1 files changed, 177 insertions, 39 deletions

diff --git a/js/reveal.js b/js/reveal.js
index 5c026db..56719cc 100644
--- a/js/reveal.js
+++ b/js/reveal.js
@@ -3,7 +3,7 @@
  * http://revealjs.com
  * MIT licensed
  *
- * Copyright (C) 2019 Hakim El Hattab, http://hakim.se
+ * Copyright (C) 2020 Hakim El Hattab, http://hakim.se
  */
 (function( root, factory ) {
 	if( typeof define === 'function' && define.amd ) {
@@ -270,6 +270,11 @@
 			// Number of slides away from the current that are visible
 			viewDistance: 3,
 
+			// Number of slides away from the current that are visible on mobile
+			// devices. It is advisable to set this to a lower number than
+			// viewDistance in order to save resources.
+			mobileViewDistance: 2,
+
 			// The display mode that will be used to show slides
 			display: 'block',
 
@@ -447,7 +452,8 @@
 	 */
 	function checkCapabilities() {
 
-		isMobileDevice = /(iphone|ipod|ipad|android)/gi.test( UA );
+		isMobileDevice = /(iphone|ipod|ipad|android)/gi.test( UA ) ||
+							( navigator.platform === 'MacIntel' && navigator.maxTouchPoints > 1 ); // iPadOS
 		isChrome = /chrome/i.test( UA ) && !/edge/i.test( UA );
 
 		var testElement = document.createElement( 'div' );
@@ -1217,6 +1223,8 @@
 		if( data.backgroundColor ) element.style.backgroundColor = data.backgroundColor;
 		if( data.backgroundTransition ) element.setAttribute( 'data-background-transition', data.backgroundTransition );
 
+		if( slide.hasAttribute( 'data-preload' ) ) element.setAttribute( 'data-preload', '' );
+
 		// Background image options are set on the content wrapper
 		if( data.backgroundSize ) contentElement.style.backgroundSize = data.backgroundSize;
 		if( data.backgroundRepeat ) contentElement.style.backgroundRepeat = data.backgroundRepeat;
@@ -1276,7 +1284,11 @@
 
 					// Check if the requested method can be found
 					if( data.method && typeof Reveal[data.method] === 'function' ) {
-						Reveal[data.method].apply( Reveal, data.args );
+						var result = Reveal[data.method].apply( Reveal, data.args );
+
+						// Dispatch a postMessage event with the returned value from
+						// our method invocation for getter functions
+						dispatchPostMessage( 'callback', { method: data.method, result: result } );
 					}
 				}
 			}, false );
@@ -1447,8 +1459,8 @@
 			keyboardShortcuts['↓  ,  J'] = 'Navigate down';
 		}
 
-		keyboardShortcuts['Home  ,  ⌘/CTRL ←'] = 'First slide';
-		keyboardShortcuts['End  ,  ⌘/CTRL →']  = 'Last slide';
+		keyboardShortcuts['Home  ,  Shift ←']        = 'First slide';
+		keyboardShortcuts['End  ,  Shift →']         = 'Last slide';
 		keyboardShortcuts['B  ,  .']                       = 'Pause';
 		keyboardShortcuts['F']                             = 'Fullscreen';
 		keyboardShortcuts['ESC, O']                        = 'Slide overview';
@@ -1981,8 +1993,25 @@
 
 		// If we're in an iframe, post each reveal.js event to the
 		// parent window. Used by the notes plugin
+		dispatchPostMessage( type );
+
+	}
+
+	/**
+	 * Dispatched a postMessage of the given type from our window.
+	 */
+	function dispatchPostMessage( type, data ) {
+
 		if( config.postMessageEvents && window.parent !== window.self ) {
-			window.parent.postMessage( JSON.stringify({ namespace: 'reveal', eventName: type, state: getState() }), '*' );
+			var message = {
+				namespace: 'reveal',
+				eventName: type,
+				state: getState()
+			};
+
+			extend( message, data );
+
+			window.parent.postMessage( JSON.stringify( message ), '*' );
 		}
 
