reveal.js

	 * Cues a new automated slide if enabled in the config.
	 */
	function cueAutoSlide() {
		clearTimeout( autoSlideTimeout );

		// Cue the next auto-slide if enabled
		if( autoSlide ) {
			autoSlideTimeout = setTimeout( navigateNext, autoSlide );
		}
	}
	
	function navigateLeft() {
		// Prioritize hiding fragments
		if( isOverviewActive() || previousFragment() === false ) {
			slide( indexh - 1, 0 );
		}
	}

	function navigateRight() {
		// Prioritize revealing fragments
		if( isOverviewActive() || nextFragment() === false ) {
			slide( indexh + 1, 0 );
		}
	}

	function navigateUp() {
		// Prioritize hiding fragments
		if( isOverviewActive() || previousFragment() === false ) {
			slide( indexh, indexv - 1 );
		}
	}

	function navigateDown() {
		// Prioritize revealing fragments
		if( isOverviewActive() || nextFragment() === false ) {
			slide( indexh, indexv + 1 );
		}
	}

	/**
	 * Navigates backwards, prioritized in the following order:
	 * 1) Previous fragment
	 * 2) Previous vertical slide
	 * 3) Previous horizontal slide
	 */
	function navigatePrev() {
		// Prioritize revealing fragments
		if( previousFragment() === false ) {
			if( availableRoutes().up ) {
				navigateUp();
			}
			else {
				// Fetch the previous horizontal slide, if there is one
				var previousSlide = document.querySelector( '.reveal .slides>section.past:nth-child(' + indexh + ')' );

				if( previousSlide ) {
					indexv = ( previousSlide.querySelectorAll('section').length + 1 ) || 0;
					indexh --;
					slide();
				}
			}
		}
	}

	/**
	 * Same as #navigatePrev() but navigates forwards.
	 */
	function navigateNext() {
		// Prioritize revealing fragments
		if( nextFragment() === false ) {
			availableRoutes().down ? navigateDown() : navigateRight();
		}

		// If auto-sliding is enabled we need to cue up 
		// another timeout
		cueAutoSlide();
	}


	// --------------------------------------------------------------------//
	// ----------------------------- EVENTS -------------------------------//
	// --------------------------------------------------------------------//


	/**
	 * Handler for the document level 'keydown' event.
	 * 
	 * @param {Object} event
	 */
	function onDocumentKeyDown( event ) {
		// Disregard the event if the target is editable or a 
		// modifier is present
		if ( document.querySelector( ':focus' ) !== null || event.shiftKey || event.altKey || event.ctrlKey || event.metaKey ) return;

		var triggered = true;

		switch( event.keyCode ) {
			// p, page up
			case 80: case 33: navigatePrev(); break; 
			// n, page down
			case 78: case 34: navigateNext(); break;
			// h, left
			case 72: case 37: navigateLeft(); break;
			// l, right
			case 76: case 39: navigateRight(); break;
			// k, up
			case 75: case 38: navigateUp(); break;
			// j, down
			case 74: case 40: navigateDown(); break;
			// home
			case 36: slide( 0 ); break;
			// end
			case 35: slide( Number.MAX_VALUE ); break;
			// space
			case 32: isOverviewActive() ? deactivateOverview() : navigateNext(); break;
			// return
			case 13: isOverviewActive() ? deactivateOverview() : triggered = false; break;
			// b, period
			case 66: case 190: togglePause(); break;
			// f
			case 70: enterFullscreen(); break;
			default:
				triggered = false;
		}

		// If the input resulted in a triggered action we should prevent 
		// the browsers default behavior
		if( triggered ) {
			event.preventDefault();
		}
		else if ( event.keyCode === 27 && supports3DTransforms ) {
			toggleOverview();
	
			event.preventDefault();
		}

		// If auto-sliding is enabled we need to cue up 
		// another timeout
		cueAutoSlide();

	}

	/**
	 * Handler for the document level 'touchstart' event,
	 * enables support for swipe and pinch gestures.
	 */
	function onDocumentTouchStart( event ) {
		touch.startX = event.touches[0].clientX;
		touch.startY = event.touches[0].clientY;
		touch.startCount = event.touches.length;

		// If there's two touches we need to memorize the distance 
		// between those two points to detect pinching
		if( event.touches.length === 2 && config.overview ) {
			touch.startSpan = distanceBetween( {
				x: event.touches[1].clientX,
				y: event.touches[1].clientY
			}, {
				x: touch.startX,
				y: touch.startY
			} );
		}
	}
	
	/**
	 * Handler for the document level 'touchmove' event.
	 */
	function onDocumentTouchMove( event ) {
		// Each touch should only trigger one action
		if( !touch.handled ) {
			var currentX = event.touches[0].clientX;
			var currentY = event.touches[0].clientY;

			// If the touch started off with two points and still has 
			// two active touches; test for the pinch gesture
			if( event.touches.length === 2 && touch.startCount === 2 && config.overview ) {

				// The current distance in pixels between the two touch points
				var currentSpan = distanceBetween( {
					x: event.touches[1].clientX,
					y: event.touches[1].clientY
				}, {
					x: touch.startX,
					y: touch.startY
				} );

