hometown/app/javascript/mastodon/components/intersection_observer_article.js
ThibG d09ce6d81b Fix IntersectionObserverArticle not hiding some out-of-view items (#9982)
IntersectionObserverArticle is made to save on RAM by avoiding fully rendering
items that are far out of view. However, it did not work for items spawned
outside the intersection observer.
2019-02-06 23:36:43 +01:00

131 lines
4.2 KiB
JavaScript

import React from 'react';
import PropTypes from 'prop-types';
import scheduleIdleTask from '../features/ui/util/schedule_idle_task';
import getRectFromEntry from '../features/ui/util/get_rect_from_entry';
import { is } from 'immutable';
// Diff these props in the "rendered" state
const updateOnPropsForRendered = ['id', 'index', 'listLength'];
// Diff these props in the "unrendered" state
const updateOnPropsForUnrendered = ['id', 'index', 'listLength', 'cachedHeight'];
export default class IntersectionObserverArticle extends React.Component {
static propTypes = {
intersectionObserverWrapper: PropTypes.object.isRequired,
id: PropTypes.oneOfType([PropTypes.string, PropTypes.number]),
index: PropTypes.oneOfType([PropTypes.string, PropTypes.number]),
listLength: PropTypes.oneOfType([PropTypes.string, PropTypes.number]),
saveHeightKey: PropTypes.string,
cachedHeight: PropTypes.number,
onHeightChange: PropTypes.func,
children: PropTypes.node,
};
state = {
isHidden: false, // set to true in requestIdleCallback to trigger un-render
}
shouldComponentUpdate (nextProps, nextState) {
const isUnrendered = !this.state.isIntersecting && (this.state.isHidden || this.props.cachedHeight);
const willBeUnrendered = !nextState.isIntersecting && (nextState.isHidden || nextProps.cachedHeight);
if (!!isUnrendered !== !!willBeUnrendered) {
// If we're going from rendered to unrendered (or vice versa) then update
return true;
}
// Otherwise, diff based on props
const propsToDiff = isUnrendered ? updateOnPropsForUnrendered : updateOnPropsForRendered;
return !propsToDiff.every(prop => is(nextProps[prop], this.props[prop]));
}
componentDidMount () {
const { intersectionObserverWrapper, id } = this.props;
intersectionObserverWrapper.observe(
id,
this.node,
this.handleIntersection
);
this.componentMounted = true;
}
componentWillUnmount () {
const { intersectionObserverWrapper, id } = this.props;
intersectionObserverWrapper.unobserve(id, this.node);
this.componentMounted = false;
}
handleIntersection = (entry) => {
this.entry = entry;
scheduleIdleTask(this.calculateHeight);
this.setState(this.updateStateAfterIntersection);
}
updateStateAfterIntersection = (prevState) => {
if (prevState.isIntersecting !== false && !this.entry.isIntersecting) {
scheduleIdleTask(this.hideIfNotIntersecting);
}
return {
isIntersecting: this.entry.isIntersecting,
isHidden: false,
};
}
calculateHeight = () => {
const { onHeightChange, saveHeightKey, id } = this.props;
// save the height of the fully-rendered element (this is expensive
// on Chrome, where we need to fall back to getBoundingClientRect)
this.height = getRectFromEntry(this.entry).height;
if (onHeightChange && saveHeightKey) {
onHeightChange(saveHeightKey, id, this.height);
}
}
hideIfNotIntersecting = () => {
if (!this.componentMounted) {
return;
}
// When the browser gets a chance, test if we're still not intersecting,
// and if so, set our isHidden to true to trigger an unrender. The point of
// this is to save DOM nodes and avoid using up too much memory.
// See: https://github.com/tootsuite/mastodon/issues/2900
this.setState((prevState) => ({ isHidden: !prevState.isIntersecting }));
}
handleRef = (node) => {
this.node = node;
}
render () {
const { children, id, index, listLength, cachedHeight } = this.props;
const { isIntersecting, isHidden } = this.state;
if (!isIntersecting && (isHidden || cachedHeight)) {
return (
<article
ref={this.handleRef}
aria-posinset={index + 1}
aria-setsize={listLength}
style={{ height: `${this.height || cachedHeight}px`, opacity: 0, overflow: 'hidden' }}
data-id={id}
tabIndex='0'
>
{children && React.cloneElement(children, { hidden: true })}
</article>
);
}
return (
<article ref={this.handleRef} aria-posinset={index + 1} aria-setsize={listLength} data-id={id} tabIndex='0'>
{children && React.cloneElement(children, { hidden: false })}
</article>
);
}
}