GPURequestAdapterOptions.xrCompatible

[kainino0x]

We don't have a way to set GPURequestAdapterOptions.xrCompatible.

This probably should be a Wasm extension because it's not really meaningful outside the web. In the Web there's a known XR API (WebXR), but in native you could be interfacing with anything.

[kainino0x]

It's possible this should be integrated with compatibleSurface somehow though I'm not sure how.
In the web compatibleSurface can be ignored because all (non-xr) surfaces are compatible with all adapters.

[kainino0x]

Jan 23 meeting:

• Make it an WebXR-specific extension with boolean for now.
• Later maybe set it automatically when compatibleSurface is a WebXR surface.
• LK: Why do we have compatibleSurface?
  • It was added for wgpu:
    Pass Surface in AdapterDescriptor #39
    https://docs.rs/wgpu/latest/wgpu/type.RequestAdapterOptions.html#structfield.compatible_surface
    Unsure if it's used aside from WebGL.

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• Later maybe set it automatically when compatibleSurface is a WebXR surface.

I talked to @toji about this and he said in native you generally set up the graphics api first, then the xr api, so this would be backward.

[kainino0x]

As for actually using WebXR in Wasm (cc @toji), it looks like these are the libraries, though I don't know their implementation status.

• https://github.com/WonderlandEngine/emscripten-webxr
• https://docs.rs/web-sys/latest/web_sys/struct.Navigator.html#method.xr

library_webgpu (emdawnwebgpu) and wgpu would need to interop with these, respectively.
(The rust one obviously not being relevant to webgpu.h. Also I'd be unsurprised if it already interops.)