shift-space produces escape sequence in terminal

[smolin]

Steps to reproduce

1. start macvim gui
2. enter :term<enter> to start terminal mode
3. enter od -c<enter> to start octal dump
4. enter -space followed by followed by -D to end input
5. observe output

   % od -c
   ^[[32;2u
   0000000 033   [   3   2   ;   2   u  \n
   0000010

Expected behaviour

 I expect shift-space to produce a space character, 020

% od -t x1

0000000 20 0a
0000002

Version of Vim

VIM - Vi IMproved 8.2 (2019 Dec 12, compiled Sep 24 2021 14:13:28) Included patches: 1-3455

Environment

OS: MacOS 10.15.7 and 12.0.1 terminal: MacVim 8.2.3455 TERM: xterm shell: GNU bash, version 5.1.12(1)-release (x86_64-apple-darwin21.1.0)

FWIW I tried a vanilla env without .bashrc .bash_profile and .vimrc with same result

Logs and stack traces

No response

[eirnym]

@smolin thank you. for an issue

Could you please to try this in Vim in terminal (with no GUI) and vanilla vim, like /usr/bin/vim?

[smolin]

@eirnym Thanks for getting back to me. I tested just now with /usr/bin/vim and /Applications/MacVim.app/Contents/MacOS/Vim and both result in the expected behavior - results in char 020 AKA

Thanks! I love MacVim by the way, otherwise it's the bee's knees.

[mplough]

See also https://github.com/vim/vim/issues/6040.

@smolin - this issue is fascinating and it definitely nerd sniped me. It's easily reproducible but I don't have enough arcane knowledge about terminal emulators to be totally sure that it's a bug in MacVim or even in Vim for that matter.

With iTerm 2 it's possible to make the issue happen or not happen at will with just /usr/bin/vim. By default, Shift+Space in a :term terminal results in a space being inserted. However, with Report modifiers using CSI u enabled, Shift+Space in a bash prompt in a :term terminal gives a ^[[32;2u. It also results in a ^[[32;2u in the regular shell with no vim involved at all.

The Fish shell (which doesn't use readline) supports CSI u as well; see this example of binding Shift-Space. Running that bind at a fish prompt inside a :term terminal results in a regular space character being inserted.

The Bash shell does not currently support CSI u as a result of its use of readline. From the second email on this thread from 18 April 2022 on the bug-readline list, support for CSI u isn't currently a priority:

I think I'll wait until more terminal emulators support this.

Vim appears to be sending reasonable CSI u codes to its subprocesses, though I can't find any explicit mention of CSI u support in https://github.com/vim/vim discussions.

From https://github.com/vim/vim/issues/6040#issuecomment-827176487:

As a workaround you can remap Shift-Space:

tnoremap <S-space> <space>

This mapping will break apps that expect to receive Shift-Space!

For example, the Shift+Space mapping that works in vim inside a vim terminal won't work.

Hope this helps clarify things even if it doesn't fix the issue. This might go away entirely as more applications start supporting CSI u.

[eirnym]

As it's Vim core issue, it's better to discuss it there and when comment here when it's resolved

[eirnym]

Thank you @mplough for linking the base issue