 	}
@@ -2243,10 +2272,12 @@
 					transformSlides( { layout: '' } );
 				}
 				else {
-					// Prefer zoom for scaling up so that content remains crisp.
-					// Don't use zoom to scale down since that can lead to shifts
-					// in text layout/line breaks.
-					if( scale > 1 && features.zoom ) {
+					// Zoom Scaling
+					// Content remains crisp no matter how much we scale. Side
+					// effects are minor differences in text layout and iframe
+					// viewports changing size. A 200x200 iframe viewport in a
+					// 2x zoomed presentation ends up having a 400x400 viewport.
+					if( scale > 1 && features.zoom && window.devicePixelRatio < 2 ) {
 						dom.slides.style.zoom = scale;
 						dom.slides.style.left = '';
 						dom.slides.style.top = '';
@@ -2254,7 +2285,10 @@
 						dom.slides.style.right = '';
 						transformSlides( { layout: '' } );
 					}
-					// Apply scale transform as a fallback
+					// Transform Scaling
+					// Content layout remains the exact same when scaled up.
+					// Side effect is content becoming blurred, especially with
+					// high scale values on ldpi screens.
 					else {
 						dom.slides.style.zoom = '';
 						dom.slides.style.left = '50%';
@@ -3039,11 +3073,11 @@
 		syncBackground( slide );
 		syncFragments( slide );
 
+		loadSlide( slide );
+
 		updateBackground();
 		updateNotes();
 
-		loadSlide( slide );
-
 	}
 
 	/**
@@ -3255,9 +3289,10 @@
 			// be visible
 			var viewDistance = isOverview() ? 10 : config.viewDistance;
 
-			// Limit view distance on weaker devices
+			// Shorten the view distance on devices that typically have
+			// less resources
 			if( isMobileDevice ) {
-				viewDistance = isOverview() ? 6 : 2;
+				viewDistance = isOverview() ? 6 : config.mobileViewDistance;
 			}
 
 			// All slides need to be visible when exporting to PDF
@@ -3309,7 +3344,7 @@
 			}
 
 			// Flag if there are ANY vertical slides, anywhere in the deck
-			if( dom.wrapper.querySelectorAll( '.slides>section>section' ).length ) {
+			if( hasVerticalSlides() ) {
 				dom.wrapper.classList.add( 'has-vertical-slides' );
 			}
 			else {
@@ -3317,7 +3352,7 @@
 			}
 
 			// Flag if there are ANY horizontal slides, anywhere in the deck
-			if( dom.wrapper.querySelectorAll( '.slides>section' ).length > 1 ) {
+			if( hasHorizontalSlides() ) {
 				dom.wrapper.classList.add( 'has-horizontal-slides' );
 			}
 			else {
@@ -3599,7 +3634,7 @@
 		// Stop content inside of previous backgrounds
 		if( previousBackground ) {
 
-			stopEmbeddedContent( previousBackground );
+			stopEmbeddedContent( previousBackground, { unloadIframes: !shouldPreload( previousBackground ) } );
 
 		}
 
@@ -3778,6 +3813,7 @@
 			background.style.display = 'block';
 
 			var backgroundContent = slide.slideBackgroundContentElement;
+			var backgroundIframe = slide.getAttribute( 'data-background-iframe' );
 
 			// If the background contains media, load it
 			if( background.hasAttribute( 'data-loaded' ) === false ) {
@@ -3786,8 +3822,7 @@
 				var backgroundImage = slide.getAttribute( 'data-background-image' ),
 					backgroundVideo = slide.getAttribute( 'data-background-video' ),
 					backgroundVideoLoop = slide.hasAttribute( 'data-background-video-loop' ),
-					backgroundVideoMuted = slide.hasAttribute( 'data-background-video-muted' ),
-					backgroundIframe = slide.getAttribute( 'data-background-iframe' );
+					backgroundVideoMuted = slide.hasAttribute( 'data-background-video-muted' );
 
 				// Images
 				if( backgroundImage ) {
@@ -3827,15 +3862,9 @@
 					iframe.setAttribute( 'allowfullscreen', '' );
 					iframe.setAttribute( 'mozallowfullscreen', '' );
 					iframe.setAttribute( 'webkitallowfullscreen', '' );
+					iframe.setAttribute( 'allow', 'autoplay' );
 
