* Note that this method performs a binary search, hence it has as complexity of O(log n).
* If matchExact is false, and we don't have an exact match for the given msgId, we return the visible line right
* above the requested one.
* \param msgId The message ID to look for
* \param matchExact Whether we find only exact matches
* Note that this method performs a binary search, hence it has as complexity of O(log n).
* If matchExact is false, and we don't have an exact match for the given msgId, we return the visible line right
* above the requested one.
* \param msgId The message ID to look for
* \param matchExact Whether we find only exact matches