState = null;
michael@13:         
michael@13:         // array of step elements
michael@13:         var steps = null;
michael@13:         
michael@13:         // configuration options
michael@13:         var config = null;
michael@13:         
michael@13:         // scale factor of the browser window
michael@13:         var windowScale = null;        
michael@13:         
michael@13:         // root presentation elements
michael@13:         var root = byId( rootId );
michael@13:         var canvas = document.createElement("div");
michael@13:         
michael@13:         var initialized = false;
michael@13:         
michael@13:         // STEP EVENTS
michael@13:         //
michael@13:         // There are currently two step events triggered by impress.js
michael@13:         // `impress:stepenter` is triggered when the step is shown on the 
michael@13:         // screen (the transition from the previous one is finished) and
michael@13:         // `impress:stepleave` is triggered when the step is left (the
michael@13:         // transition to next step just starts).
michael@13:         
michael@13:         // reference to last entered step
michael@13:         var lastEntered = null;
michael@13:         
michael@13:         // `onStepEnter` is called whenever the step element is entered
michael@13:         // but the event is triggered only if the step is different than
michael@13:         // last entered step.
michael@13:         var onStepEnter = function (step) {
michael@13:             if (lastEntered !== step) {
michael@13:                 triggerEvent(step, "impress:stepenter");
michael@13:                 lastEntered = step;
michael@13:             }
michael@13:         };
michael@13:         
michael@13:         // `onStepLeave` is called whenever the step element is left
michael@13:         // but the event is triggered only if the step is the same as
michael@13:         // last entered step.
michael@13:         var onStepLeave = function (step) {
michael@13:             if (lastEntered === step) {
michael@13:                 triggerEvent(step, "impress:stepleave");
michael@13:                 lastEntered = null;
michael@13:             }
michael@13:         };
michael@13:         
michael@13:         // `initStep` initializes given step element by reading data from its
michael@13:         // data attributes and setting correct styles.
michael@13:         var initStep = function ( el, idx ) {
michael@13:             var data = el.dataset,
michael@13:                 step = {
michael@13:                     translate: {
michael@13:                         x: toNumber(data.x),
michael@13:                         y: toNumber(data.y),
michael@13:                         z: toNumber(data.z)
michael@13:                     },
michael@13:                     rotate: {
michael@13:                         x: toNumber(data.rotateX),
michael@13:                         y: toNumber(data.rotateY),
michael@13:                         z: toNumber(data.rotateZ || data.rotate)
michael@13:                     },
michael@13:                     scale: toNumber(data.scale, 1),
michael@13:                     el: el
michael@13:                 };
michael@13:             
michael@13:             if ( !el.id ) {
michael@13:                 el.id = "step-" + (idx + 1);
michael@13:             }
michael@13:             
michael@13:             stepsData["impress-" + el.id] = step;
michael@13:             
michael@13:             css(el, {
michael@13:                 position: "absolute",
michael@13:                 transform: "translate(-50%,-50%)" +
michael@13:                            translate(step.translate) +
michael@13:                            rotate(step.rotate) +
michael@13:                            scale(step.scale),
michael@13:                 transformStyle: "preserve-3d"
michael@13:             });
michael@13:         };
michael@13:         
michael@13:         // `init` API function that initializes (and runs) the presentation.
michael@13:         var init = function () {
michael@13:             if (initialized) { return; }
michael@13:             
michael@13:             // First we set up the viewport for mobile devices.
michael@13:             // For some reason iPad goes nuts when it is not done properly.
