Rationale:
- there was a lot of large objects passed by value, so potentially
there's a speed bump from this
- even for implicitly shared classes like QString/QList there's still
a (small) cost for copying the objects when there's no reason to
- it's the right thing to do!
is not applied
This could also have been fixed by changing from the activated
signal to currentIndexChanged for the indexChanged connection,
but it looks like activated was intentionally used here.
