wgpuInstanceCreateSurface fails because document is undefined

[Ravbug]

I am trying to create a Surface from an HTML element:

WGPUSurfaceDescriptorFromCanvasHTMLSelector canvasDesc{
    .chain = {
        .next = nullptr,
        .sType = WGPUSType_SurfaceDescriptorFromCanvasHTMLSelector 
    },
    .selector = "#canvas"
};
WGPUSurfaceDescriptor desc{
    .nextInChain = &canvasDesc.chain,
    .label = "Surface"
};
surface = wgpuInstanceCreateSurface(instance, &desc);

However, this call fails because in calling findCanvasEventTarget it calls findEventTarget, where document is undefined and so returns undefined.

// domElement evaluates to undefined
var domElement = specialHTMLTargets[target] || (typeof document != 'undefined' ? document.querySelector(target) : undefined);

Stack trace and output:

Version of emscripten/emsdk:

emcc (Emscripten gcc/clang-like replacement + linker emulating GNU ld) 3.1.45 (ef3e4e3b044de98e1811546e0bc605c65d3412f4)
clang version 18.0.0 (https://github.com/llvm/llvm-project d1e685df45dc5944b43d2547d0138cd4a3ee4efe)
Target: wasm32-unknown-emscripten
Thread model: posix
InstalledDir: C:\Users\Admin\Documents\emsdk\upstream\bin 

Browser version:
Chromium Version 118.0.5987.0 (Developer Build) (64-bit)

[sbc100]

It looks like you are maybe trying to use webgpu from a worker thread? is that correct? Are you starting the application in a worker, or are you attempting to use this API from a pthread perhaps?

[Ravbug]

I'm not using a worker thread, but I am using asyncify. Could that also cause issues?

[sbc100]

If you are not using a worker then how could document not be defined. IIUC its always defined on the main thread.

[Ravbug]

I am not manually creating any worker threads, but I am also using PROXY_TO_PTHREAD. If I remove all pthread-related compile and link flags, then the error does not occur. Is this meant to work with PROXY_TO_PTHREAD?

[sbc100]

I have change that proxies the webgpu calls back to the main thread: #20124. Hopefully once this change lands it will fix your problem.