michael@13:             var meta = $("meta[name='viewport']") || document.createElement("meta");
michael@13:             meta.content = "width=device-width, minimum-scale=1, maximum-scale=1, user-scalable=no";
michael@13:             if (meta.parentNode !== document.head) {
michael@13:                 meta.name = 'viewport';
michael@13:                 document.head.appendChild(meta);
michael@13:             }
michael@13:             
michael@13:             // initialize configuration object
michael@13:             var rootData = root.dataset;
michael@13:             config = {
michael@13:                 width: toNumber( rootData.width, defaults.width ),
michael@13:                 height: toNumber( rootData.height, defaults.height ),
michael@13:                 maxScale: toNumber( rootData.maxScale, defaults.maxScale ),
michael@13:                 minScale: toNumber( rootData.minScale, defaults.minScale ),                
michael@13:                 perspective: toNumber( rootData.perspective, defaults.perspective ),
michael@13:                 transitionDuration: toNumber( rootData.transitionDuration, defaults.transitionDuration )
michael@13:             };
michael@13:             
michael@13:             windowScale = computeWindowScale( config );
michael@13:             
michael@13:             // wrap steps with "canvas" element
michael@13:             arrayify( root.childNodes ).forEach(function ( el ) {
michael@13:                 canvas.appendChild( el );
michael@13:             });
michael@13:             root.appendChild(canvas);
michael@13:             
michael@13:             // set initial styles
michael@13:             document.documentElement.style.height = "100%";
michael@13:             
michael@13:             css(body, {
michael@13:                 height: "100%",
michael@13:                 overflow: "hidden"
michael@13:             });
michael@13:             
michael@13:             var rootStyles = {
michael@13:                 position: "absolute",
michael@13:                 transformOrigin: "top left",
michael@13:                 transition: "all 0s ease-in-out",
michael@13:                 transformStyle: "preserve-3d"
michael@13:             };
michael@13:             
michael@13:             css(root, rootStyles);
michael@13:             css(root, {
michael@13:                 top: "50%",
michael@13:                 left: "50%",
michael@13:                 transform: perspective( config.perspective/windowScale ) + scale( windowScale )
michael@13:             });
michael@13:             css(canvas, rootStyles);
michael@13:             
michael@13:             body.classList.remove("impress-disabled");
michael@13:             body.classList.add("impress-enabled");
michael@13:             
michael@13:             // get and init steps
michael@13:             steps = $$(".step", root);
michael@13:             steps.forEach( initStep );
michael@13:             
michael@13:             // set a default initial state of the canvas
michael@13:             currentState = {
michael@13:                 translate: { x: 0, y: 0, z: 0 },
michael@13:                 rotate:    { x: 0, y: 0, z: 0 },
michael@13:                 scale:     1
michael@13:             };
michael@13:             
michael@13:             initialized = true;
michael@13:             
michael@13:             triggerEvent(root, "impress:init", { api: roots[ "impress-root-" + rootId ] });
michael@13:         };
michael@13:         
michael@13:         // `getStep` is a helper function that returns a step element defined by parameter.
michael@13:         // If a number is given, step with index given by the number is returned, if a string
michael@13:         // is given step element with such id is returned, if DOM element is given it is returned
michael@13:         // if it is a correct step element.
michael@13:         var getStep = function ( step ) {
michael@13:             if (typeof step === "number") {
michael@13:                 step = step < 0 ? steps[ steps.length + step] : steps[ step ];
michael@13:             } else if (typeof step === "string") {
michael@13:                 step = byId(step);
michael@13:             }
michael@13:             return (step && step.id && stepsData["impress-" + step.id]) ? step : null;
michael@13:         };
michael@13:         
michael@13:         // used to reset timeout for `impress:stepenter` event
michael@13:         var stepEnterTimeout = null;
michael@13:         
michael@13:         // `goto` API function that moves to step given with `el` parameter (by index, id or element),
michael@13:         // with a transition `duration` optionally given as second parameter.
michael@13:         var goto = function ( el, duration ) {
michael@13:             
michael@13:             if ( !initialized || !(el = getStep(el)) ) {
michael@13:                 // presentation not initialized or given element is not a step
michael@13:                 return false;
michael@13:             }
michael@13:             
michael@13:             // Sometimes it's possible to trigger focus on first link with some keyboard action.
michael@13:             // Browser in such a case tries to scroll the page to make this element visible
michael@13:             // (even that body overflow is set to hidden) and it breaks our careful positioning.
michael@13:             //
michael@13:             // So, as a lousy (and lazy) workaround we will make the page scroll back to the top
michael@13:             // whenever slide is selected
michael@13:             //
michael@13:             // If you are reading this and know any better way to handle it, I'll be glad to hear about it!
