Create view! equivalent macro for buildable files to create AsyncComponent

[trutas83]

Currently, there's no good way to create widgets with .ui files when creating AsyncComponent. This can be done with Components using gtk directly, but the same method cannot be used for AsyncComponent since async traits aren't officially supported.

[AaronErhardt]

Relm4 re-exports the async_trait crate: https://docs.rs/relm4/latest/relm4/index.html#reexport.async_trait

All you need to do is to use #[relm4::async_trait::async_trait] above your AsyncComponent impl.

[trutas83]

Ah, I'm pretty new to Rust, and I didn't know what re-exports are for. Learned a new thing.

I still think it'd be helpful if there's a macro that generates widgets using .ui files.

Really cool project, by the way. Nice work!

[AaronErhardt]

I still think it'd be helpful if there's a macro that generates widgets using .ui files.

I think gtk-rs has a macro for this, doesn't it? But I'm open for ideas or examples for using .ui files in Relm4. It's just that most people use the view! macro so we don't get a lot of requests or feedback regarding .ui files.

[trutas83]

I think gtk-rs has a macro for this, doesn't it?

Hmm. I'm not aware of any macro that leverages .ui files, but I could be wrong.

It's just that most people use the view! macro so we don't get a lot of requests or feedback regarding .ui files.

That makes sense. It's just that .ui files are independent to programming languages so reusing widgets is easier. Not to mention that version migrations are trivial with conversion tools.