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Eliminate re-renders for intersection_observer_article.js (#5036)

rebase/4.0.0rc2
Nolan Lawson 2017-09-21 19:58:33 -07:00 committed by Eugen Rochko
parent 63819c848d
commit 245816ab27
1 changed files with 14 additions and 12 deletions
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26
app/javascript/mastodon/components/intersection_observer_article.js
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@ -1,10 +1,15 @@
import React from 'react'; import React from 'react';
import PropTypes from 'prop-types'; import PropTypes from 'prop-types';
import ImmutablePureComponent from 'react-immutable-pure-component';
import scheduleIdleTask from '../features/ui/util/schedule_idle_task'; import scheduleIdleTask from '../features/ui/util/schedule_idle_task';
import getRectFromEntry from '../features/ui/util/get_rect_from_entry'; import getRectFromEntry from '../features/ui/util/get_rect_from_entry';
import { is } from 'immutable';
export default class IntersectionObserverArticle extends ImmutablePureComponent { // 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 = { static propTypes = {
intersectionObserverWrapper: PropTypes.object.isRequired, intersectionObserverWrapper: PropTypes.object.isRequired,
@ -22,18 +27,15 @@ export default class IntersectionObserverArticle extends ImmutablePureComponent
} }
shouldComponentUpdate (nextProps, nextState) { shouldComponentUpdate (nextProps, nextState) {
if (!nextState.isIntersecting && nextState.isHidden) { const isUnrendered = !this.state.isIntersecting && (this.state.isHidden || this.props.cachedHeight);
// It's only if we're not intersecting (i.e. offscreen) and isHidden is true const willBeUnrendered = !nextState.isIntersecting && (nextState.isHidden || nextProps.cachedHeight);
// that either "isIntersecting" or "isHidden" matter, and then they're if (!!isUnrendered !== !!willBeUnrendered) {
// the only things that matter (and updated ARIA attributes). // If we're going from rendered to unrendered (or vice versa) then update
return this.state.isIntersecting || !this.state.isHidden || nextProps.listLength !== this.props.listLength;
} else if (nextState.isIntersecting && !this.state.isIntersecting) {
// If we're going from a non-intersecting state to an intersecting state,
// (i.e. offscreen to onscreen), then we definitely need to re-render
return true; return true;
} }
// Otherwise, diff based on "updateOnProps" and "updateOnStates" // Otherwise, diff based on props
return super.shouldComponentUpdate(nextProps, nextState); const propsToDiff = isUnrendered ? updateOnPropsForUnrendered : updateOnPropsForRendered;
return !propsToDiff.every(prop => is(nextProps[prop], this.props[prop]));
} }
componentDidMount () { componentDidMount () {