Merge pull request #2829 from matrix-org/travis/unread-button

Check if the message panel is at the end of the timeline on init

src/components/structures/RoomView.js

@@ -145,6 +145,7 @@ module.exports = React.createClass({
             // the end of the live timeline. It has the effect of hiding the
             // 'scroll to bottom' knob, among a couple of other things.
             atEndOfLiveTimeline: true,
+            atEndOfLiveTimelineInit: false, // used by componentDidUpdate to avoid unnecessary checks
 
             showTopUnreadMessagesBar: false,
 
@@ -429,6 +430,18 @@ module.exports = React.createClass({
                 roomView.addEventListener('dragend', this.onDragLeaveOrEnd);
             }
         }
+
+        // Note: We check the ref here with a flag because componentDidMount, despite
+        // documentation, does not define our messagePanel ref. It looks like our spinner
+        // in render() prevents the ref from being set on first mount, so we try and
+        // catch the messagePanel when it does mount. Because we only want the ref once,
+        // we use a boolean flag to avoid duplicate work.
+        if (this.refs.messagePanel && !this.state.atEndOfLiveTimelineInit) {
+            this.setState({
+                atEndOfLiveTimelineInit: true,
+                atEndOfLiveTimeline: this.refs.messagePanel.isAtEndOfLiveTimeline(),
+            });
+        }
     },
 
     componentWillUnmount: function() {