From cb108696e62ffd54410297423b3aea0549ddcc84 Mon Sep 17 00:00:00 2001
From: Kitsune Ral <Kitsune-Ral@users.sf.net>
Date: Mon, 7 Nov 2016 13:08:13 +0900
Subject: Room::doAddNewMessages: Extend auto-promotion to all users, not only
 local

Thanks to @maralorn for pointing out.
---
 room.cpp | 32 ++++++++++++++++++++++++--------
 1 file changed, 24 insertions(+), 8 deletions(-)

diff --git a/room.cpp b/room.cpp
index 3d2e88c9..6c33cc58 100644
--- a/room.cpp
+++ b/room.cpp
@@ -505,19 +505,35 @@ void Room::doAddNewMessageEvents(const Events& events)
 {
     d->messageEvents.reserve(d->messageEvents.size() + events.size());
 
-    int newMessages = 0;
-    Event* latestLocalEventBeforeUnread = nullptr;
+    Timeline::size_type newUnreadMessages = 0;
+
+    // The first message in the batch defines whose read marker we can
+    // automatically promote any further. Others will need explicit read receipts
+    // from the server (or, for the local user, markMessagesAsRead() invocation)
+    // to promote their read markers over the new message events.
+    User* firstWriter = d->member(events.front()->senderId());
+    bool canAutoPromote = d->messageEvents.empty() ||
+            lastReadEvent(firstWriter) == d->messageEvents.back()->id();
+    Event* firstWriterSeriesEnd = canAutoPromote ? events.front() : nullptr;
+
     for (auto e: events)
     {
         d->messageEvents.push_back(e);
-        newMessages += d->isEventNotable(e);
-        if (!newMessages && e->senderId() == connection()->userId())
-            latestLocalEventBeforeUnread = e;
+
+        newUnreadMessages += d->isEventNotable(e);
+        if (firstWriterSeriesEnd)
+        {
+            if (e->senderId() != firstWriter->id())
+                firstWriterSeriesEnd = e;
+            else
+            {
+                setLastReadEvent(firstWriter, firstWriterSeriesEnd->id());
+                firstWriterSeriesEnd = nullptr;
+            }
+        }
     }
-    if (latestLocalEventBeforeUnread)
-        setLastReadEvent(d->connection->user(), latestLocalEventBeforeUnread->id());
 
-    if( !d->unreadMessages && newMessages > 0)
+    if( !d->unreadMessages && newUnreadMessages > 0)
     {
         d->unreadMessages = true;
         emit unreadMessagesChanged(this);
-- 
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