How to set Box<dyn tr::Translator> for a slint app in Rust?

[tadeohepperle]

We would like to make a custom implementation of tr::Translator because we have dynamic content that needs translation which is not well served by e.g. GetText.

But how do we configure the translator for the slint app in Rust? Can it be configured via the BackendSelector? And what features need to be enabled to use it?

For Python there seems to be the following function:

fn init_translations(_py: Python<'_>, translations: Bound<PyAny>) -> PyResult<()> {
    i_slint_backend_selector::with_global_context(|ctx| {
        ctx.set_external_translator(if translations.is_none() {
            None
        } else {
            Some(Box::new(PyGettextTranslator(translations.unbind())))
        });
    })
    .map_err(|e| errors::PyPlatformError(e))?;
    Ok(())
}

We'd like to do something similar but using the Rust interface of slint.

[ogoffart]

We currently do not have a public API to do that.

This is tracked in issue #3715

All we need to do is to decide on the API.
We would need to decide if we expose tr::Translator directly or wrap it in another trait.