import { is } from 'immutable' import { setHeight } from '../actions/height_cache' import scheduleIdleTask from '../utils/schedule_idle_task' import getRectFromEntry from '../utils/get_rect_from_entry' // 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'] const makeMapStateToProps = (state, props) => ({ cachedHeight: state.getIn(['height_cache', props.saveHeightKey, props.id]), }) const mapDispatchToProps = (dispatch) => ({ onHeightChange(key, id, height) { dispatch(setHeight(key, id, height)) }, }) export default @connect(makeMapStateToProps, mapDispatchToProps) 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 = { isIntersecting: false, isHidden: false, } 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; } shouldComponentUpdate(nextProps, nextState) { const isUnrendered = !this.state.isIntersecting && (this.state.isHidden || this.props.cachedHeight); const willBeUnrendered = !nextState.isIntersecting && (nextState.isHidden || nextProps.cachedHeight); // If we're going from rendered to unrendered (or vice versa) then update if (!!isUnrendered !== !!willBeUnrendered) { return true; } // Otherwise, diff based on props const propsToDiff = isUnrendered ? updateOnPropsForUnrendered : updateOnPropsForRendered; return !propsToDiff.every(prop => is(nextProps[prop], this.props[prop])); } 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 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 (
{React.cloneElement(children, { isHidden: true, cachedHeight })}
) } return (
{React.cloneElement(children, { isHidden: false, isIntersecting, cachedHeight })}
) } }