import React from 'react'; import PropTypes from 'prop-types'; import ImmutablePureComponent from 'react-immutable-pure-component'; import scheduleIdleTask from 'flavours/glitch/util/schedule_idle_task'; import getRectFromEntry from 'flavours/glitch/util/get_rect_from_entry'; export default class IntersectionObserverArticle extends ImmutablePureComponent { 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) { if (!nextState.isIntersecting && nextState.isHidden) { // It's only if we're not intersecting (i.e. offscreen) and isHidden is true // that either "isIntersecting" or "isHidden" matter, and then they're // the only things that matter (and updated ARIA attributes). 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; } // Otherwise, diff based on "updateOnProps" and "updateOnStates" return super.shouldComponentUpdate(nextProps, nextState); } 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 && !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} 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} aria-setsize={listLength} data-id={id} tabIndex='0'> {children && React.cloneElement(children, { hidden: false })} </article> ); } }