-					// Only load autoplaying content when the slide is shown to
-					// avoid having it play in the background
-					if( /autoplay=(1|true|yes)/gi.test( backgroundIframe ) ) {
-						iframe.setAttribute( 'data-src', backgroundIframe );
-					}
-					else {
-						iframe.setAttribute( 'src', backgroundIframe );
-					}
+					iframe.setAttribute( 'data-src', backgroundIframe );
 
 					iframe.style.width  = '100%';
 					iframe.style.height = '100%';
@@ -3846,6 +3875,19 @@
 				}
 			}
 
+			// Start loading preloadable iframes
+			var backgroundIframeElement = backgroundContent.querySelector( 'iframe[data-src]' );
+			if( backgroundIframeElement ) {
+
+				// Check if this iframe is eligible to be preloaded
+				if( shouldPreload( background ) && !/autoplay=(1|true|yes)/gi.test( backgroundIframe ) ) {
+					if( backgroundIframeElement.getAttribute( 'src' ) !== backgroundIframe ) {
+						backgroundIframeElement.setAttribute( 'src', backgroundIframe );
+					}
+				}
+
+			}
+
 		}
 
 	}
@@ -3865,6 +3907,11 @@
 		var background = getSlideBackground( slide );
 		if( background ) {
 			background.style.display = 'none';
+
+			// Unload any background iframes
+			toArray( background.querySelectorAll( 'iframe[src]' ) ).forEach( function( element ) {
+				element.removeAttribute( 'src' );
+			} );
 		}
 
 		// Reset lazy-loaded media elements with src attributes
@@ -4429,7 +4476,44 @@
 	 */
 	function getSlides() {
 
-		return toArray( dom.wrapper.querySelectorAll( SLIDES_SELECTOR + ':not(.stack)' ));
+		return toArray( dom.wrapper.querySelectorAll( SLIDES_SELECTOR + ':not(.stack)' ) );
+
+	}
+
+	/**
+	 * Returns a list of all horizontal slides in the deck. Each
+	 * vertical stack is included as one horizontal slide in the
+	 * resulting array.
+	 */
+	function getHorizontalSlides() {
+
+		return toArray( dom.wrapper.querySelectorAll( HORIZONTAL_SLIDES_SELECTOR ) );
+
+	}
+
+	/**
+	 * Returns all vertical slides that exist within this deck.
+	 */
+	function getVerticalSlides() {
+
+		return toArray( dom.wrapper.querySelectorAll( '.slides>section>section' ) );
+
+	}
+
+	/**
+	 * Returns true if there are at least two horizontal slides.
+	 */
+	function hasHorizontalSlides() {
+
+		return getHorizontalSlides().length > 1;
+	}
+
+	/**
+	 * Returns true if there are at least two vertical slides.
+	 */
+	function hasVerticalSlides() {
+
+		return getVerticalSlides().length > 1;
 
 	}
 
@@ -4667,6 +4751,8 @@
 
 			if( fragments.length ) {
 
+				var maxIndex = 0;
+
 				if( typeof index !== 'number' ) {
 					var currentFragment = sortFragments( currentSlide.querySelectorAll( '.fragment.visible' ) ).pop();
 					if( currentFragment ) {
@@ -4680,6 +4766,8 @@
 						i = parseInt( el.getAttribute( 'data-fragment-index' ), 10 );
 					}
 
+					maxIndex = Math.max( maxIndex, i );
+
 					// Visible fragments
 					if( i <= index ) {
 						if( !el.classList.contains( 'visible' ) ) changedFragments.shown.push( el );
@@ -4703,6 +4791,13 @@
 
 				} );
 
+				// Write the current fragment index to the slide <section>.
+				// This can be used by end users to apply styles based on
+				// the current fragment index.
+				index = typeof index === 'number' ? index : -1;
+				index = Math.max( Math.min( index, maxIndex ), -1 );
+				currentSlide.setAttribute( 'data-fragment', index );
+
 			}
 
