3 ms·

Hardcoding an escape sequence or two because you’re using an as-of-yet immature language environment with cumbersome and/or inadequate, or even buggy, libraries

• hnlmorg 2y ago
  > Personally, I would have the program run tput(1) as a subprocess and capture (and save) the correct escape sequences from the pipe, for later re-use, but I could imagine how, in some special cases, that might not be practical. That's not a bad suggestion generally speaking. I've seen a fair amount of shell scripts that do this too. In this specific case, they're running DNS lookups in parallel to speed the tool up, so I think forking tput wouldn't be preferable. But for tools that are more forgiving for latency (and specifically targeting POSIX too), that's definitely an option. > You originally wrote “in reality you can get away with hardcoding vt100 sequences for most things.” But now you want to argue that you were always talking only about this specific use case? Fair point. > (Also, it seems that for this specific use case, only one escape sequence would be needed: “cursor_up”/“cuu1”.) I was thinking cursor down too, but actually you're right, \n would do that job better for a multitude of reasons. Edit: thinking about this more, there’s a reverse carriage return ASCII character so you don’t actually need any ANSI escape sequences at all. > The same was said about the x86 instruction set, and it did look completely entrenched for many years. But then it wasn’t. And old ideas and concepts about what can be done with terminals, like MGR, may yet rise again. I see things like sixels only as symptoms of a pent-up demand for this. And people won’t want to go through ANSI X3.64 sequences to render their remote applications, so non-ANSI terminal protocols are likely to emerge again. Professionally speaking: I can't see that happening. More systems are implementing vt100 support, not less. And escape sequences are "easy" to implement and "good enough" that most people have a quick moan about them but then quickly move on to getting whatever job they want done, done. Plus the decline of x86 was driven by $$$ (like most changes in IT). Apple wanting to own more of the pipeline. Datacentres wanting to reduce infrastructure and operational costs. And ARM was already as old and established as x86 so it wasn't like trying to create a new standard (how many other architectures have fallen by the wayside?). There isn't anything like that happening for terminals right now. However, personally speaking: I genuinely hope you're right. The status quo sucks. Just so long as whatever new that comes along is a complete redesign. In-band meta sequences are just horrible. But I think realistically, those that don't like the status quo with terminals either use web technologies or Microsoft RPCs instead. And those that like the terminal have already learned to live with its many warts.
  • teddyh 2y ago
    Just like UTF-8 unified ASCII with extended character sets, maybe ANSI X3.64 can be unified with something more, incorporating features from MGR and/or sixels. > there’s a reverse carriage return ASCII character Which one? And if it works, why does ”tput cuu1” not output it, instead of ^[M or ^[[A?
    • hnlmorg 2y ago
      > Just like UTF-8 unified ASCII with extended character sets, maybe ANSI X3.64 can be unified with something more, incorporating features from MGR and/or sixels. Not another character set please. Terminals are better off UTF8 and we are better off keeping control sequences out of character sets. It made sense in the 60s and 70s but makes zero sense these days. Plus Unicode has enough footguns as it is without introducing control sequences. In my opinion the only good way to advance beyond escape sequences is to do away entirely with in-band control codes. Control codes should be on a separate channel. This is basically the only thing HTML gets right: separating content from formatting and control sequences. Having that separation in the terminal would also allow for less hacks in pipe detection. To elaborate, `isatty()`, the C function that's used to detect if a fd is a pipe or TTY, basically just performs a terminal-specific I/O control operation to see if the file descriptor can handle terminal-specific controls, and if it can't, then assumes the fd is not a TTY. Its a complete hack in my opinion. A hack that works and has worked for a great many years. But a hack non-the-less. Also having a separate data and control channel allows you to incorporate more meta data about the data channel. I actually use this trick in my $SHELL, Murex [0]. It's a typed shell (like Powershell but far less verbose and far more ergonomic to use) however it works perfectly fine with standard POSIX pipes because the type annotations are sent over a different channel. So you have the best of both worlds: raw byte streams for anything classical, but also rich type metadata for anything that understands Murex pipes. While introducing zero boilerplate code for anyone who uses the shell. > > there’s a reverse carriage return ASCII character Which one? And if it works, why does ”tput cuu1” not output it, instead of ^[M or ^[[A? You're right. I was thinking of ^[M [1] (C1 control sequence) and getting confused with C0 sequences (ie ASCII characters). Wasn't helped by me misremembering that modern terminal emulators tend to treat multiple different ASCII characters as LF, such as VT (vertical tab) and FF (form feed) [2] [0] https://murex.rocks https://murex.rocks [1] https://github.com/lmorg/mxtty/blob/main/virtualterm/ansi_c1.go#L198 https://github.com/lmorg/mxtty/blob/main/virtualterm/ansi_c1... [2] https://github.com/lmorg/mxtty/blob/main/virtualterm/ansi_c0.go#L51 https://github.com/lmorg/mxtty/blob/main/virtualterm/ansi_c0...