				// If the span is larger than the desire amount we've got 
				// ourselves a pinch
				if( Math.abs( touch.startSpan - currentSpan ) > touch.threshold ) {
					touch.handled = true;

					if( currentSpan < touch.startSpan ) {
						activateOverview();
					}
					else {
						deactivateOverview();
					}
				}

				event.preventDefault();

			}
			// There was only one touch point, look for a swipe
			else if( event.touches.length === 1 && touch.startCount !== 2 ) {

				var deltaX = currentX - touch.startX,
					deltaY = currentY - touch.startY;

				if( deltaX > touch.threshold && Math.abs( deltaX ) > Math.abs( deltaY ) ) {
					touch.handled = true;
					navigateLeft();
				} 
				else if( deltaX < -touch.threshold && Math.abs( deltaX ) > Math.abs( deltaY ) ) {
					touch.handled = true;
					navigateRight();
				} 
				else if( deltaY > touch.threshold ) {
					touch.handled = true;
					navigateUp();
				} 
				else if( deltaY < -touch.threshold ) {
					touch.handled = true;
					navigateDown();
				}

				event.preventDefault();

			}
		}
		// There's a bug with swiping on some Android devices unless 
		// the default action is always prevented
		else if( navigator.userAgent.match( /android/gi ) ) {
			event.preventDefault();
		}
	}

	/**
	 * Handler for the document level 'touchend' event.
	 */
	function onDocumentTouchEnd( event ) {
		touch.handled = false;
	}

	/**
	 * Handles mouse wheel scrolling, throttled to avoid skipping 
	 * multiple slides.
	 */
	function onDocumentMouseScroll( event ){
		clearTimeout( mouseWheelTimeout );

		mouseWheelTimeout = setTimeout( function() {
			var delta = event.detail || -event.wheelDelta;
			if( delta > 0 ) {
				navigateNext();
			}
			else {
				navigatePrev();
			}
		}, 100 );
	}

	/**
	 * Clicking on the progress bar results in a navigation to the 
	 * closest approximate horizontal slide using this equation:
	 *
	 * ( clickX / presentationWidth ) * numberOfSlides
	 */
	function onProgressClick( event ) {
		var slidesTotal = Array.prototype.slice.call( document.querySelectorAll( HORIZONTAL_SLIDES_SELECTOR ) ).length;
		var slideIndex = Math.floor( ( event.clientX / dom.wrapper.offsetWidth ) * slidesTotal );

		slide( slideIndex );
	}
	
	/**
	 * Handler for the window level 'hashchange' event.
	 * 
	 * @param {Object} event
	 */
	function onWindowHashChange( event ) {
		readURL();
	}

	/**
	 * Invoked when a slide is and we're in the overview.
	 */
	function onOverviewSlideClicked( event ) {
		// TODO There's a bug here where the event listeners are not 
		// removed after deactivating the overview.
		if( isOverviewActive() ) {
			event.preventDefault();

			deactivateOverview();

			indexh = this.getAttribute( 'data-index-h' );
			indexv = this.getAttribute( 'data-index-v' );

			slide();
		}
	}

	
	// --------------------------------------------------------------------//
	// ------------------------------- API --------------------------------//
	// --------------------------------------------------------------------//


	return {
		initialize: initialize,
		
		// Navigation methods
		slide: slide,
		left: navigateLeft,
		right: navigateRight,
		up: navigateUp,
		down: navigateDown,
		prev: navigatePrev,
		next: navigateNext,

		// Deprecated aliases
		navigateTo: slide,
		navigateLeft: navigateLeft,
		navigateRight: navigateRight,
		navigateUp: navigateUp,
		navigateDown: navigateDown,
		navigatePrev: navigatePrev,
		navigateNext: navigateNext,

		// Toggles the overview mode on/off
		toggleOverview: toggleOverview,

		// Adds or removes all internal event listeners (such as keyboard)
		addEventListeners: addEventListeners,
		removeEventListeners: removeEventListeners,

		// Returns the indices of the current, or specified, slide
		getIndices: getIndices,

		// Returns the previous slide element, may be null
		getPreviousSlide: function() {
			return previousSlide;
		},

		// Returns the current slide element
		getCurrentSlide: function() {
			return currentSlide;
		},

		// Helper method, retrieves query string as a key/value hash
		getQueryHash: function() {
			var query = {};

			location.search.replace( /[A-Z0-9]+?=(\w*)/gi, function(a) {
				query[ a.split( '=' ).shift() ] = a.split( '=' ).pop();
			} );

			return query;
		},

		// Forward event binding to the reveal DOM element
		addEventListener: function( type, listener, useCapture ) {
			if( 'addEventListener' in window ) {
				( dom.wrapper || document.querySelector( '.reveal' ) ).addEventListener( type, listener, useCapture );
			}
		},
		removeEventListener: function( type, listener, useCapture ) {
			if( 'addEventListener' in window ) {
				( dom.wrapper || document.querySelector( '.reveal' ) ).removeEventListener( type, listener, useCapture );
			}
		}
	};
	
})();