michael@13:             window.scrollTo(0, 0);
michael@13:             
michael@13:             var step = stepsData["impress-" + el.id];
michael@13:             
michael@13:             if ( activeStep ) {
michael@13:                 activeStep.classList.remove("active");
michael@13:                 body.classList.remove("impress-on-" + activeStep.id);
michael@13:             }
michael@13:             el.classList.add("active");
michael@13:             
michael@13:             body.classList.add("impress-on-" + el.id);
michael@13:             
michael@13:             // compute target state of the canvas based on given step
michael@13:             var target = {
michael@13:                 rotate: {
michael@13:                     x: -step.rotate.x,
michael@13:                     y: -step.rotate.y,
michael@13:                     z: -step.rotate.z
michael@13:                 },
michael@13:                 translate: {
michael@13:                     x: -step.translate.x,
michael@13:                     y: -step.translate.y,
michael@13:                     z: -step.translate.z
michael@13:                 },
michael@13:                 scale: 1 / step.scale
michael@13:             };
michael@13:             
michael@13:             // Check if the transition is zooming in or not.
michael@13:             //
michael@13:             // This information is used to alter the transition style:
michael@13:             // when we are zooming in - we start with move and rotate transition
michael@13:             // and the scaling is delayed, but when we are zooming out we start
michael@13:             // with scaling down and move and rotation are delayed.
michael@13:             var zoomin = target.scale >= currentState.scale;
michael@13:             
michael@13:             duration = toNumber(duration, config.transitionDuration);
michael@13:             var delay = (duration / 2);
michael@13:             
michael@13:             // if the same step is re-selected, force computing window scaling,
michael@13:             // because it is likely to be caused by window resize
michael@13:             if (el === activeStep) {
michael@13:                 windowScale = computeWindowScale(config);
michael@13:             }
michael@13:             
michael@13:             var targetScale = target.scale * windowScale;
michael@13:             
michael@13:             // trigger leave of currently active element (if it's not the same step again)
michael@13:             if (activeStep && activeStep !== el) {
michael@13:                 onStepLeave(activeStep);
michael@13:             }
michael@13:             
michael@13:             // Now we alter transforms of `root` and `canvas` to trigger transitions.
michael@13:             //
michael@13:             // And here is why there are two elements: `root` and `canvas` - they are
michael@13:             // being animated separately:
michael@13:             // `root` is used for scaling and `canvas` for translate and rotations.
michael@13:             // Transitions on them are triggered with different delays (to make
michael@13:             // visually nice and 'natural' looking transitions), so we need to know
michael@13:             // that both of them are finished.
michael@13:             css(root, {
michael@13:                 // to keep the perspective look similar for different scales
michael@13:                 // we need to 'scale' the perspective, too
michael@13:                 transform: perspective( config.perspective / targetScale ) + scale( targetScale ),
michael@13:                 transitionDuration: duration + "ms",
michael@13:                 transitionDelay: (zoomin ? delay : 0) + "ms"
michael@13:             });
michael@13:             
michael@13:             css(canvas, {
michael@13:                 transform: rotate(target.rotate, true) + translate(target.translate),
michael@13:                 transitionDuration: duration + "ms",
michael@13:                 transitionDelay: (zoomin ? 0 : delay) + "ms"
michael@13:             });
michael@13:             
michael@13:             // Here is a tricky part...
michael@13:             //
michael@13:             // If there is no change in scale or no change in rotation and translation, it means there was actually
michael@13:             // no delay - because there was no transition on `root` or `canvas` elements.
michael@13:             // We want to trigger `impress:stepenter` event in the correct moment, so here we compare the current
michael@13:             // and target values to check if delay should be taken into account.
michael@13:             //
michael@13:             // I know that this `if` statement looks scary, but it's pretty simple when you know what is going on
michael@13:             // - it's simply comparing all the values.
michael@13:             if ( currentState.scale === target.scale ||
michael@13:                 (currentState.rotate.x === target.rotate.x && currentState.rotate.y === target.rotate.y &&
michael@13:                  currentState.rotate.z === target.rotate.z && currentState.translate.x === target.translate.x &&
michael@13:                  currentState.translate.y === target.translate.y && currentState.translate.z === target.translate.z) ) {
michael@13:                 delay = 0;
michael@13:             }
michael@13:             
michael@13:             // store current state
michael@13:             currentState = target;
michael@13:             activeStep = el;
michael@13:             
michael@13:             // And here is where we trigger `impress:stepenter` event.
