Support for raw-window-handle

[ghost]

Taking off from #910: @Lokathor provided some system-specific bindings and I've plucked out the necessary stuff to make this run on macOS, linux, and windows. This definitely runs on macOS, but I was unable to procure linux and windows machines to verify support there. I'm confident it "should work", though.

[Cobrand]

Can you add a test, or an example, so that we can check it works on every platform?

Also, a mention of this feature in the README would be appreciated. People have no way to know there is such a feature unless they manually look in the Cargo.toml.

[ghost]

@Cobrand I've adding tests for each platform and an example working with wgpu. I had to add a few test dependencies to get the example going, though. Let me know what you think!

[Cobrand]

I'd gladly merge this but the example and the test don't compile on my machine on linux.

Here is the error message:

error: cannot find macro `log` in this scope
  --> /home/cobrand/.cargo/registry/src/github.com-1ecc6299db9ec823/relevant-0.4.2/src/lib.rs:72:13
   |
72 |             sink!("Values of this type can't be dropped!")
   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ in this macro invocation
   |
   = note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)

error: aborting due to previous error

error: could not compile `relevant`.

Looks like the relevant crate is causing issues, but when I compile it manually the issue doesn't arise... Really weird.

[ghost]

I'm not sure what's wrong. I was able to get the example to compile with no issues on clean ubuntu and arch installs. What distro are you using?

[Cobrand]

I'm using archlinux, but that should be irrelevant.

I tried deleting my Cargo.lock, and this time I got this error, which comes from the example:

error[E0432]: unresolved import `raw_window_handle::macos`
  --> examples/raw-window-handle-with-wgpu/main.rs:14:24
   |
14 | use raw_window_handle::macos::MacOSHandle;
   |                        ^^^^^ could not find `macos` in `raw_window_handle`

error: aborting due to previous error

A conditional import should do the trick here.

[ghost]

Bah, I've been burned by IDE auto-imports before. I moved it to where it's actually used.

[Cobrand]

I got a panic inside the wgpu lib now:

thread 'main' panicked at 'called `Option::unwrap()` on a `None` value'
...
16: wgpu_request_adapter
             at /home/cobrand/.cargo/registry/src/github.com-1ecc6299db9ec823/wgpu-native-0.4.3/src/instance.rs:474
  17: wgpu::Adapter::request
             at /home/cobrand/.cargo/registry/src/github.com-1ecc6299db9ec823/wgpu-0.4.0/src/lib.rs:545
  18: raw_window_handle_with_wgpu::main
             at examples/raw-window-handle-with-wgpu/main.rs:67
...

I think it's unrelated to this PR (or at least your PR isn't the cause) and I'm ready to merge this, but I just wanted to confirm this with you first.

[Lokathor]

if that's on mac that's expected

[Cobrand]

@Lokathor Still on arch. I have a laptop with bumblebee so that might be an issue, regardless I ran the test both without and with optirun, and in both cases I got the panic.

[ghost]

I have the same problem on arch. Doesn't look like wgpu is able to figure out the graphics device, though that could be because this is some pretty old hardware.

[Cobrand]

Regardless, it's seems to be an upstream issue and wgpu is only a dev dependency for a specific example, so I think it's safe to merge. Even if it's an issue, no one is using it anyway (for now, since it's not even released), and they can always file an issue then.