Merge pull request #362 from ThibG/glitch-soc/fix-notifications-clearing

Revert 245816ab27 (fixes #348)

app/javascript/flavours/glitch/components/intersection_observer_article.js

@@ -1,15 +1,10 @@
 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';
-import { is } from 'immutable';
 
-// 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 {
+export default class IntersectionObserverArticle extends ImmutablePureComponent {
 
   static propTypes = {
     intersectionObserverWrapper: PropTypes.object.isRequired,
@@ -27,15 +22,18 @@ export default class IntersectionObserverArticle extends React.Component {
   }
 
   shouldComponentUpdate (nextProps, nextState) {
-    const isUnrendered = !this.state.isIntersecting && (this.state.isHidden || this.props.cachedHeight);
-    const willBeUnrendered = !nextState.isIntersecting && (nextState.isHidden || nextProps.cachedHeight);
-    if (!!isUnrendered !== !!willBeUnrendered) {
-      // If we're going from rendered to unrendered (or vice versa) then update
+    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 props
-    const propsToDiff = isUnrendered ? updateOnPropsForUnrendered : updateOnPropsForRendered;
-    return !propsToDiff.every(prop => is(nextProps[prop], this.props[prop]));
+    // Otherwise, diff based on "updateOnProps" and "updateOnStates"
+    return super.shouldComponentUpdate(nextProps, nextState);
   }
 
   componentDidMount () {