From db09d3d9e46f1013e9fe193394df632f6a9fd9e6 Mon Sep 17 00:00:00 2001
From: Richard van der Hoff <richard@matrix.org>
Date: Mon, 15 Feb 2016 09:50:12 +0000
Subject: [PATCH] Move ghost-read-marker logic to MessagePanel

---
 src/components/structures/MessagePanel.js  | 51 +++++++++++++++++-----
 src/components/structures/TimelinePanel.js |  3 --
 2 files changed, 39 insertions(+), 15 deletions(-)

diff --git a/src/components/structures/MessagePanel.js b/src/components/structures/MessagePanel.js
index f6c5cfc898..75ca902fc3 100644
--- a/src/components/structures/MessagePanel.js
+++ b/src/components/structures/MessagePanel.js
@@ -17,7 +17,7 @@ limitations under the License.
 var React = require('react');
 var sdk = require('../../index');
 
-/* stateless UI component which builds the event tiles in the room timeline.
+/* (almost) stateless UI component which builds the event tiles in the room timeline.
  */
 module.exports = React.createClass({
     displayName: 'MessagePanel',
@@ -35,10 +35,6 @@ module.exports = React.createClass({
         // event after which we should show a read marker
         readMarkerEventId: React.PropTypes.string,
 
-        // event after which we should show an animating disappearance of a
-        // read marker
-        readMarkerGhostEventId: React.PropTypes.string,
-
         // the userid of our user. This is used to suppress the read marker
         // for pending messages.
         ourUserId: React.PropTypes.string,
@@ -63,6 +59,17 @@ module.exports = React.createClass({
         onFillRequest: React.PropTypes.func,
     },
 
+    componentWillMount: function() {
+        // the event after which we put a visible unread marker on the last
+        // render cycle; null if readMarkerVisible was false or the RM was
+        // suppressed (eg because it was at the end of the timeline)
+        this.currentReadMarkerEventId = null;
+
+        // the event after which we are showing a disappearing read marker
+        // animation
+        this.currentGhostEventId = null;
+    },
+
     /* get the DOM node representing the given event */
     getNodeForEventId: function(eventId) {
         if (!this.eventNodes) {
@@ -158,11 +165,16 @@ module.exports = React.createClass({
             }
 
             var eventId = mxEv.getId();
-            if (eventId == this.props.readMarkerGhostEventId) {
-                ghostIndex = eventsToShow.length;
-            }
             if (eventId == this.props.readMarkerEventId) {
                 readMarkerIndex = eventsToShow.length;
+            } else if (eventId == this.currentReadMarkerEventId && !this.currentGhostEventId) {
+                // there is currently a read-up-to marker at this point, but no
+                // more. Show an animation of it disappearing.
+                ghostIndex = eventsToShow.length;
+                this.currentGhostEventId = eventId;
+            } else if (eventId == this.currentGhostEventId) {
+                // if we're showing an animation, continue to show it.
+                ghostIndex = eventsToShow.length;
             }
         }
 
@@ -170,6 +182,9 @@ module.exports = React.createClass({
 
         var prevEvent = null; // the last event we showed
 
+        // assume there is no read marker until proven otherwise
+        var readMarkerVisible = false;
+
         for (var i = 0; i < eventsToShow.length; i++) {
             var mxEv = eventsToShow[i];
             var wantTile = true;
@@ -183,6 +198,7 @@ module.exports = React.createClass({
                 // us sending a message and receiving the synthesized receipt.
                 if (mxEv.sender && mxEv.sender.userId != this.props.ourUserId) {
                     ret.push(this._getReadMarkerTile());
+                    readMarkerVisible = true;
                 }
             } else if (i == ghostIndex) {
                 ret.push(this._getReadMarkerGhostTile());
@@ -198,6 +214,7 @@ module.exports = React.createClass({
             prevEvent = mxEv;
         }
 
+        this.currentReadMarkerEventId = readMarkerVisible ? this.props.readMarkerEventId : null;
         return ret;
     },
 
@@ -259,17 +276,27 @@ module.exports = React.createClass({
     },
 
     _getReadMarkerGhostTile: function() {
-        var hr;
-        hr = <hr className="mx_RoomView_myReadMarker"
+        // reset the ghostEventId when the animation finishes, so that
+        // we can make a new one (and so that we don't run the
+        // animation code every time we render)
+        var completeFunc = () => {
+            this.currentGhostEventId = null;
+        };
+
+        var hr = <hr className="mx_RoomView_myReadMarker"
                   style={{opacity: 1, width: '99%'}}
                   ref={function(n) {
                         Velocity(n, {opacity: '0', width: '10%'},
                                     {duration: 400, easing: 'easeInSine',
-                                     delay: 1000});
+                                     delay: 1000, complete: completeFunc});
                   }}
             />;
+
+        // give it a key which depends on the event id. That will ensure that
+        // we get a new DOM node (restarting the animation) when the ghost
+        // moves to a different event.
         return (
-            <li key="_readuptoghost"
+            <li key={"_readuptoghost_"+this.currentGhostEventId}
                   className="mx_RoomView_myReadMarker_container">
                 {hr}
             </li>
diff --git a/src/components/structures/TimelinePanel.js b/src/components/structures/TimelinePanel.js
index 4b050bfed8..14da1e9ab8 100644
--- a/src/components/structures/TimelinePanel.js
+++ b/src/components/structures/TimelinePanel.js
@@ -82,7 +82,6 @@ module.exports = React.createClass({
             timelineLoading: true, // track whether our room timeline is loading
             canBackPaginate: true,
             readMarkerEventId: this._getCurrentReadReceipt(),
-            readMarkerGhostEventId: null,
         };
     },
 
@@ -200,7 +199,6 @@ module.exports = React.createClass({
 
         this.setState({
             readMarkerEventId: newReadMarker,
-            readMarkerGhostEventId: oldReadMarker,
         });
     },
 
@@ -441,7 +439,6 @@ module.exports = React.createClass({
                     events={ this.state.events }
                     highlightedEventId={ this.props.highlightedEventId }
                     readMarkerEventId={ this.state.readMarkerEventId }
-                    readMarkerGhostEventId={ this.state.readMarkerGhostEventId }
                     suppressFirstDateSeparator={ this.state.canBackPaginate }
                     ourUserId={ MatrixClientPeg.get().credentials.userId }
                     stickyBottom={ stickyBottom }