michael@13:             // We simply set up a timeout to fire it taking transition duration (and possible delay) into account.
michael@13:             //
michael@13:             // I really wanted to make it in more elegant way. The `transitionend` event seemed to be the best way
michael@13:             // to do it, but the fact that I'm using transitions on two separate elements and that the `transitionend`
michael@13:             // event is only triggered when there was a transition (change in the values) caused some bugs and 
michael@13:             // made the code really complicated, cause I had to handle all the conditions separately. And it still
michael@13:             // needed a `setTimeout` fallback for the situations when there is no transition at all.
michael@13:             // So I decided that I'd rather make the code simpler than use shiny new `transitionend`.
michael@13:             //
michael@13:             // If you want learn something interesting and see how it was done with `transitionend` go back to
michael@13:             // version 0.5.2 of impress.js: http://github.com/bartaz/impress.js/blob/0.5.2/js/impress.js
michael@13:             window.clearTimeout(stepEnterTimeout);
michael@13:             stepEnterTimeout = window.setTimeout(function() {
michael@13:                 onStepEnter(activeStep);
michael@13:             }, duration + delay);
michael@13:             
michael@13:             return el;
michael@13:         };
michael@13:         
michael@13:         // `prev` API function goes to previous step (in document order)
michael@13:         var prev = function () {
michael@13:             var prev = steps.indexOf( activeStep ) - 1;
michael@13:             prev = prev >= 0 ? steps[ prev ] : steps[ steps.length-1 ];
michael@13:             
michael@13:             return goto(prev);
michael@13:         };
michael@13:         
michael@13:         // `next` API function goes to next step (in document order)
michael@13:         var next = function () {
michael@13:             var next = steps.indexOf( activeStep ) + 1;
michael@13:             next = next < steps.length ? steps[ next ] : steps[ 0 ];
michael@13:             
michael@13:             return goto(next);
michael@13:         };
michael@13:         
michael@13:         // Adding some useful classes to step elements.
michael@13:         //
michael@13:         // All the steps that have not been shown yet are given `future` class.
michael@13:         // When the step is entered the `future` class is removed and the `present`
michael@13:         // class is given. When the step is left `present` class is replaced with
michael@13:         // `past` class.
michael@13:         //
michael@13:         // So every step element is always in one of three possible states:
michael@13:         // `future`, `present` and `past`.
michael@13:         //
michael@13:         // There classes can be used in CSS to style different types of steps.
michael@13:         // For example the `present` class can be used to trigger some custom
michael@13:         // animations when step is shown.
michael@13:         root.addEventListener("impress:init", function(){
michael@13:             // STEP CLASSES
michael@13:             steps.forEach(function (step) {
michael@13:                 step.classList.add("future");
michael@13:             });
michael@13:             
michael@13:             root.addEventListener("impress:stepenter", function (event) {
michael@13:                 event.target.classList.remove("past");
michael@13:                 event.target.classList.remove("future");
michael@13:                 event.target.classList.add("present");
michael@13:             }, false);
michael@13:             
michael@13:             root.addEventListener("impress:stepleave", function (event) {
michael@13:                 event.target.classList.remove("present");
michael@13:                 event.target.classList.add("past");
michael@13:             }, false);
michael@13:             
michael@13:         }, false);
michael@13:         
michael@13:         // Adding hash change support.
michael@13:         root.addEventListener("impress:init", function(){
michael@13:             
michael@13:             // last hash detected
michael@13:             var lastHash = "";
michael@13:             
michael@13:             // `#/step-id` is used instead of `#step-id` to prevent default browser
michael@13:             // scrolling to element in hash.
michael@13:             //
michael@13:             // And it has to be set after animation finishes, because in Chrome it
michael@13:             // makes transtion laggy.
