client: Fix backlog requests with 0 initial fetch

If no available messages in a buffer exist, try fetching the newest
messages.  This fixes requesting additional backlog for a buffer when
the initial backlog fetching has been disabled (set to zero).

diff --git a/src/client/messagemodel.cpp b/src/client/messagemodel.cpp
index 76914bf..6c88721 100644 (file)
--- a/src/client/messagemodel.cpp
+++ b/src/client/messagemodel.cpp
@@ -393,17 +393,35 @@ void MessageModel::requestBacklog(BufferId bufferId)
     BacklogSettings backlogSettings;
     int requestCount = backlogSettings.dynamicBacklogAmount();
 
+    // Assume there's no available messages
+    MsgId oldestAvailableMsgId{-1};
+
+    // Try to find the oldest (lowest ID) message belonging to this buffer
     for (int i = 0; i < messageCount(); i++) {
         if (messageItemAt(i)->bufferId() == bufferId) {
-            _messagesWaiting[bufferId] = requestCount;
-            Client::backlogManager()->emitMessagesRequested(tr("Requesting %1 messages from backlog for buffer %2:%3")
-                                                                .arg(requestCount)
-                                                                .arg(Client::networkModel()->networkName(bufferId))
-                                                                .arg(Client::networkModel()->bufferName(bufferId)));
-            Client::backlogManager()->requestBacklog(bufferId, -1, messageItemAt(i)->msgId(), requestCount);
-            return;
+            // Match found, use this message ID for requesting more backlog
+            oldestAvailableMsgId = messageItemAt(i)->msgId();
+            break;
         }
     }
+
+    // Prepare to fetch messages
+    _messagesWaiting[bufferId] = requestCount;
+    Client::backlogManager()->emitMessagesRequested(tr("Requesting %1 messages from backlog for buffer %2:%3")
+                                                        .arg(requestCount)
+                                                        .arg(Client::networkModel()->networkName(bufferId))
+                                                        .arg(Client::networkModel()->bufferName(bufferId)));
+
+    if (oldestAvailableMsgId.isValid()) {
+        // Request messages from backlog starting from this message ID, going into the past
+        Client::backlogManager()->requestBacklog(bufferId, -1, oldestAvailableMsgId, requestCount);
+    }
+    else {
+        // No existing messages could be found.  Try to fetch the newest available messages instead.
+        // This may happen when initial backlog fetching is set to zero, or if no messages exist in
+        // a buffer.
+        Client::backlogManager()->requestBacklog(bufferId, -1, -1, requestCount);
+    }
 }
 
 void MessageModel::messagesReceived(BufferId bufferId, int count)