chatgui: add scroll-to-bottom floating button, incremental message refresh via getMessagesSince

tools/chatgui/src/messagelist.cpp

@@ -250,8 +250,39 @@ void MessageList::loadChannel(const QString& channelId) {
 }
 
 void MessageList::refresh() {
-    if (!m_currentChannelId.isEmpty())
-        loadChannel(m_currentChannelId);
+    if (m_currentChannelId.isEmpty() || !m_db || !m_db->isOpen()) return;
+
+    qint64 maxId = 0;
+    for (int r = 0; r < m_model->rowCount(); r++)
+        if (m_model->item(r)->data(MsgIdRole).toLongLong() > maxId)
+            maxId = m_model->item(r)->data(MsgIdRole).toLongLong();
+
+    auto newMsgs = m_db->getMessagesSince(m_currentChannelId, maxId);
+    if (newMsgs.isEmpty()) return;
+
+    QScrollBar* sb = m_view->verticalScrollBar();
+    bool wasAtBottom = sb && (sb->value() >= sb->maximum());
+
+    for (const auto& m : newMsgs) {
+        AccountRow acc = m_db->getAccount(m.authorNodeId);
+        QString author  = m_db->getDisplayName(m.authorNodeId);
+        QString letter  = acc.avatarLetter.isEmpty() ? author.mid(0, 1) : acc.avatarLetter;
+        QColor  color(acc.avatarColor);
+        if (!m_avatarCache.contains(m.authorNodeId))
+            m_avatarCache[m.authorNodeId] = color;
+        auto avatar = makeAvatar(color, letter);
+        auto time   = QDateTime::fromMSecsSinceEpoch(m.timestamp).toString("HH:mm");
+        auto *item = new QStandardItem();
+        setMsg(item, author, QString::fromUtf8(m.data), time, avatar, false,
+               false, QString(), QString(), QVariantList{});
+        item->setData(m.id, MsgIdRole);
+        m_model->appendRow(item);
+        while (m_model->rowCount() > 100)
+            m_model->removeRow(0);
+    }
+
+    if (wasAtBottom) m_view->scrollToBottom();
+    m_readDebounce->start();
 }
 
 void MessageList::addMessage(const QString& channelId, quint64 authorNodeId,