Refactor TimelineView

Refactor TimelineView to make it more reliable and prepare for read marker choice. This is done by creating signalling from the mode when reset which can be used to move the scrollbar to the newest meassage.

Some of the spaghetti is also removed so there is no need for ChatBar and TimelineView to talk directly.

The code to mark messages as read if they are all visible after 10s has been removed infour of just marking as read on entry if all are visible. This is temporary until a follow up providing user options is finished (although it will be one of the options)

src/timeline/models/messagemodel.cpp

@@ -42,8 +42,10 @@ MessageModel::MessageModel(QObject *parent)
     });
 
     connect(this, &MessageModel::threadsEnabledChanged, this, [this]() {
+        Q_EMIT modelAboutToBeReset();
         beginResetModel();
         endResetModel();
+        Q_EMIT modelResetComplete();
     });
 }
 
@@ -60,6 +62,7 @@ void MessageModel::setRoom(NeoChatRoom *room)
 
     clearModel();
 
+    Q_EMIT modelAboutToBeReset();
     beginResetModel();
     m_room = room;
     if (m_room != nullptr) {
@@ -67,6 +70,7 @@ void MessageModel::setRoom(NeoChatRoom *room)
     }
     Q_EMIT roomChanged();
     endResetModel();
+    Q_EMIT modelResetComplete();
 }
 
 int MessageModel::timelineServerIndex() const
@@ -74,6 +78,11 @@ int MessageModel::timelineServerIndex() const
     return 0;
 }
 
+QPersistentModelIndex MessageModel::readMarkerIndex() const
+{
+    return m_lastReadEventIndex;
+}
+
 std::optional<std::reference_wrapper<const Quotient::RoomEvent>> MessageModel::getEventForIndex(QModelIndex index) const
 {
     Q_UNUSED(index)
@@ -342,18 +351,18 @@ QHash<int, QByteArray> MessageModel::roleNames() const
     return roles;
 }
 
-int MessageModel::eventIdToRow(const QString &eventID) const
+QModelIndex MessageModel::indexforEventId(const QString &eventId) const
 {
     if (m_room == nullptr) {
-        return -1;
+        return {};
     }
 
-    const auto it = m_room->findInTimeline(eventID);
+    const auto it = m_room->findInTimeline(eventId);
     if (it == m_room->historyEdge()) {
-        // qWarning() << "Trying to find inexistent event:" << eventID;
-        return -1;
+        qWarning() << "Trying to find non-existent event:" << eventId;
+        return {};
     }
-    return it - m_room->messageEvents().rbegin() + timelineServerIndex();
+    return index(it - m_room->messageEvents().rbegin() + timelineServerIndex());
 }
 
 void MessageModel::fullEventRefresh(int row)
@@ -455,6 +464,47 @@ void MessageModel::createEventObjects(const Quotient::RoomEvent *event)
     }
 }
 
+void MessageModel::moveReadMarker(const QString &toEventId)
+{
+    const auto timelineIt = m_room->findInTimeline(toEventId);
+    if (timelineIt == m_room->historyEdge()) {
+        return;
+    }
+    int newRow = int(timelineIt - m_room->messageEvents().rbegin()) + timelineServerIndex();
+
+    if (!m_lastReadEventIndex.isValid()) {
+        // Not valid index means we don't display any marker yet, in this case
+        // we create the new index and insert the row in case the read marker
+        // need to be displayed.
+        if (newRow > timelineServerIndex()) {
+            // The user didn't read all the messages yet.
+            beginInsertRows({}, newRow, newRow);
+            m_lastReadEventIndex = QPersistentModelIndex(index(newRow, 0));
+            endInsertRows();
+            Q_EMIT readMarkerIndexChanged();
+            Q_EMIT readMarkerAdded();
+            return;
+        }
+        // The user read all the messages and we didn't display any read marker yet
+        // => do nothing
+        return;
+    }
+    if (newRow <= timelineServerIndex()) {
+        // The user read all the messages => remove read marker
+        beginRemoveRows({}, m_lastReadEventIndex.row(), m_lastReadEventIndex.row());
+        m_lastReadEventIndex = QModelIndex();
+        endRemoveRows();
+        Q_EMIT readMarkerIndexChanged();
+        return;
+    }
+
+    // The user didn't read all the messages yet but moved the reader marker.
+    beginMoveRows({}, m_lastReadEventIndex.row(), m_lastReadEventIndex.row(), {}, newRow);
+    m_lastReadEventIndex = QPersistentModelIndex(index(newRow, 0));
+    endMoveRows();
+    Q_EMIT readMarkerIndexChanged();
+}
+
 void MessageModel::clearModel()
 {
     if (m_room) {
@@ -462,10 +512,12 @@ void MessageModel::clearModel()
 
         // HACK: Reset the model to a null room first to make sure QML dismantles
         // last room's objects before the room is actually changed
+        Q_EMIT modelAboutToBeReset();
         beginResetModel();
         m_room->disconnect(this);
         m_room = nullptr;
         endResetModel();
+        Q_EMIT modelResetComplete();
 
         // Because we don't want any of the object deleted before the model is cleared.
         oldRoom->setVisible(false);