Structs reactivity in slit and c++ side

[hellozyemlya]

Starting learning slint, looks very interesting. Trying to get some feedback from c++ side. I learned that props can be changed, that there is model, where I can add-remove items. But structs... They are copied between slint and cpp realms, right? In slit structs are "reactive" just like properties, but if I try to runwin->get_my_struct().somefield = "123", no changes applied on slit side. Is that intended? So If I have list of models, and I need to alter them in c++, I need to change whole struct entirely, right?

Also, if structs is not reactive in c++, I may suppose that structs is not the best way to store reactive data in slit side as well? Or that somehow handled?

[hellozyemlya]

Also, in javascript react world there is an approach with immutable state. If you have some model, and if any model leaf changed, you recreate whole model, copying non-changed fields, replacing changed, starting from leaf to model root. So state management library can track what components to re-render. Is that approach will work well on slint? Or setting big struct will re-trigger too much calculations?

[csavels]

In rust:
win->get_my_struct().set_somefield (123)
Perhaps the same ;)

[ogoffart]

The get_my_struct() returns a copy of the struct in a temporary. So changing it won't work.
What works is:

auto s = win->get_my_struct();
s.somefield = "123";
win->set_my_struct(s);