qml can not recognize the c++ parameters with &

[anda_skoa]

I hope so, but it is QList<QUrl> but not QList<QString>

I see, should still be ok. Your slot has the same type for its arguments.

Hard to said, because I need to modify the content of QList(sorting)

Depends on the reference count at the time of modification. If the slot is the only one holding the list at that time it won't need to copy.
If there is another owner, then there will be a copy of the list. Since you don't change the url data the QUrl instances should still be the same.

No, it is not a bottleneck yet(maybe in the future, it is)
but the experience from c++(and c) make me feel nervous
when I have to copy the data which could be "moved" or take the reference usually

Due to the implicit sharing, copying is a lot like moving, actual copying happening on modification (copy on write).

Cheers,
_