refactoring and optimization of overview mode

css/reveal.css

@@ -639,9 +639,10 @@ body {
   opacity: 1 !important;
   visibility: visible !important;
   cursor: pointer;
-  background: rgba(0, 0, 0, 0.1);
   -moz-box-sizing: border-box;
-       box-sizing: border-box; }
+       box-sizing: border-box;
+  outline: 10px solid rgba(150, 150, 150, 0.1);
+  outline-offset: 10px; }
 
 .reveal.overview .slides section, .reveal.overview-deactivating .slides section {
   -webkit-transition: none !important;
@@ -657,16 +658,14 @@ body {
   opacity: 1;
   cursor: pointer; }
 
-.reveal.overview .slides section:hover {
+.reveal.overview .slides section:hover, .reveal.overview .slides section.present {
-  background: rgba(0, 0, 0, 0.3); }
+  outline: 10px solid rgba(150, 150, 150, 0.5); }
-
-.reveal.overview .slides section.present {
-  background: rgba(0, 0, 0, 0.3); }
 
 .reveal.overview .slides > section.stack {
   padding: 0;
   top: 0 !important;
   background: none;
+  outline: none;
   overflow: visible; }
 
 .reveal.overview .backgrounds {
@@ -681,6 +680,10 @@ body {
   -webkit-transition: none !important;
           transition: none !important; }
 
+.reveal.overview-animated .slides {
+  -webkit-transition: -webkit-transform 0.4s ease;
+          transition: transform 0.4s ease; }
+
 /*********************************************
  * PAUSED MODE
  *********************************************/

css/reveal.scss

@@ -753,8 +753,9 @@ body {
 	opacity: 1 !important;
 	visibility: visible !important;
 	cursor: pointer;
-	background: rgba(0,0,0,0.1);
 	box-sizing: border-box;
+	outline: 10px solid rgba(150,150,150,0.1);
+	outline-offset: 10px;
 }
 .reveal.overview .slides section,
 .reveal.overview-deactivating .slides section {
@@ -771,16 +772,15 @@ body {
 	opacity: 1;
 	cursor: pointer;
 }
-	.reveal.overview .slides section:hover {
+	.reveal.overview .slides section:hover,
-		background: rgba(0,0,0,0.3);
-	}
 	.reveal.overview .slides section.present {
-		background: rgba(0,0,0,0.3);
+		outline: 10px solid rgba(150,150,150,0.5);
 	}
 .reveal.overview .slides>section.stack {
 	padding: 0;
 	top: 0 !important;
 	background: none;
+	outline: none;
 	overflow: visible;
 }
 
@@ -796,6 +796,10 @@ body {
 	transition: none !important;
 }
 
+.reveal.overview-animated .slides {
+	transition: transform 0.4s ease;
+}
+
 
 /*********************************************
  * PAUSED MODE

js/reveal.js

@@ -147,6 +147,9 @@
 		// Flags if reveal.js is loaded (has dispatched the 'ready' event)
 		loaded = false,
 
+		// Flags if the overview mode is currently active
+		overview = false,
+
 		// The horizontal and vertical index of the currently active slide
 		indexh,
 		indexv,
@@ -165,8 +168,9 @@
 		// The current scale of the presentation (see width/height config)
 		scale = 1,
 
-		// The current z position of the presentation container
+		// The transform that is currently applied to the slides container
-		z = 0,
+		slidesTransform = '',
+		layoutTransform = '',
 
 		// Cached references to DOM elements
 		dom = {},
@@ -1058,6 +1062,12 @@
 
 	}
 
+	function transformSlides() {
+
+		transformElement( dom.slides, layoutTransform ? layoutTransform + ' ' + slidesTransform : slidesTransform );
+
+	}
+
 	/**
 	 * Injects the given CSS styles into the DOM.
 	 */
@@ -1446,7 +1456,6 @@
 			var size = getComputedSlideSize();
 
 			var slidePadding = 20; // TODO Dig this out of DOM
-			var zTransform = z !== 0 ? 'translateZ(-'+ z +'px)' : '';
 
 			// Layout the contents of the slides
 			layoutSlideContents( config.width, config.height, slidePadding );
@@ -1468,13 +1477,12 @@
 				dom.slides.style.top = '';
 				dom.slides.style.bottom = '';
 				dom.slides.style.right = '';
-				transformElement( dom.slides, zTransform );
+				layoutTransform = '';
 			}
 			else {
 				// Prefer zooming in desktop Chrome so that content remains crisp
 				if( !isMobileDevice && /chrome/i.test( navigator.userAgent ) && typeof dom.slides.style.zoom !== 'undefined' ) {
 					dom.slides.style.zoom = scale;
-					transformElement( dom.slides, zTransform );
 				}
 				// Apply scale transform as a fallback
 				else {
@@ -1482,10 +1490,12 @@
 					dom.slides.style.top = '50%';
 					dom.slides.style.bottom = 'auto';
 					dom.slides.style.right = 'auto';
-					transformElement( dom.slides, 'translate(-50%, -50%) scale('+ scale +') ' + zTransform );
+					layoutTransform = 'translate(-50%, -50%) scale('+ scale +')';
 				}
 			}
 
