Use collection types for return values

[jf2048]

Is there a better way to get the actual type of a C array from the builder? The best I could do is adding the c_type like this.

I left the Vec<OsString> and Vec<PathBuf> return as is, since those require allocations and they are opt-in.

[sdroege]

Can you make a draft PR with the changes this causes in the generated code?

[sdroege]

What also might be worth considering here is parameters.

• transfer-none array parameters can be handled directly as &[T] for many types (shared, boxed, object) as long as the C function takes a length (i.e. does not require a NULL-terminated array)
• transfer-full collection parameters can be handled as exactly the underlying type
• For NULL-terminated string arrays there's impl IntoStrV (transfer-none) and StrV

This might also be something to handle in a separate PR though.

[jf2048]

Those should be handled in #1448

[sdroege]

Those should be handled in #1448

The first two fit more here or in a separate PR, or not? #1448 is string stuff, this here is collections :) The third one fits better in #1448 though, that's true.

[sdroege]

Looks good to me otherwise, if that wasn't clear. How should we proceed? :)

[jf2048]

Sorry for delay, I did some more testing and this is looking good for me too. But I think this situation should be resolved first: gtk-rs/gtk-rs-core#1078