Use OffscreenCanvas instead of `--proxy-to-worker`

[janpaul123]

I was trying to figure out how to get WORKERFS to work so I can read from File objects directly, and for that I needed my SDL application to run in a web worker. In order to do that I came across --proxy-to-worker, but ran into its limitations (e.g. it crashes on createVertexArray because getExtension('OES_vertex_array_object') is not implemented).

I was then wondering if --proxy-to-worker should be deprecated altogether, since we can now render to a WebGL OffscreenCanvas in a WebWorker directly. I'm still trying to figure out how to do this exactly, so maybe it's implemented already (-s PROXY_TO_PTHREAD?). In that case it might be good to update the documentation accordingly (and perhaps add a note to --proxy-to-worker that you shouldn't use it, and what the alternative is?). Thanks!!

[sbc100]

I think --proxy-to-worker (AKA PROXY_TO_WORKER) has largely been replaced by PROXY_TO_PTHREAD these days.

We do still have support for it though and there is still some testing. The last time this came up I think perhaps @juj still had some valid use cases for it?

[janpaul123]

Yeah, I spent some more time trying to figure out PROXY_TO_PTHREAD, and it looks like it hasn't been fully implemented for SDL yet, see e.g. emscripten-ports/SDL2#127 which is still open. So I don't think we can tell people to switch over from --proxy-to-worker quite yet.

It still might be worth adding a note in the docs at --proxy-to-worker, that PROXY_TO_PTHREAD might be preferable whenever possible, even if --proxy-to-worker doesn't get outright deprecated (if that's the direction things are going in). I'd be happy to make a little PR if people think this is a good idea.

[juj]

The last time this came up I think perhaps @juj still had some valid use cases for it?

I have actually never used --proxy-to-worker for anything. When I authored --proxy-to-pthread, I thought that would obsolete --proxy-to-worker, and on several occassions I have proposed for --proxy-to-worker to be removed, though @kripken has held on to it iiuc as he has dealt with users that have used --proxy-to-worker.

[kripken]

proxy-to-worker also does not require pthreads. It just proxies with postMessage basically, and it can proxy a single-threaded app, which can be useful.

(Perhaps when pthreads support on the web is ubiquitous that will not matter though.)

[stale]

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