From c9b547368b3a404d1f183dddc00e5d6c02a1be14 Mon Sep 17 00:00:00 2001
From: Michael Telatynski <7t3chguy@gmail.com>
Date: Sat, 22 Jul 2017 13:10:57 +0100
Subject: [PATCH] add algo to ensure that RM always moves forwards

this is needed so that if a client which does not hide any events
sets and RM at bottom of timeline, then riot-web which hides events
sets the RM it'd set it at X-N where X is bottom and N is the amount of
hidden events at bottom of the timeline, this way now an RM will
fall through to the hidden events below a seen event.

Signed-off-by: Michael Telatynski <7t3chguy@gmail.com>
---
 src/components/structures/TimelinePanel.js | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/src/components/structures/TimelinePanel.js b/src/components/structures/TimelinePanel.js
index 0aee19545c..b07b975b5e 100644
--- a/src/components/structures/TimelinePanel.js
+++ b/src/components/structures/TimelinePanel.js
@@ -1020,7 +1020,14 @@ var TimelinePanel = React.createClass({
             var boundingRect = node.getBoundingClientRect();
             if ((allowPartial && boundingRect.top < wrapperRect.bottom) ||
                 (!allowPartial && boundingRect.bottom < wrapperRect.bottom)) {
-                return i;
+                let latestReadEventIndex = i;
+                // Place the RM at a hidden event below the latest seen event (if exists)
+                // to prevent RM going up the timeline between clients which do not hide the same events.
+                for (let j = i; j < this.state.events.length; ++j) {
+                    if (messagePanel._shouldShowEvent(this.state.events[j])) break;
+                    latestReadEventIndex = j;
+                }
+                return latestReadEventIndex;
             }
         }
         return null;