michael@13:             // BUG: http://code.google.com/p/chromium/issues/detail?id=62820
michael@13:             root.addEventListener("impress:stepenter", function (event) {
michael@13:                 window.location.hash = lastHash = "#/" + event.target.id;
michael@13:             }, false);
michael@13:             
michael@13:             window.addEventListener("hashchange", function () {
michael@13:                 // When the step is entered hash in the location is updated
michael@13:                 // (just few lines above from here), so the hash change is 
michael@13:                 // triggered and we would call `goto` again on the same element.
michael@13:                 //
michael@13:                 // To avoid this we store last entered hash and compare.
michael@13:                 if (window.location.hash !== lastHash) {
michael@13:                     goto( getElementFromHash() );
michael@13:                 }
michael@13:             }, false);
michael@13:             
michael@13:             // START 
michael@13:             // by selecting step defined in url or first step of the presentation
michael@13:             goto(getElementFromHash() || steps[0], 0);
michael@13:         }, false);
michael@13:         
michael@13:         body.classList.add("impress-disabled");
michael@13:         
michael@13:         // store and return API for given impress.js root element
michael@13:         return (roots[ "impress-root-" + rootId ] = {
michael@13:             init: init,
michael@13:             goto: goto,
michael@13:             next: next,
michael@13:             prev: prev
michael@13:         });
michael@13: 
michael@13:     };
michael@13:     
michael@13:     // flag that can be used in JS to check if browser have passed the support test
michael@13:     impress.supported = impressSupported;
michael@13:     
michael@13: })(document, window);
michael@13: 
michael@13: // NAVIGATION EVENTS
michael@13: 
michael@13: // As you can see this part is separate from the impress.js core code.
michael@13: // It's because these navigation actions only need what impress.js provides with
michael@13: // its simple API.
michael@13: //
michael@13: // In future I think about moving it to make them optional, move to separate files
michael@13: // and treat more like a 'plugins'.
michael@13: (function ( document, window ) {
michael@13:     'use strict';
michael@13:     
michael@13:     // throttling function calls, by Remy Sharp
michael@13:     // http://remysharp.com/2010/07/21/throttling-function-calls/
michael@13:     var throttle = function (fn, delay) {
michael@13:         var timer = null;
michael@13:         return function () {
michael@13:             var context = this, args = arguments;
michael@13:             clearTimeout(timer);
michael@13:             timer = setTimeout(function () {
michael@13:                 fn.apply(context, args);
michael@13:             }, delay);
michael@13:         };
michael@13:     };
michael@13:     
michael@13:     // wait for impress.js to be initialized
michael@13:     document.addEventListener("impress:init", function (event) {
michael@13:         // Getting API from event data.
michael@13:         // So you don't event need to know what is the id of the root element
michael@13:         // or anything. `impress:init` event data gives you everything you 
michael@13:         // need to control the presentation that was just initialized.
michael@13:         var api = event.detail.api;
michael@13:         
michael@13:         // KEYBOARD NAVIGATION HANDLERS
michael@13:         
michael@13:         // Prevent default keydown action when one of supported key is pressed.
michael@13:         document.addEventListener("keydown", function ( event ) {
michael@13:             if ( event.keyCode === 9 || ( event.keyCode >= 32 && event.keyCode <= 34 ) || (event.keyCode >= 37 && event.keyCode <= 40) ) {
michael@13:                 event.preventDefault();
michael@13:             }
michael@13:         }, false);
michael@13:         
michael@13:         // Trigger impress action (next or prev) on keyup.
michael@13:         
michael@13:         // Supported keys are:
michael@13:         // [space] - quite common in presentation software to move forward
michael@13:         // [up] [right] / [down] [left] - again common and natural addition,
michael@13:         // [pgdown] / [pgup] - often triggered by remote controllers,
michael@13:         // [tab] - this one is quite controversial, but the reason it ended up on
michael@13:         //   this list is quite an interesting story... Remember that strange part
michael@13:         //   in the impress.js code where window is scrolled to 0,0 on every presentation
michael@13:         //   step, because sometimes browser scrolls viewport because of the focused element?
michael@13:         //   Well, the [tab] key by default navigates around focusable elements, so clicking
michael@13:         //   it very often caused scrolling to focused element and breaking impress.js
michael@13:         //   positioning. I didn't want to just prevent this default action, so I used [tab]
michael@13:         //   as another way to moving to next step... And yes, I know that for the sake of
michael@13:         //   consistency I should add [shift+tab] as opposite action...
