uv_backend_fd like support to make integration to OS gui event loop possible!

[congzhangzh]

I want to make webview_deno support async binding, which under the hood need pool tokio event in separate thread, and trigger on UI thread!

Is your feature request related to a problem? Please describe.
no

Describe the solution you'd like
A backend fd mechanism

Describe alternatives you've considered
no

Additional context
No

webview/webview_deno#185 (comment)
https://docs.libuv.org/en/v1.x/loop.html#c.uv_backend_fd
https://www.electronjs.org/blog/electron-internals-node-integration
webview/webview#578
webview/webview_deno#185

[Darksonn]

It's unclear exactly what you're asking for, but it sounds like a duplicate of #6178.

[congzhangzh]

Hi folks, I want do something like integrate event loop with OS gui event loop, and electron already find a way to do it, which need pool event loop in backend thread and post and run on ui thread.

refs:

https://docs.libuv.org/en/v1.x/loop.html#c.uv_backend_fd
https://docs.libuv.org/en/v1.x/loop.html#c.uv_run_mode
https://github.com/electron/electron/blob/8f00cc9c0e78b95e4de14b9b9e1a7df20935e948/shell/common/node_bindings.cc#L929
https://gist.github.com/bagder/ffb613e3c3c5f41813b31fc09ef1c261
https://docs.libuv.org/en/stable/guide/eventloops.html

tks:)

[Noah-Kennedy]

I'm working on a patchset right now which will expose functionality which I believe will resolve this.

[pbk20191]

@Noah-Kennedy glad to here that, I have one question. Will this also expose iocp for windows? Which makes it possible to merge MessageQueue and IOCP loop using MsgWaitForMultipleObjects.

If it could I want tokio to expose iocp unlike libuv which does not return valid handle from uv_backend_fd

[congzhangzh]

@Noah-Kennedy Hi Noah, maybe Tokio can expose four high-level functions to make this process easy to work like Python, I add Python a asyncio guest mode to make Python asyncio stdlib easy to work with any GUI framework & eventloop :)

tokio will run on backend thread, all the real work starts & callback itself will happen on UI or third-party eventloop.

Btw, this will make deno base electronjs like framework easy to do:)
denoland/deno#3234
https://electronjs.org/blog/electron-internals-node-integration
webview/webview_deno#185

poll_events # poll io event, this will be done in the guest mode backend thread
process_events # process it, this will be run on UI thread
process_ready # process coroutine, this will be run on UI thread.
run_coroutine_threadsafe # run on UI thread, wake up tokio thread, coroutine will be something like UI call back

https://github.com/congzhangzh/asyncio-guest/blob/master/asyncio_guest/patches/base_events.diff
https://github.com/congzhangzh/asyncio-guest/blob/016730a23d991105bef0728de3e297ea74ecafb2/asyncio_guest/asyncio_guest_run.py#L7