 		}
@@ -5116,8 +5211,8 @@
 
 		// Whitelist specific modified + keycode combinations
 		var prevSlideShortcut = event.shiftKey && event.keyCode === 32;
-		var firstSlideShortcut = ( event.metaKey || event.ctrlKey ) && keyCode === 37;
-		var lastSlideShortcut = ( event.metaKey || event.ctrlKey ) && keyCode === 39;
+		var firstSlideShortcut = event.shiftKey && keyCode === 37;
+		var lastSlideShortcut = event.shiftKey && keyCode === 39;
 
 		// Prevent all other events when a modifier is pressed
 		var unusedModifier = 	!prevSlideShortcut && !firstSlideShortcut && !lastSlideShortcut &&
@@ -5144,6 +5239,10 @@
 			return false;
 		}
 
+		// Use linear navigation if we're configured to OR if
+		// the presentation is one-dimensional
+		var useLinearMode = config.navigationMode === 'linear' || !hasHorizontalSlides() || !hasVerticalSlides();
+
 		var triggered = false;
 
 		// 1. User defined key bindings
@@ -5216,7 +5315,7 @@
 				if( firstSlideShortcut ) {
 					slide( 0 );
 				}
-				else if( !isOverview() && config.navigationMode === 'linear' ) {
+				else if( !isOverview() && useLinearMode ) {
 					navigatePrev();
 				}
 				else {
@@ -5228,7 +5327,7 @@
 				if( lastSlideShortcut ) {
 					slide( Number.MAX_VALUE );
 				}
-				else if( !isOverview() && config.navigationMode === 'linear' ) {
+				else if( !isOverview() && useLinearMode ) {
 					navigateNext();
 				}
 				else {
@@ -5237,7 +5336,7 @@
 			}
 			// K, UP
 			else if( keyCode === 75 || keyCode === 38 ) {
-				if( !isOverview() && config.navigationMode === 'linear' ) {
+				if( !isOverview() && useLinearMode ) {
 					navigatePrev();
 				}
 				else {
@@ -5246,7 +5345,7 @@
 			}
 			// J, DOWN
 			else if( keyCode === 74 || keyCode === 40 ) {
-				if( !isOverview() && config.navigationMode === 'linear' ) {
+				if( !isOverview() && useLinearMode ) {
 					navigateNext();
 				}
 				else {
@@ -5356,19 +5455,49 @@
 
 				if( deltaX > touch.threshold && Math.abs( deltaX ) > Math.abs( deltaY ) ) {
 					touch.captured = true;
-					navigateLeft();
+					if( config.navigationMode === 'linear' ) {
+						if( config.rtl ) {
+							navigateNext();
+						}
+						else {
+							navigatePrev();
+						}
+					}
+					else {
+						navigateLeft();
+					}
 				}
 				else if( deltaX < -touch.threshold && Math.abs( deltaX ) > Math.abs( deltaY ) ) {
 					touch.captured = true;
-					navigateRight();
+					if( config.navigationMode === 'linear' ) {
+						if( config.rtl ) {
+							navigatePrev();
+						}
+						else {
+							navigateNext();
+						}
+					}
+					else {
+						navigateRight();
+					}
 				}
 				else if( deltaY > touch.threshold ) {
 					touch.captured = true;
-					navigateUp();
+					if( config.navigationMode === 'linear' ) {
+						navigatePrev();
+					}
+					else {
+						navigateUp();
+					}
 				}
 				else if( deltaY < -touch.threshold ) {
 					touch.captured = true;
-					navigateDown();
+					if( config.navigationMode === 'linear' ) {
+						navigateNext();
+					}
+					else {
+						navigateDown();
+					}
 				}
 
 				// If we're embedded, only block touch events if they have
@@ -5905,6 +6034,15 @@
 		// Returns the speaker notes string for a slide, or null
 		getSlideNotes: getSlideNotes,
 
+		// Returns an array with all horizontal/vertical slides in the deck
+		getHorizontalSlides: getHorizontalSlides,
+		getVerticalSlides: getVerticalSlides,
+
+		// Checks if the presentation contains two or more
+		// horizontal/vertical slides
+		hasHorizontalSlides: hasHorizontalSlides,
+		hasVerticalSlides: hasVerticalSlides,
+
 		// Returns the previous slide element, may be null
 		getPreviousSlide: function() {
 			return previousSlide;