+			transformSlides();
+
 			// Select all slides, vertical and horizontal
 			var slides = toArray( dom.wrapper.querySelectorAll( SLIDES_SELECTOR ) );
 
@@ -1633,20 +1643,23 @@
 	function activateOverview() {
 
 		// Only proceed if enabled in config
-		if( config.overview ) {
+		if( config.overview && !isOverview() ) {
+
+			overview = true;
+
+			dom.wrapper.classList.add( 'overview' );
+			dom.wrapper.classList.remove( 'overview-deactivating' );
+
+			setTimeout( function() {
+				dom.wrapper.classList.add( 'overview-animated' );
+			}, 1 );
 
 			// Don't auto-slide while in overview mode
 			cancelAutoSlide();
 
-			var wasActive = dom.wrapper.classList.contains( 'overview' );
+			var margin = 70;
-
+			var slideWidth = config.width + margin,
-			// Set the depth of the presentation. This determinse how far we
+				slideHeight = config.height + margin;
-			// zoom out and varies based on display size. It gets applied at
-			// the layout step.
-			z = window.innerWidth < 400 ? 1000 : 2500;
-
-			dom.wrapper.classList.add( 'overview' );
-			dom.wrapper.classList.remove( 'overview-deactivating' );
 
 			// Move the backgrounds element into the slide container to
 			// that the same scaling is applied
@@ -1658,9 +1671,9 @@
 			for( var i = 0, len1 = horizontalSlides.length; i < len1; i++ ) {
 				var hslide = horizontalSlides[i],
 					hbackground = horizontalBackgrounds[i],
-					hoffset = config.rtl ? -105 : 105;
+					hoffset = config.rtl ? -slideWidth : slideWidth;
 
-				var htransform = 'translate(' + ( ( i - indexh ) * hoffset ) + '%, 0%)';
+				var htransform = 'translateX(' + ( i * hoffset ) + 'px)';
 
 				hslide.setAttribute( 'data-index-h', i );
 
@@ -1679,7 +1692,7 @@
 						var vslide = verticalSlides[j],
 							vbackground = verticalBackgrounds[j];
 
-						var vtransform = 'translate(0%, ' + ( ( j - verticalIndex ) * 105 ) + '%)';
+						var vtransform = 'translateY(' + ( j * slideHeight ) + 'px)';
 
 						vslide.setAttribute( 'data-index-h', i );
 						vslide.setAttribute( 'data-index-v', j );
@@ -1702,20 +1715,36 @@
 			}
 
 			updateSlidesVisibility();
+			updateOverview();
 
 			layout();
 
-			if( !wasActive ) {
 			// Notify observers of the overview showing
 			dispatchEvent( 'overviewshown', {
 				'indexh': indexh,
 				'indexv': indexv,
 				'currentSlide': currentSlide
 			} );
+
 		}
 
 	}
 
+	function updateOverview() {
+
+		var z = window.innerWidth < 400 ? 1000 : 2500;
+		var margin = 70;
+		var slideWidth = config.width + margin,
+			slideHeight = config.height + margin;
+
+		slidesTransform = [
+			'translateX('+ ( -indexh * slideWidth ) +'px)',
+			'translateY('+ ( -indexv * slideHeight ) +'px)',
+			'translateZ('+ ( -z ) +'px)'
+		].join( ' ' );
+
+		transformSlides();
+
 	}
 
 	/**
@@ -1727,11 +1756,17 @@
 		// Only proceed if enabled in config
 		if( config.overview ) {
 
+			slidesTransform = '';
+
+			overview = false;
+
 			dom.wrapper.classList.remove( 'overview' );
 
 			// Move the background element back out
 			dom.wrapper.appendChild( dom.background );
 
+			dom.wrapper.classList.remove( 'overview-animated' );
+
 			// Temporarily add a class so that transitions can do different things
 			// depending on whether they are exiting/entering overview, or just
 			// moving from slide to slide
@@ -1755,6 +1790,8 @@
 
 			slide( indexh, indexv );
 
+			layout();
+
 			cueAutoSlide();
 
 			// Notify observers of the overview hiding
@@ -1793,7 +1830,7 @@
 	 */
 	function isOverview() {
 
-		return dom.wrapper.classList.contains( 'overview' );
+		return overview;
 
 	}
 
@@ -1995,7 +2032,7 @@
 
 		// If the overview is active, re-activate it to update positions
 		if( isOverview() ) {
-			activateOverview();
+			updateOverview();
 		}
 
 		// Find the current horizontal slide and any possible vertical slides
@@ -2289,11 +2326,11 @@
 
 			// The number of steps away from the present slide that will
 			// be visible
-			var viewDistance = isOverview() ? 10 : config.viewDistance;
+			var viewDistance = isOverview() ? 7 : config.viewDistance;
 
 			// Limit view distance on weaker devices
 			if( isMobileDevice ) {
-				viewDistance = isOverview() ? 6 : 2;
+				viewDistance = isOverview() ? 7 : 2;
 			}
 
 			// Limit view distance on weaker devices