Escape sequence to report operating system

[krobelus]

Is your feature request related to a problem? Please describe.

I want to add platform-native default key bindings to fish shell.
For example if the terminal is running on macOS, alt-backspace should delete the last word and on other platforms ctrl-backspace should do that.
I believe this should be based on the client system the terminal is running on.
For example, when I run kitty -e ssh some-linux-host fish on macOS, the shell should be able to detect that.

Describe the solution you'd like

If it doesn't already exist, maybe something similar to XTVERSION but printing the operating system name from uname.

$ printf '\x1b[>1q'; cat -v
^[P>|Linux^[\

Could also make the request encoding include uname or OS, to make it obvious. That would probably require using a different command type. Happy to look at some alternatives tomorrow.

Describe alternatives you've considered

fish could map both alt-backspace and ctrl-backspace to the same thing.
That's not ideal because we want the other key to do something else (delete an entire shell-quoted argument).

[krobelus]

Thanks that works great since fish already uses XTGETTCAP for querying other capabilities.
Unfortunately at least the conhost terminal breaks on such DCS sequences (it echoes them),
so it looks like they need to limit usage of this feature to known-gnood terminals until they find a hack
(for example one could detect whether the terminal is broken in this way,
or perhaps send a hex-encoded version of DCS sequences as OSC and have the terminal interpreted that.. just an idea)
Unfortunately I'm not aware of a way to get a terminal's unique fingerprint so I don't even know how to work around specific bad terminals (that don't implement XTVERSION)

[kovidgoyal]

Yeah there is no universal terminal fingerprint escape code. There are technically the Device Attributes primary, secondary and tertiary but terminals just spoof those as compat hacks.

[krobelus]

Happily we found a workaround: 1. begin synchronized update, enable alternate screen 2. write some DCS commands 3. disable alternate screen, end synchronized update 4. [wait for DCS replies] What a relief. We can query for features without terminfo now, what a time to be alive.

[kovidgoyal]

nice trick!