glib: Ergonomics of 'Char' seem questionalble

[ids1024]

The docs suggest this is meant to be more ergonomic that taking libc:c_char. But is it an improvement over just accepting u8? Rust has a b'' syntax.

For the set_list_separator example in the documentation:

key_file.set_list_separator(glib::Char::new(';').unwrap());
key_file.set_list_separator(b';');
key_file.set_list_separator(';' as u8);

Apparently u8 doesn't implement TryFrom<char> (rust-lang/rfcs#2854), which would be useful for panicking behavior similar to glib::Char::new(...).unwrap() when out of range. But on the whole, accepting a u8 seems more ergonomic for most uses.

[ids1024]

For reference, libc::c_char seems to be i8 or u8 depending on the platform. I believe under the C standard a char has to be at least 8 bits, and sizeof(char) has to be 1, but it could technically be more than 8 bits. I doubt Rust or gtk are really usable on some bizarre hardware with bytes that aren't 8 bits though.

So it should be fine to use u8, which is the most natural type in Rust (given that b'' is interpreted as a u8).

[sdroege]

I agree, and also if we keep Char we should remove its constructor and make it a TryFrom impl instead.

@bilelmoussaoui @GuillaumeGomez ?

[GuillaumeGomez]

I'm fine with replacing Char constructor.

[sdroege]

@GuillaumeGomez What advantage over using u8 do you see that justifies the existence of the type? Not using it and directly using u8 seems easier in all cases I can think of.

[GuillaumeGomez]

Char is more explicit than u8. That's the only reason. We could use libc::c_char too but I find it less "nice".

[ids1024]

libc::c_char seems like an awkward type to use (except for ffi) since it could be a u8 or i8, and the b'' byte char syntax can only be used with u8.

So I guess glib::Char(b';') currently works on some platforms but fails to compile on others. So even if a newtype pattern like this is preferred, perhaps it should contain a u8 rather than c_char.

[GuillaumeGomez]

We can simply add a method on Char: fn new(c: u8) -> Self to make it coherent between platforms.

[sdroege]

So a TryFrom<char> for Char and a From<u8> for Char. Ok with me

[GuillaumeGomez]

👍