For example - try to search for 'Discover' app in KRunner: 1. Start KRunner. 2. Type 'd' letter - no 'Discover' in search results. 3. Type 'i' letter - no 'Discover' in search results. 4. Type 's' letter - no 'Discover' in search results. 5. Type 'c' letter - Discover appears in search results. Expectations from search: Discover is appearing in search results right after typing of letter 'd'.
Well, if search term is too short we don't search through description and other fields, otherwise you end up with a ton of useless results that all just start with a "D". It's always a trade-off.
> if search term is too short What algorithm is used to determine "short"?
I think 3 letters or more could be a trigger for search or there can be an option for adjusting such functionality (possibly with minimal value of 3) - similarly to 'Minimal word length to complete' in Kate 'Auto Completion' settings
You should be using the new KStringHandler::logicalLength(string)>3 in KCoreAddons now. This should have done this in KRunner: https://phabricator.kde.org/D8771