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Code Issues Releases Wiki Activity

reader mode remembers scroll position when reloading

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Hakim El Hattab
2023-10-23 13:08:17 +02:00
parent ff3244af7a
commit aa5c03c234
5 changed files with 104 additions and 60 deletions
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2
dist/reveal.esm.js vendored
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dist/reveal.esm.js.map vendored
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dist/reveal.js vendored
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dist/reveal.js.map vendored
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156
js/controllers/reader.js
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@@ -42,7 +42,6 @@ export default class Reader {
const horizontalSlides = queryAll( this.Reveal.getRevealElement(), HORIZONTAL_SLIDES_SELECTOR );
this.viewportElement.classList.add( 'loading-scroll-mode', 'reveal-reader' );
this.viewportElement.addEventListener( 'scroll', this.onScroll, { passive: true } );
let presentationBackground;
@@ -134,11 +133,14 @@ export default class Reader {
this.Reveal.layout();
this.Reveal.setState( stateBeforeActivation );
this.viewportElement.classList.remove( 'loading-scroll-mode' );
this.activatedCallbacks.forEach( callback => callback() );
this.activatedCallbacks = [];
this.restoreScrollPosition();
this.viewportElement.classList.remove( 'loading-scroll-mode' );
this.viewportElement.addEventListener( 'scroll', this.onScroll, { passive: true } );
}
/**
@@ -253,7 +255,7 @@ export default class Reader {
if( this.isActive() ) {
this.syncPages();
this.onScroll();
this.syncScrollPosition();
}
}
@@ -587,6 +589,67 @@ export default class Reader {
}
/**
* Reads the current scroll position and updates our active
* trigger states accordingly.
*/
syncScrollPosition() {
const viewportHeight = this.viewportElement.offsetHeight;
const viewportHeightFactor = viewportHeight / this.viewportElement.scrollHeight;
const scrollTop = this.viewportElement.scrollTop;
const scrollHeight = this.viewportElement.scrollHeight - viewportHeight
const scrollProgress = Math.max( Math.min( scrollTop / scrollHeight, 1 ), 0 );
const scrollProgressMid = Math.max( Math.min( ( scrollTop + viewportHeight / 2 ) / this.viewportElement.scrollHeight, 1 ), 0 );
let activePage;
this.slideTriggers.forEach( ( trigger ) => {
const { page } = trigger;
const shouldPreload = scrollProgress >= trigger.range[0] - viewportHeightFactor*2 &&
scrollProgress <= trigger.range[1] + viewportHeightFactor*2;
// Load slides that are within the preload range
if( shouldPreload && !page.loaded ) {
page.loaded = true;
this.Reveal.slideContent.load( page.slideElement );
}
else if( page.loaded ) {
page.loaded = false;
this.Reveal.slideContent.unload( page.slideElement );
}
// If we're within this trigger range, activate it
if( scrollProgress >= trigger.range[0] && scrollProgress <= trigger.range[1] ) {
this.activateTrigger( trigger );
activePage = trigger.page;
}
// .. otherwise deactivate
else if( trigger.active ) {
this.deactivateTrigger( trigger );
}
} );
// Each page can have its own scroll triggers, check if any of those
// need to be activated/deactivated
if( activePage ) {
activePage.scrollTriggers.forEach( ( trigger ) => {
if( scrollProgressMid >= trigger.range[0] && scrollProgressMid <= trigger.range[1] ) {
this.activateTrigger( trigger );
}
else if( trigger.active ) {
this.deactivateTrigger( trigger );
}
} );
}
// Update our visual progress indication
this.setProgressBarValue( scrollTop / ( this.viewportElement.scrollHeight - viewportHeight ) );
}
/**
* Moves the progress bar playhead to the specified position.
*
@@ -657,6 +720,37 @@ export default class Reader {
}
/**
* Persists the current scroll position to session storage
* so that it can be restored.
*/
storeScrollPosition() {
clearTimeout( this.storeScrollPositionTimeout );
this.storeScrollPositionTimeout = setTimeout( () => {
sessionStorage.setItem( 'reveal-reader-scroll', this.viewportElement.scrollTop );
sessionStorage.setItem( 'reveal-reader-scroll-origin', location.origin + location.pathname );
this.storeScrollPositionTimeout = null;
}, 50 );
}
/**
* Restores the scroll position when a deck is reloader.
*/
restoreScrollPosition() {
const scrollPosition = sessionStorage.getItem( 'reveal-reader-scroll' );
const scrollOrigin = sessionStorage.getItem( 'reveal-reader-scroll-origin' );
if( scrollPosition && scrollOrigin === location.origin + location.pathname ) {
this.viewportElement.scrollTop = parseInt( scrollPosition, 10 );
}
}
/**
* Activates the given page and starts its embedded conten
* if there is any.
@@ -775,58 +869,8 @@ export default class Reader {
onScroll() {
const viewportHeight = this.viewportElement.offsetHeight;
const viewportHeightFactor = viewportHeight / this.viewportElement.scrollHeight;
const scrollTop = this.viewportElement.scrollTop;
const scrollHeight = this.viewportElement.scrollHeight - viewportHeight
const scrollProgress = Math.max( Math.min( scrollTop / scrollHeight, 1 ), 0 );
const scrollProgressMid = Math.max( Math.min( ( scrollTop + viewportHeight / 2 ) / this.viewportElement.scrollHeight, 1 ), 0 );
let activePage;
this.slideTriggers.forEach( ( trigger ) => {
const { page } = trigger;
const shouldPreload = scrollProgress >= trigger.range[0] - viewportHeightFactor*2 &&
scrollProgress <= trigger.range[1] + viewportHeightFactor*2;
// Load slides that are within the preload range
if( shouldPreload && !page.loaded ) {
page.loaded = true;
this.Reveal.slideContent.load( page.slideElement );
}
else if( page.loaded ) {
page.loaded = false;
this.Reveal.slideContent.unload( page.slideElement );
}
// If we're within this trigger range, activate it
if( scrollProgress >= trigger.range[0] && scrollProgress <= trigger.range[1] ) {
this.activateTrigger( trigger );
activePage = trigger.page;
}
// .. otherwise deactivate
else if( trigger.active ) {
this.deactivateTrigger( trigger );
}
} );
// Each page can have its own scroll triggers, check if any of those
// need to be activated/deactivated
if( activePage ) {
activePage.scrollTriggers.forEach( ( trigger ) => {
if( scrollProgressMid >= trigger.range[0] && scrollProgressMid <= trigger.range[1] ) {
this.activateTrigger( trigger );
}
else if( trigger.active ) {
this.deactivateTrigger( trigger );
}
} );
}
// Update our visual progress indication
this.setProgressBarValue( scrollTop / ( this.viewportElement.scrollHeight - viewportHeight ) );
this.syncScrollPosition();
this.storeScrollPosition();
}