Try to fix flickering, if sync return event before send completes

src/EventAccessors.cpp

@@ -207,6 +207,20 @@ struct EventInReplyTo
         }
 };
 
+struct EventTransactionId
+{
+        template<class T>
+        std::string operator()(const mtx::events::RoomEvent<T> &e)
+        {
+                return e.unsigned_data.transaction_id;
+        }
+        template<class T>
+        std::string operator()(const mtx::events::Event<T> &e)
+        {
+                return e.unsigned_data.transaction_id;
+        }
+};
+
 struct EventMediaHeight
 {
         template<class Content>
@@ -344,6 +358,12 @@ mtx::accessors::in_reply_to_event(const mtx::events::collections::TimelineEvents
         return std::visit(EventInReplyTo{}, event);
 }
 
+std::string
+mtx::accessors::transaction_id(const mtx::events::collections::TimelineEvents &event)
+{
+        return std::visit(EventTransactionId{}, event);
+}
+
 int64_t
 mtx::accessors::filesize(const mtx::events::collections::TimelineEvents &event)
 {

src/EventAccessors.h

@@ -50,6 +50,8 @@ std::string
 mimetype(const mtx::events::collections::TimelineEvents &event);
 std::string
 in_reply_to_event(const mtx::events::collections::TimelineEvents &event);
+std::string
+transaction_id(const mtx::events::collections::TimelineEvents &event);
 
 int64_t
 filesize(const mtx::events::collections::TimelineEvents &event);

src/timeline/TimelineModel.cpp

@@ -538,6 +538,20 @@ TimelineModel::internalAddEvents(
                         continue;
                 }
 
+                QString txid = QString::fromStdString(mtx::accessors::transaction_id(e));
+                if (this->pending.removeOne(txid)) {
+                        this->events.insert(id, e);
+                        this->events.remove(txid);
+                        int idx = idToIndex(txid);
+                        if (idx < 0) {
+                                nhlog::ui()->warn("Received index out of range");
+                                continue;
+                        }
+                        eventOrder[idx] = id;
+                        emit dataChanged(index(idx, 0), index(idx, 0));
+                        continue;
+                }
+
                 if (auto redaction =
                       std::get_if<mtx::events::RedactionEvent<mtx::events::msg::Redaction>>(&e)) {
                         QString redacts = QString::fromStdString(redaction->redacts);