We need a possibility to inform the QML side about events on the rust side. In traditional Qt these are signals (also properties but they have signals under the hood).

The currently suggested API is to use an attribute of the form

#[qsignal(cpp_name = "cppName")]
fn some_signal(&mut self, ...);

on the QML side we should be able to connect to onCppName with a connection.

The signal should be callable with common standard and Qt types as parameters and those should be usable on the QML side.