Move gl device implementation into separate crate

[brendanzab]

I am having trouble understanding it. It would be great if it were more decoupled from the common device interface.

[emberian]

This is going to involve some heavy refactoring, and I think it should wait until Rust has associated types. The problem is that the BackEnd implementation conceptually defines all of the types that are needed to interact with it, but the trait itself lives in device. So, device needs types from the backend, the backend needs the trait from device... it's more than the trait, though, it's most of the API. Without associated types, can't make any progress.

[brendanzab]

Could we create a mocked up trait specification to allow us to transition in the future?

[emberian]

@bjz I believe this is done, currently.

[brendanzab]

It isn't - it is currently in a separate directory, but not actually a separate crate: https://github.com/gfx-rs/gfx-rs/blob/master/src/device/lib.rs#L43

[emberian]

Ah, yes.

[kvark]

@bjz I believe you are working on this one?
Edit: is it still blocked?

[brendanzab]

I was working on it, but was blocked by the associated item stuff.

[kvark]

Posting your comment, assuming it was about this issue:

Arg, trying to get associated types working with handles
but I am running into issues
I end up needing to pass the Device as a type parameter around
and the CommandBuffer trait needs the handle types
so CommandBuffer needs Device as a type parameter
but that ends in type checker recursion and blowing up rustc's stack
😔

[kvark]

@bjz So you are running into a type dependency recursion? Come back to gitter, when you have a moment, to share more info. Perhaps, you could push your branch for me to check out.