import React, { PureComponent } from 'react'; import PropTypes from 'prop-types'; import IntersectionObserverArticleContainer from '../containers/intersection_observer_article_container'; import LoadMore from './load_more'; import IntersectionObserverWrapper from '../features/ui/util/intersection_observer_wrapper'; import { throttle } from 'lodash'; import { List as ImmutableList } from 'immutable'; import classNames from 'classnames'; import LoadingIndicator from './loading_indicator'; const MOUSE_IDLE_DELAY = 300; export default class ScrollableList extends PureComponent { static contextTypes = { router: PropTypes.object, }; static propTypes = { scrollKey: PropTypes.string.isRequired, onLoadMore: PropTypes.func, isLoading: PropTypes.bool, showLoading: PropTypes.bool, hasMore: PropTypes.bool, prepend: PropTypes.node, alwaysPrepend: PropTypes.bool, emptyMessage: PropTypes.node, children: PropTypes.node, onScrollToTop: PropTypes.func, onScroll: PropTypes.func, }; state = { cachedMediaWidth: 250, // Default media/card width using default Gab Social theme }; intersectionObserverWrapper = new IntersectionObserverWrapper(); mouseIdleTimer = null; mouseMovedRecently = false; lastScrollWasSynthetic = false; scrollToTopOnMouseIdle = false; setScrollTop = newScrollTop => { if (this.documentElement.scrollTop !== newScrollTop) { this.lastScrollWasSynthetic = true; this.documentElement.scrollTop = newScrollTop; } }; clearMouseIdleTimer = () => { if (this.mouseIdleTimer === null) { return; } clearTimeout(this.mouseIdleTimer); this.mouseIdleTimer = null; }; handleMouseMove = throttle(() => { // As long as the mouse keeps moving, clear and restart the idle timer. this.clearMouseIdleTimer(); this.mouseIdleTimer = setTimeout(this.handleMouseIdle, MOUSE_IDLE_DELAY); if (!this.mouseMovedRecently && this.documentElement.scrollTop === 0) { // Only set if we just started moving and are scrolled to the top. this.scrollToTopOnMouseIdle = true; } // Save setting this flag for last, so we can do the comparison above. this.mouseMovedRecently = true; }, MOUSE_IDLE_DELAY / 2); handleMouseIdle = () => { if (this.scrollToTopOnMouseIdle) { this.setScrollTop(0); } this.mouseMovedRecently = false; this.scrollToTopOnMouseIdle = false; } componentDidMount () { this.window = window; this.documentElement = document.scrollingElement || document.documentElement; this.attachScrollListener(); this.attachIntersectionObserver(); // Handle initial scroll posiiton this.handleScroll(); } getScrollPosition = () => { if (this.documentElement && (this.documentElement.scrollTop > 0 || this.mouseMovedRecently)) { return { height: this.documentElement.scrollHeight, top: this.documentElement.scrollTop }; } else { return null; } } updateScrollBottom = (snapshot) => { const newScrollTop = this.documentElement.scrollHeight - snapshot; this.setScrollTop(newScrollTop); } componentDidUpdate (prevProps, prevState, snapshot) { // Reset the scroll position when a new child comes in in order not to // jerk the scrollbar around if you're already scrolled down the page. if (snapshot !== null) { this.setScrollTop(this.documentElement.scrollHeight - snapshot); } } attachScrollListener () { this.window.addEventListener('scroll', this.handleScroll); this.window.addEventListener('wheel', this.handleWheel); } detachScrollListener () { this.window.removeEventListener('scroll', this.handleScroll); this.window.removeEventListener('wheel', this.handleWheel); } handleScroll = throttle(() => { if (this.window) { const { scrollTop, scrollHeight } = this.documentElement; const { innerHeight } = this.window; const offset = scrollHeight - scrollTop - innerHeight; if (400 > offset && this.props.onLoadMore && this.props.hasMore && !this.props.isLoading) { this.props.onLoadMore(); } if (scrollTop < 100 && this.props.onScrollToTop) { this.props.onScrollToTop(); } else if (this.props.onScroll) { this.props.onScroll(); } if (!this.lastScrollWasSynthetic) { // If the last scroll wasn't caused by setScrollTop(), assume it was // intentional and cancel any pending scroll reset on mouse idle this.scrollToTopOnMouseIdle = false; } this.lastScrollWasSynthetic = false; } }, 150, { trailing: true, }); handleWheel = throttle(() => { this.scrollToTopOnMouseIdle = false; }, 150, { trailing: true, }); getSnapshotBeforeUpdate (prevProps) { const someItemInserted = React.Children.count(prevProps.children) > 0 && React.Children.count(prevProps.children) < React.Children.count(this.props.children) && this.getFirstChildKey(prevProps) !== this.getFirstChildKey(this.props); if (someItemInserted && (this.documentElement.scrollTop > 0 || this.mouseMovedRecently)) { return this.documentElement.scrollHeight - this.documentElement.scrollTop; } else { return null; } } cacheMediaWidth = (width) => { if (width && this.state.cachedMediaWidth !== width) { this.setState({ cachedMediaWidth: width }); } } componentWillUnmount () { this.clearMouseIdleTimer(); this.detachScrollListener(); this.detachIntersectionObserver(); } attachIntersectionObserver () { this.intersectionObserverWrapper.connect(); } detachIntersectionObserver () { this.intersectionObserverWrapper.disconnect(); } getFirstChildKey (props) { const { children } = props; let firstChild = children; if (children instanceof ImmutableList) { firstChild = children.get(0); } else if (Array.isArray(children)) { firstChild = children[0]; } return firstChild && firstChild.key; } handleLoadMore = e => { e.preventDefault(); this.props.onLoadMore(); } render () { const { children, scrollKey, showLoading, isLoading, hasMore, prepend, alwaysPrepend, emptyMessage, onLoadMore } = this.props; const childrenCount = React.Children.count(children); const trackScroll = true; //placeholder const loadMore = (hasMore && onLoadMore) ? : null; let scrollableArea = null; if (showLoading) { scrollableArea = (
{prepend}
); } else if (isLoading || childrenCount > 0 || hasMore || !emptyMessage) { scrollableArea = (
{prepend} {React.Children.map(this.props.children, (child, index) => ( {React.cloneElement(child, { getScrollPosition: this.getScrollPosition, updateScrollBottom: this.updateScrollBottom, cachedMediaWidth: this.state.cachedMediaWidth, cacheMediaWidth: this.cacheMediaWidth, })} ))} {loadMore}
); } else { scrollableArea = (
{alwaysPrepend && prepend}
{emptyMessage}
); } return scrollableArea; } }