chat VS notcurses

TUIs over ssh/telnet can be a lot of fun. Especially in cases where multiple people can interact with each other on the server. It simplifies the programming model as you only have one state on the backend that you render to multiple connections. Syncing up everyone becomes trivial. You can also use some React concepts, like rendering a virtual TUI and sending just the right set of minimal escape sequences back to the user to bring their display up to date.

A few months ago I implemented a telnet chat server[0] for fun and it was surprisingly easy to do so. Even by using a wasm vm that I was still working on at the same time.

[0]: https://github.com/lunatic-solutions/chat

We are investing a lot of effort into making Lunatic feel native to the particular language and ecosystem. If you look at the Rust chat server we built in Lunatic (https://github.com/lunatic-solutions/chat), it fully integrates with cargo. You just run your typical “cargo run” command, it will compile the app to wasm and use lunatic to run it. If you want to run your test, you can just do “cargo test”.

wasm-bindgen is necessary only because it’s really hard right now to merge the wasm world and the JS one in the browser. We have the advantage here of staying out of the browser.

It took me around a week to build it with Rust + Lunatic and you can check out the code here. If you would like to try it out you can connect to it with:

Recently I implemented a command line chat server in Rust using an actor framework. I model each TCP connection as an actor.

Hi HN,

I'm working on an Erlang inspired WebAssembly runtime for the backend[0]. Recently I added TCP support and was looking for apps I could build with it. I ended up building a telnet line chat app. It was a great dogfooding experience and has a nice retro feel to it.

You can access the US server with:

> telnet lunatic.chat

or the EU one with:

> telnet eu.lunatic.chat

Pick the one closer to you, as all the rendering is done on the backend and lower latency will mean better UX.

The server is open source[1] and written in Rust. The Rust code is then compiled to WebAssembly and runs on top of Lunatic. Each connection runs in a separate (lightweight) process, has it's own state and sends just a diff of esc-sequences back to the terminal to bring it up to date with the current render buffer. Everything is deployed to an ARM Linux box.

[0]: https://github.com/lunatic-solutions/lunatic

[1]: https://github.com/lunatic-solutions/chat

The server is open source and written in Rust. The Rust code is then compiled to WebAssembly and runs on top of Lunatic. Each connection runs in a separate (lightweight) process, has it's own state and sends just a diff of esc-sequences back to the terminal to bring it up to date with the current render buffer. Everything is deployed to an ARM Linux box.

> The only reason we don't have animation frameworks for the terminal is because it's not possible

https://nick-black.com/dankwiki/index.php/Notcurses

Notcurses. Install it and run notcurses-demo to be suitably impressed.

Same for me, I would be much more motivated if there was something like textual for Rust. Given the capability of terminal emulators now I think Rust is lacking behind in the TUI field. Just checkout what can be done with something like notcurses

On the application side of rendering, see notcurses, it is at the leading edge: https://github.com/dankamongmen/notcurses

Other TUI libraries of note: https://github.com/dankamongmen/notcurses/blob/master/doc/OT...

The broader world probably knows him best for the terminal handling library Notcurses[1] and a lot of telling terminal emulator authors to get their shit together.

I’ve had his grad-school project libtorque[2] (HotPar ’10), an event-handling and scheduling library, on my to-read list for years, but I can’t seem to figure out how it accomplishes the interesting things it does.

[1] https://nick-black.com/dankwiki/index.php/Notcurses, https://github.com/dankamongmen/notcurses/

[2] https://nick-black.com/dankwiki/index.php/Libtorque

In XTerm, this (rightly) makes no difference. In Foot and Contour however, you still end up a line resp. a screen below where you started, if now with the correct horizontal position.

So it seems to me like what you want should work by default, except it doesn’t.

It should be possible to instead just treat the whole thing as a graphical overlay (by computing or directly asking for the character cell size, as Kirill Panov rightly admonishes me is possible with XTWINOPS) without touching the cursor; that’s what the “sixel scrolling” setting (DECSDM) is supposed to do. Then you can just manually move the cursor forward however many positions after you’re done drawing.

Except apparently the DEC manual (the VT330/340 one above) and DEC hardware contradict each other as to which setting of DECSDM (set or reset) corresponds to which scrolling state (enabled or disabled), and XTerm has implemented it according to the manual not the VT3xx[1,2,3]—then most other emulators followed suit[4]—then XTerm switched to following the hardware[5,6] (unless you and that’s what I’m seeing on my machine right now. So now you need to check if you’re on XTerm ≥ 369 or not[7]. If I’m reading the Notcurses code right, other terminals have followed suit[8].

Again, ouch.

P.S. It seems DEC had an internal doc for how their terminals should operate (DEC STD 070) [9]. It does not document DECSDM at all.

[1] https://github.com/wez/wezterm/issues/217#issuecomment-86449...

[2] https://github.com/hackerb9/lsix/issues/41

[3] https://github.com/dankamongmen/notcurses/issues/1782

[4] https://github.com/arakiken/mlterm/pull/23

[5] https://invisible-island.net/xterm/xterm.log.html#xterm_369

[6] https://invisible-island.net/xterm/ctlseqs/ctlseqs.html#h3-T...

[7] https://github.com/dankamongmen/notcurses/commit/0918fa251e2... (the correct version cutoff is 369 not 359, the patch contains a now-fixed bug)

[8] https://github.com/dankamongmen/notcurses/blob/master/src/li... (look for mentions of invertsixel)

[9] http://www.bitsavers.org/pdf/dec/standards/EL-SM070-00_DEC_S...

And there's also the notcurses library: