How to use ratatui with an "emulated PTY"? Eg serving over an SSH server?

[samuela]

Hi folks! 👋 I'm curious if ratatui support rendering to an "emulated PTY", eg. a PTY handled by an SSH server. I'm working on building a custom SSH server with russh that serves a TUI application over the connection. In an ideal world I'd like to be able to use hook everything together in-process such that ratatui renders to an SSH client's PTY.

Can ratatui handle such a usecase? What would be the best way to go about it?

[joshka]

This is probably something that would be implemented upstream in Crossterm, Termion (both of which support constructing a backend passing in anything that implements the std::io::Write trait), or termwiz (which works similarly under the hood).

There is example code for termion in the russh repo https://github.com/search?q=repo%3Awarp-tech%2Frussh+termion&type=code, but it looks like it's just the client side not the server side. It might be worth asking over on russh about Crossterm / Termion on the server side of things.

Alternatively if that approach doesn't work out you could write a backend that implements ratatui::backend:: Backend over the rushh stuff. That would be pretty neat but more work perhaps. Taking a quick look at russh it looks like everything is async, which may introduce an extra level of difficulty if you're not adept in the ways of Futures and Streams.

I look forward to seeing what you come up with.

[Eugeny]

Heya, russh maintainer here. Having a pluggable backend is the ideal solution here, but something is amiss in crossterm's implementation since it only seems to accept a pluggable Write output - but what about stdin/SIGWINCH/termios? All these are tunnelled over the SSH protocol.

ratatui::Backend is definitely doable but requires basically rewriting crossterm's Linux implementation yourself

Just as I was writing this I realized that ratatui doesn't provide input handling, hence there's nothing to implement here. 🤦
@samuela you can basically just use a CrosstermBackend::new(channel.into_stream()) for the output part. I don't know what crate you're using to handle user input, but you should look into whether that crate supports receiving events programmatically instead from the stdin's PTY.

[joshka]

Yeah, we just do the buffer -> backend part, the app handles the user input / app loop part.

[alexandrebrg]

Quick update on this discussion as russh maintainers recently created an example app with ratatui here :)

[ricott1]

Hi, I am the author of the linked example. I have an example app using this approach here: https://github.com/ricott1/sshattrick

[joshka]

I also just created a simple example of a Pong game
SSHattrick is pretty awesome btw.