Generalized the infinite scrollable list (#4697)

1 files changed, 179 insertions, 0 deletions

diff --git a/app/javascript/mastodon/components/scrollable_list.js b/app/javascript/mastodon/components/scrollable_list.js
new file mode 100644
index 000000000..1a122dbe5
--- /dev/null
+++ b/app/javascript/mastodon/components/scrollable_list.js
@@ -0,0 +1,179 @@
+import React, { PureComponent } from 'react';
+import { ScrollContainer } from 'react-router-scroll';
+import PropTypes from 'prop-types';
+import IntersectionObserverArticle from './intersection_observer_article';
+import LoadMore from './load_more';
+import IntersectionObserverWrapper from '../features/ui/util/intersection_observer_wrapper';
+import { throttle } from 'lodash';
+
+export default class ScrollableList extends PureComponent {
+
+  static propTypes = {
+    scrollKey: PropTypes.string.isRequired,
+    onScrollToBottom: PropTypes.func,
+    onScrollToTop: PropTypes.func,
+    onScroll: PropTypes.func,
+    trackScroll: PropTypes.bool,
+    shouldUpdateScroll: PropTypes.func,
+    isLoading: PropTypes.bool,
+    hasMore: PropTypes.bool,
+    prepend: PropTypes.node,
+    emptyMessage: PropTypes.node,
+    children: PropTypes.node,
+  };
+
+  static defaultProps = {
+    trackScroll: true,
+  };
+
+  intersectionObserverWrapper = new IntersectionObserverWrapper();
+
+  handleScroll = throttle(() => {
+    if (this.node) {
+      const { scrollTop, scrollHeight, clientHeight } = this.node;
+      const offset = scrollHeight - scrollTop - clientHeight;
+      this._oldScrollPosition = scrollHeight - scrollTop;
+
+      if (400 > offset && this.props.onScrollToBottom && !this.props.isLoading) {
+        this.props.onScrollToBottom();
+      } else if (scrollTop < 100 && this.props.onScrollToTop) {
+        this.props.onScrollToTop();
+      } else if (this.props.onScroll) {
+        this.props.onScroll();
+      }
+    }
+  }, 150, {
+    trailing: true,
+  });
+
+  componentDidMount () {
+    this.attachScrollListener();
+    this.attachIntersectionObserver();
+
+    // Handle initial scroll posiiton
+    this.handleScroll();
+  }
+
+  componentDidUpdate (prevProps) {
+    // 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 (React.Children.count(prevProps.children) < React.Children.count(this.props.children) && this._oldScrollPosition && this.node.scrollTop > 0) {
+      if (this.getFirstChildKey(prevProps) !== this.getFirstChildKey(this.props)) {
+        const newScrollTop = this.node.scrollHeight - this._oldScrollPosition;
+        if (this.node.scrollTop !== newScrollTop) {
+          this.node.scrollTop = newScrollTop;
+        }
+      } else {
+        this._oldScrollPosition = this.node.scrollHeight - this.node.scrollTop;
+      }
+    }
+  }
+
+  componentWillUnmount () {
+    this.detachScrollListener();
+    this.detachIntersectionObserver();
+  }
+
+  attachIntersectionObserver () {
+    this.intersectionObserverWrapper.connect({
+      root: this.node,
+      rootMargin: '300% 0px',
+    });
+  }
+
+  detachIntersectionObserver () {
+    this.intersectionObserverWrapper.disconnect();
+  }
+
+  attachScrollListener () {
+    this.node.addEventListener('scroll', this.handleScroll);
+  }
+
+  detachScrollListener () {
+    this.node.removeEventListener('scroll', this.handleScroll);
+  }
+
+  getFirstChildKey (props) {
+    const { children } = props;
+    const firstChild = Array.isArray(children) ? children[0] : children;
+    return firstChild && firstChild.key;
+  }
+
+  setRef = (c) => {
+    this.node = c;
+  }
+
+  handleLoadMore = (e) => {
+    e.preventDefault();
+    this.props.onScrollToBottom();
+  }
+
+  handleKeyDown = (e) => {
+    if (['PageDown', 'PageUp'].includes(e.key) || (e.ctrlKey && ['End', 'Home'].includes(e.key))) {
+      const article = (() => {
+        switch (e.key) {
+        case 'PageDown':
+          return e.target.nodeName === 'ARTICLE' && e.target.nextElementSibling;
+        case 'PageUp':
+          return e.target.nodeName === 'ARTICLE' && e.target.previousElementSibling;
+        case 'End':
+          return this.node.querySelector('[role="feed"] > article:last-of-type');
+        case 'Home':
+          return this.node.querySelector('[role="feed"] > article:first-of-type');
+        default:
+          return null;
+        }
+      })();
+
+
+      if (article) {
+        e.preventDefault();
+        article.focus();
+        article.scrollIntoView();
+      }
+    }
+  }
+
+  render () {
+    const { children, scrollKey, trackScroll, shouldUpdateScroll, isLoading, hasMore, prepend, emptyMessage } = this.props;
+    const childrenCount = React.Children.count(children);
+
+    const loadMore     = <LoadMore visible={!isLoading && childrenCount > 0 && hasMore} onClick={this.handleLoadMore} />;
+    let scrollableArea = null;
+
+    if (isLoading || childrenCount > 0 || !emptyMessage) {
+      scrollableArea = (
+        <div className='scrollable' ref={this.setRef}>
+          <div role='feed' className='item-list' onKeyDown={this.handleKeyDown}>
+            {prepend}
+
+            {React.Children.map(this.props.children, (child, index) => (
+              <IntersectionObserverArticle key={child.key} id={child.key} index={index} listLength={childrenCount} intersectionObserverWrapper={this.intersectionObserverWrapper}>
+                {child}
+              </IntersectionObserverArticle>
+            ))}
+
+            {loadMore}
+          </div>
+        </div>
+      );
+    } else {
+      scrollableArea = (
+        <div className='empty-column-indicator' ref={this.setRef}>
+          {emptyMessage}
+        </div>
+      );
+    }
+
+    if (trackScroll) {
+      return (
+        <ScrollContainer scrollKey={scrollKey} shouldUpdateScroll={shouldUpdateScroll}>
+          {scrollableArea}
+        </ScrollContainer>
+      );
+    } else {
+      return scrollableArea;
+    }
+  }
+
+}