Clarify if and when data is copied when passed between C++ and QML/JS

When passing a QList<ValueType> from C++ to QML, does the list get copied? We don't eagerly construct a JS array in QML, so one should probably get a QV4::SequenceWrapper wrapping the QList, and that will use implicit sharing, so the QList is also not copied.

But are there scenarios where this doesn't work? What happens on the other way around (Java array with value types sent to C++ through an invokable)?