michael@13:         document.addEventListener("keyup", function ( event ) {
michael@13:             if ( event.keyCode === 9 || ( event.keyCode >= 32 && event.keyCode <= 34 ) || (event.keyCode >= 37 && event.keyCode <= 40) ) {
michael@13:                 switch( event.keyCode ) {
michael@13:                     case 33: // pg up
michael@13:                     case 37: // left
michael@13:                     case 38: // up
michael@13:                              api.prev();
michael@13:                              break;
michael@13:                     case 9:  // tab
michael@13:                     case 32: // space
michael@13:                     case 34: // pg down
michael@13:                     case 39: // right
michael@13:                     case 40: // down
michael@13:                              api.next();
michael@13:                              break;
michael@13:                 }
michael@13:                 
michael@13:                 event.preventDefault();
michael@13:             }
michael@13:         }, false);
michael@13:         
michael@13:         // delegated handler for clicking on the links to presentation steps
michael@13:         document.addEventListener("click", function ( event ) {
michael@13:             // event delegation with "bubbling"
michael@13:             // check if event target (or any of its parents is a link)
michael@13:             var target = event.target;
michael@13:             while ( (target.tagName !== "A") &&
michael@13:                     (target !== document.documentElement) ) {
michael@13:                 target = target.parentNode;
michael@13:             }
michael@13:             
michael@13:             if ( target.tagName === "A" ) {
michael@13:                 var href = target.getAttribute("href");
michael@13:                 
michael@13:                 // if it's a link to presentation step, target this step
michael@13:                 if ( href && href[0] === '#' ) {
michael@13:                     target = document.getElementById( href.slice(1) );
michael@13:                 }
michael@13:             }
michael@13:             
michael@13:             if ( api.goto(target) ) {
michael@13:                 event.stopImmediatePropagation();
michael@13:                 event.preventDefault();
michael@13:             }
michael@13:         }, false);
michael@13:         
michael@13:         // delegated handler for clicking on step elements
michael@13:         document.addEventListener("click", function ( event ) {
michael@13:             var target = event.target;
michael@13:             // find closest step element that is not active
michael@13:             while ( !(target.classList.contains("step") && !target.classList.contains("active")) &&
michael@13:                     (target !== document.documentElement) ) {
michael@13:                 target = target.parentNode;
michael@13:             }
michael@13:             
michael@13:             if ( api.goto(target) ) {
michael@13:                 event.preventDefault();
michael@13:             }
michael@13:         }, false);
michael@13:         
michael@13:         // touch handler to detect taps on the left and right side of the screen
michael@13:         // based on awesome work of @hakimel: https://github.com/hakimel/reveal.js
michael@13:         document.addEventListener("touchstart", function ( event ) {
michael@13:             if (event.touches.length === 1) {
michael@13:                 var x = event.touches[0].clientX,
michael@13:                     width = window.innerWidth * 0.3,
michael@13:                     result = null;
michael@13:                     
michael@13:                 if ( x < width ) {
michael@13:                     result = api.prev();
michael@13:                 } else if ( x > window.innerWidth - width ) {
michael@13:                     result = api.next();
michael@13:                 }
michael@13:                 
michael@13:                 if (result) {
michael@13:                     event.preventDefault();
michael@13:                 }
michael@13:             }
michael@13:         }, false);
michael@13:         
michael@13:         // rescale presentation when window is resized
michael@13:         window.addEventListener("resize", throttle(function () {
michael@13:             // force going to active step again, to trigger rescaling
michael@13:             api.goto( document.querySelector(".active"), 500 );
michael@13:         }, 250), false);
michael@13:         
michael@13:     }, false);
michael@13:         
michael@13: })(document, window);
michael@13: 
michael@13: // THAT'S ALL FOLKS!
michael@13: //
michael@13: // Thanks for reading it all.
michael@13: // Or thanks for scrolling down and reading the last part.
michael@13: //
michael@13: // I've learnt a lot when building impress.js and I hope this code and comments
michael@13: // will help somebody learn at least some part of it.