Support Ctrl Modifier for Word Navigation and Deletion in Text Areas

[iskandergaba]

PR Description

Unlike lazygit, most text editors and TUIs support Ctrl based key bindings for word navigation and deletion. They also support forward word deletion. As a heavy user of these key bindings, I wanted to extend their support to lazygit to switch between tools more easily.

I am sure that I am not the only one who would appreciate this, and in any case, this extension does not break any preexisting key bindings.

Changes:

• Ctrl+Left / Ctrl+Right: Move cursor one word left/right (alongside existing Alt+Left/Right and Emacs-style Alt+B/Alt+F)
• Ctrl+Backspace: delete word to the left (alongside existing Alt+Backspace and Ctrl+W)
• Ctrl+Delete / Alt+D: Delete word to the right (new; no equivalent existed before)

Note:

ModCtrl was previously disabled in gocui with a comment stating it didn't work with keyboard keys. This comment was written 5 years ago and mentions tcell.v1 while the project is currently using tcell.v2, so I suspect it is a bit legacy now, but I would like it if the maintainers double-checked that part. I managed to make ModCtrl work by patching tcell_driver.go to preserve it for right/left and deletion key events while keeping it stripped from all other ones, as before.

Please Check If the PR Fulfills these Requirements

• Cheatsheets are up-to-date (run go generate ./...)
• Code has been formatted (see here)
• Tests have been added/updated (see here for the integration test guide)
• Text is internationalized (see here)
• If a new UserConfig entry was added, make sure it can be hot-reloaded (see here)
• Docs have been updated if necessary
• You've read through your own file changes for silly mistakes etc.

[stefanhaller]

Thanks for the contribution. I'm not going to merge this because I'm in the process of rewriting the key handling in gocui and lazygit, so all the code you are touching here will be different. I will try to remember to make this change as part of that work.

However:

Unlike lazygit, most text editors and TUIs support Ctrl based key bindings for word navigation and deletion.

Which platform are you on? As far as I am aware, using Alt is standard on Mac. Windows does use Ctrl though; not sure about Linux, I don't have a Linux system to test this on.

I think I would like to avoid offering both variants on all platforms; I'd prefer to only have the one that is standard on each platform. Also, it would be good to make them configurable I guess.

Never seen Ctrl-Delete or Alt-D for forward-delete-word; is this standard? What software supports it?

[iskandergaba]

Thanks for the contribution. I'm not going to merge this because I'm in the process of rewriting the key handling in gocui and lazygit, so all the code you are touching here will be different. I will try to remember to make this change as part of that work.

Fair enough. Thanks for taking the time to consider the PR. I will lay out my case here.

I will start from this point and build back from there.

Never seen Ctrl-Delete or Alt-D for forward-delete-word; is this standard? What software supports it?

These shortcuts are standard on:

• Windows (on PowerShell, but not on CMD).
• bash shell:
  • Tested on Debian (Windows Subsystem for Linux)
  • Tested on Ubuntu (Gnome Terminal and Ghostty Terminal)

Here are a couple of sources that support the existence of the action and the key-binding (Alt+D):

• https://unix.stackexchange.com/a/461518
• https://www.gnu.org/software/bash/manual/bash.html#Killing-And-Yanking

Technically, the shortcut is the Emacs key-biding Meta-D, which maps to Alt-D usually. And since the default mode for bash is emacs (It can be switched to vi but who does that I guess?), you end up with that.

Which platform are you on? As far as I am aware, using Alt is standard on Mac. Windows does use Ctrl though; not sure about Linux, I don't have a Linux system to test this on.
Mainly GNU/Linux, bash specifically. Indeed, Windows uses Ctrl as well as almost all modern text editors.

For the sake of more clarity, I did some digging. Listing the key binding on a bash shell session using the bind command, we can find the following:

• Backward delete word:

$ bind -p | grep -w " backward-kill-word"
"\e\C-h": backward-kill-word
"\e\C-?": backward-kill-word
$ bind -p | grep -w " unix-word-rubout"
"\C-w": unix-word-rubout

• \e\C-h —> Alt+Backspace (terminals that send 0x08 for Backspace). Exists already.
• \e\C-? —> Alt+Backspace (terminals that send 0x7F for Backspace). Exists already.
• \C-w —>Ctrl+W Exists already.

Notes:

1. backward-kill-word and unix-word-rubout behave slightly differently. While unix-word-rubout stops at whitespaces only, backward-kill-word uses GNU Readline word definition and additionally stops at punctuation like /, . and -. But that's neither here nor there I guess.
2. The proposed Ctrl+Backspace default binding does not exist for this action, apparently, so this one is on me. It is however standard on PowerShell and most code editors, for what its worth.

• Forward delete word:

$ bind -p | grep -w " kill-word"
"\e[3;5~": kill-word
"\ed": kill-word

• \ed —> Alt+D (classic Emacs/Readline binding). Proposed.

• \e[3;5~ —> Ctrl+Del (the [3~ is the Del key, the 5 modifier means Ctrl). Proposed.

• Move one word backward:

$ bind -p | grep -w " backward-word"
"\e\e[D": backward-word
"\e[1;3D": backward-word
"\e[1;5D": backward-word
"\e[5D": backward-word
"\eb": backward-word

• \eb —> Alt+B (classic Emacs/Readline). Exists already.

• \e[1;3D —> Alt+Left. Exists already.

• \e[1;5D —> Ctrl+Left. Proposed.

• \e[5D —> Ctrl+Left (older terminal encoding). Proposed.

• \e\e[D —> Esc then Left.

• Move one word forward:

$ bind -p | grep -w " forward-word"
"\e\e[C": forward-word
"\e[1;3C": forward-word
"\e[1;5C": forward-word
"\e[5C": forward-word
"\ef": forward-word

• \ef —> Alt+F (classic Emacs/Readline). Exists already.
• \e[1;3C —> Alt+Right. Exists already.
• \e[1;5C —> Ctrl+Right. Proposed.
• \e[5C —> Ctrl+Right (older terminal encoding). Proposed.
• \e\e[C —> Esc then Right.

I think I would like to avoid offering both variants on all platforms; I'd prefer to only have the one that is standard on each platform. Also, it would be good to make them configurable I guess.

Fair point. Ultimately, this has to do more with the shell you use rather than then the OS. The reason you can't find those key bindings on macOS is because it defaults to zsh rather than bash. zsh uses ZLE (Zsh Line Editor), not GNU Readline, leading to some different key bindings, even though the emacs-style ones remain the same (Ctrl+A, Ctrl+E, Alt+B, Alt+F, etc.).

I guess I just wanted less friction switching between my code editors and Lazygit. I think it can be configurable, say bash-style, zsh-style, and PowerShell-style key bindings. An auto setting could select the key binding corresponding to default shell, with a fallback to bash for Linux, zsh for macOS, and powershell for Windows should the shell session not match any style.

Or you could force the law on everyone and dictate the key bindings :)

Either way, I hope this discussion has shed more light on the matter and that it will help your technical choices in the ongoing rewrite. Good luck.

[codacy-production]

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