Web backend crashes when initialized within a worker

[strax]

Description
The web backend uses web_sys::window to obtain a handle to the global Navigator object. This does not work when called from a worker scope since there is no window global variable nor a Window interface.

Repro steps
Create a Worker that executes a Rust program compiled to WebAssembly calling wgpu::Instance::new. Unfortunately I don't have a minimal repro available at the moment.

Expected vs observed behavior
Observed behavior: the web backend tries to obtain a handle to the window object and performs an instanceof check against the Window interface, which does not exist in the worker scope. This results in an error:

Uncaught (in promise) ReferenceError: Window is not defined

Expected behavior:
In a worker scope, a web_sys::WorkerGlobalScope could be used instead to obtain the Navigator handle, but this might be tricky in practice (rustwasm/wasm-bindgen#1046). Since the program will crash and not return None when window is not available, it is not enough to use Option::or to fall back to, say, web_sys::global(). Based on rustwasm/wasm-bindgen#1982 (comment), this is a problem with other web_sys consumers too and might require some glue code like this.

Platform

• wgpu version: master

[codeart1st]

Can confirm this for me. Tried an experiment with OffscreenCanvas and run into the same problem.

Current solution for me in my worker.js is this hack:

self.Window = WorkerGlobalScope
self.window = self
self.window.document = {
  querySelectorAll: () => {
    return [canvas]
  }
}

Not great, but do the job. canvas is the transfered OffscreenCanvas instance.

Edit: #1932 create_surface_from_offscreen_canvas. So only the first line of the "hack" needs to be used.

[teoxoy]

I believe this was fixed by #2858, closing.

[codeart1st]

self.Window = WorkerGlobalScope is still needed for me.

Edit: Stack trace indicated that I was on my wrong branch without the updated wgpu dependency.
Edit: Tried it again on the correct branch and it works without any workarounds now. 👍