Temporary key bindings using modes similar to i3/Sway

[maxigaz]

I would like to create key bindings that can be enabled and disabled on entering/leaving a special mode in a way that other bindings for the prefix and root key tables work while this special mode is being enabled.

Here's a typical workflow example I'm thinking of:

1. Map Ctrl+h/j/k/l to navigating between panes in a mode that is deactivated by default.
2. Enter this special mode by pressing prefix + R.
3. Do some work in Neovim and various shell prompts.
4. Leave the mode by pressing prefix + R again.

After some research, I tried to implement this using key tables. I added this to my .tmux.conf:

bind-key -T LAYOUT C-h select-pane -L    \; switch-client -T LAYOUT
bind-key -T LAYOUT C-j select-pane -D    \; switch-client -T LAYOUT
bind-key -T LAYOUT C-k select-pane -U    \; switch-client -T LAYOUT
bind-key -T LAYOUT C-l select-pane -R    \; switch-client -T LAYOUT

bind-key R switch-client -T LAYOUT             # Enter mode
bind-key -T LAYOUT C-bR switch-client -T root  # Return to normal (this probably doesn't work)

In this (incomplete) implementation, in tmux 3.5 (running with Alacritty and Arch Linux), while the LAYOUT table is active, as soon as I press a key that is not defined in this table, this table is deactivated, so the bindings for Ctrl+h/j/k/l are reset. Instead, I would like to keep these bindings on so everything else works as normal (and only Ctrl+h/j/k/l are overridden) as long as I press prefix + R to exit the mode. (It's possible to do this in i3 and Sway.)

As an alternative, I've managed to write a shell script that sets a user variable, and depending on its state, it manually creates and removes these bindings whenever this script is run:

#!/usr/bin/env bash
MODE=$(tmux show-option -qwv "@toggle-key-mode")

if [[ -z $MODE || $MODE == "off" ]]; then
  tmux bind-key -T root C-h select-pane -L
  tmux bind-key -T root C-j select-pane -D
  tmux bind-key -T root C-k select-pane -U
  tmux bind-key -T root C-l select-pane -R

  tmux set-option -qw "@toggle-key-mode" "on"
else
  tmux unbind-key -T root C-h
  tmux unbind-key -T root C-j
  tmux unbind-key -T root C-k
  tmux unbind-key -T root C-l

  tmux set-option -qw "@toggle-key-mode" "off"
fi

My question is, is this the best way to create these bindings? Or are key tables the way to go? Can the code snippet(s) above be improved?

[nicm]

what if you bind the any key in the table to switch back to the table?

[maxigaz]

I'm new to how key tables should be set up, so I may not fully understand how it works.

If your previous question was about what if I do this:

bind-key -T LAYOUT any switch-client -T LAYOUT

The result is that after I press prefix + R, I can switch panes with Ctrl + h/j/k/l, but then I'm basically stuck and can't do anything in Neovim anymore. (I can bring up the command prompt with : and then hit Esc, which takes me back to normal.)

Or am I misunderstanding you?

Edit: Sorry, I've just noticed your latest reply. I'm going to give it a try.
Edit 2: Oh, so you meant this, right?

bind-key -T LAYOUT any switch-client -T LAYOUT
bind-key R switch-client -T LAYOUT
bind-key -T LAYOUT R switch-client -T root

I can confirm that I can switch back to root with pressing R.

[nicm]

You need to give yourself a way to get back to the root table after you are done with the LAYOUT table.

[maxigaz]

Is it possible to have multiple key tables activated at the same time?

So, if I'm understanding it correctly, by default, only the root table is active. Can I enable both root and LAYOUT (LAYOUT overriding only the Ctrl + h/j/k/l keys from root) when I press prefix + r?

[nicm]

No, one key table at a time. To do what you want I think you could maybe try binding the Any key to send -K \; switchc -TLAYOUT (or maybe switchc -Troot \; send -K \; switchc -TLAYOUT) in LAYOUT, or you could make r swap the actual key bindings in root and forget about a second key table.

[maxigaz]

or maybe switchc -Troot \; send -K \; switchc -TLAYOUT

I tried bind-key -T LAYOUT any switchc -Troot \; send -K \; switchc -TLAYOUT. That made tmux completely unresponsive across all running sessions. (I had to kill the server through btop.)

or you could make r swap the actual key bindings in root and forget about a second key table.

OK, that sounds like the shell script I shared in my original post. I think I'll keep using that for now. (With bind R run-shell "/path/to/toggle-mode.sh".)

Thank you for your help!