finishing touches on reader mode progress bar

css/reveal.scss

@@ -2011,6 +2011,13 @@ $notesWidthPercent: 25%;
 	position: sticky;
 	top: 50%;
 	z-index: 20;
+	opacity: 0;
+	transition: all 0.3s ease;
+
+	&.visible,
+	&:hover {
+		opacity: 1;
+	}
 
 	.reader-progress-inner {
 		position: absolute;
@@ -2021,6 +2028,18 @@ $notesWidthPercent: 25%;
 		transform: translateY(-50%);
 		border-radius: 8px;
 		z-index: 10;
+
+		// Hit area
+		&:after {
+			content: '';
+			position: absolute;
+			width: 200%;
+			height: 100%;
+			top: 0;
+			left: -50%;
+			background: rgba( 0, 0, 0, 0 );
+			z-index: -1;
+		}
 	}
 
 	.reader-progress-playhead {

js/config.js

@@ -276,9 +276,15 @@ export default {
 	// Only applies to presentations in reader mode.
 	readerScrollSnap: 'proximity',
 
+	// Enables and configure the reader mode scroll bar.
+	// - 'auto':    Show the scrollbar while scrolling, hide while idle
+	// - true:      Always show the scrollbar
+	// - false:     Never show the scrollbar
+	readerScrollBar: 'auto',
+
 	// Responsively activate the reader mode when we reach the specified
 	// width (in pixels)
-	readerActivationWidth: 800,
+	readerActivationWidth: null,
 
 	// The maximum number of pages a single slide can expand onto when printing
 	// to PDF, unlimited by default

js/controllers/reader.js

@@ -1,6 +1,8 @@
 import { HORIZONTAL_SLIDES_SELECTOR, SLIDES_SELECTOR } from '../utils/constants.js'
 import { queryAll, createStyleSheet } from '../utils/util.js'
 
+const HIDE_SCROLLBAR_TIMEOUT = 500;
+
 /**
  * The reader mode lets you read a reveal.js presentation
  * as a linear scrollable page.
@@ -116,52 +118,6 @@ export default class Reader {
 
 	}
 
-	createProgressBar() {
-
-		this.progressBar = document.createElement( 'div' );
-		this.progressBar.className = 'reader-progress';
-
-		this.progressBarInner = document.createElement( 'div' );
-		this.progressBarInner.className = 'reader-progress-inner';
-		this.progressBar.appendChild( this.progressBarInner );
-
-		this.progressBarPlayhead = document.createElement( 'div' );
-		this.progressBarPlayhead.className = 'reader-progress-playhead';
-		this.progressBarInner.appendChild( this.progressBarPlayhead );
-
-		this.viewportElement.insertBefore( this.progressBar, this.viewportElement.firstChild );
-
-		const handleMouseDown = ( event ) => {
-
-			event.preventDefault();
-
-			document.addEventListener( 'mousemove', handleDocumentMouseMove );
-			document.addEventListener( 'mouseup', handleDocumentMouseUp );
-
-			handleDocumentMouseMove( event );
-
-		};
-
-		const handleDocumentMouseMove	= ( event ) => {
-
-			let progress = Math.max( Math.min( ( event.clientY - this.progressBarInner.getBoundingClientRect().top ) / this.progressBarHeight, 1 ), 0 );
-			progress = Math.max( Math.min( progress, 1 ), 0 );
-
-			this.viewportElement.scrollTop = progress * ( this.viewportElement.scrollHeight - this.viewportElement.offsetHeight );
-
-		};
-
-		const handleDocumentMouseUp = ( event ) => {
-
-			document.removeEventListener( 'mousemove', handleDocumentMouseMove );
-			document.removeEventListener( 'mouseup', handleDocumentMouseUp );
-
-		};
-
-		this.progressBarInner.addEventListener( 'mousedown', handleMouseDown );
-
-	}
-
 	/**
 	 * Deactivates the reader mode and restores the standard slide-based
 	 * presentation.
@@ -177,7 +133,7 @@ export default class Reader {
 		this.viewportElement.removeEventListener( 'scroll', this.onScroll );
 		this.viewportElement.classList.remove( 'reveal-reader' );
 
-		this.progressBar.remove();
+		this.removeProgressBar();
 
 		this.Reveal.getSlidesElement().innerHTML = this.slideHTMLBeforeActivation;
 		this.Reveal.sync();
@@ -324,7 +280,76 @@ export default class Reader {
 			return page;
 		} );
 
+		if( config.readerScrollBar ) {
+			this.createProgressBar();
 			this.createProgressBarSlides();
+		}
+		else {
+			this.removeProgressBar();
+		}
+
+	}
+
+	createProgressBar() {
+
+		if( this.progressBar ) return;
+
+		this.progressBar = document.createElement( 'div' );
+		this.progressBar.className = 'reader-progress';
+
+		this.progressBarInner = document.createElement( 'div' );
+		this.progressBarInner.className = 'reader-progress-inner';
+		this.progressBar.appendChild( this.progressBarInner );
+
+		this.progressBarPlayhead = document.createElement( 'div' );
+		this.progressBarPlayhead.className = 'reader-progress-playhead';
+		this.progressBarInner.appendChild( this.progressBarPlayhead );
+
+		this.viewportElement.insertBefore( this.progressBar, this.viewportElement.firstChild );
+
+		const handleMouseDown = ( event ) => {
+
+			event.preventDefault();
+
+			this.draggingProgressBar = true;
+
+			document.addEventListener( 'mousemove', handleDocumentMouseMove );
+			document.addEventListener( 'mouseup', handleDocumentMouseUp );
+
+			handleDocumentMouseMove( event );
+
+		};
+
+		const handleDocumentMouseMove	= ( event ) => {
+
+			let progress = ( event.clientY - this.progressBarInner.getBoundingClientRect().top ) / this.progressBarHeight;
+
+			progress = Math.max( Math.min( progress, 1 ), 0 );
+
+			this.viewportElement.scrollTop = progress * ( this.viewportElement.scrollHeight - this.viewportElement.offsetHeight );
+
+		};
+
+		const handleDocumentMouseUp = ( event ) => {
+
+			this.draggingProgressBar = false;
+			this.showProgressBar();
+
+			document.removeEventListener( 'mousemove', handleDocumentMouseMove );
+			document.removeEventListener( 'mouseup', handleDocumentMouseUp );
+
+		};
+
+		this.progressBarInner.addEventListener( 'mousedown', handleMouseDown );
+
+	}
+
+	removeProgressBar() {
+
+		if( this.progressBar ) {
+			this.progressBar.remove();
+			this.progressBar = null;
+		}
 
 	}
 
@@ -377,12 +402,34 @@ export default class Reader {
 
 	moveProgressBarTo( progress ) {
 
+		if( this.progressBar ) {
+
 			this.progressBarPlayhead.style.transform = `translateY(${progress * this.progressBarScrollableHeight}px)`;
 
 			this.pages.forEach( ( page ) => {
 				page.progressBarSlide.classList.toggle( 'active', !!page.active );
 			} );
 
+			this.showProgressBar();
+
+		}
+
+	}
+
+	showProgressBar() {
+
+		this.progressBar.classList.add( 'visible' );
+
+		clearTimeout( this.hideProgressBarTimeout );
+
+		if( this.Reveal.getConfig().readerScrollBar === 'auto' && !this.draggingProgressBar ) {
+
+			this.hideProgressBarTimeout = setTimeout( () => {
+				this.progressBar.classList.remove( 'visible' );
+			}, HIDE_SCROLLBAR_TIMEOUT );
+
+		}
+
 	}
 
 	scrollToSlide( slideElement ) {