Key binding questions around making a complete Vim-like interface

[whiteinge]

Hello. I've been playing with mle on and off for a few days and I just love the simplicity of the code and the minimal philosophy of leaning on external tools as much as possible. I'm an old Vim user so I've started hacking around a .mlerc with an eye toward how Vim-like I can make it (ala Emacs and Evil) and I was hoping you could field a few questions around what's possible and what you'd be interested in adding or not.

General questions:

• Is it possible to bind the escape key? -kcmd_pop_kmap,escape, doesn't seem to work.
• Can kdef/kbind be done from Lua? I spent some time poking through the source, my C knowledge is limited, but it looks like not. Is that something you'd be interested to add? Asking because it would be nice to put everything in one -x mlevil.lua file. :-)
• Would you be interested to enable the wiki on this repo so people can share tips, configs, and lua scripts?

Vim-specific questions:

• What are your thoughts on multiple commands in one mapping? E.g., Vim's A to append to the end of a line.

  • Possible API: -k"cmd_move_eol;cmd_push_kmap,kmap_insert",A,

• Thoughts on multiple key presses for one command? E.g., Vim's gg.

  • Possible API - notice overlapping kbinds and wait for another keypress: -kcmd_move_beginning,gg,

  • Better(?) possible API - use modes and then push and pop modes via the above 'multiple commands in one mapping' API:

    -kcmd_push_kmap,g,kmap_g
    -Kkmap_g,,0
    -k"cmd_move_beginning;cmd_pop_kmap",g,

I understand if the above is beyond the scope of your project but I'm excited about it and at least wanted to raise the questions. Thanks for your time!

[adsr]

Hello @whiteinge, glad to hear you like it.

Is it possible to bind the escape key? -kcmd_pop_kmap,escape, doesn't seem to work.

Not currently. mle uses termbox which supports two input modes, TB_INPUT_ESC which emits escape inputs but sacrifices meta inputs (alt+...), and TB_INPUT_ALT which is the opposite. mle hardcodes TB_INPUT_ALT. It would be nice if there was a third mode that would emit escape inputs if there is nothing left in the input buffer.

https://github.com/termbox/termbox/blob/8dc56647b963768cec4e8b0ff1350055d54fc9e3/termbox.c#L650

I think (inputmode & TB_INPUT_ESC || len == 1) would handle this in the nominal case. I'm sure there are edge cases with slow inputs or large / full buffers. It is a good feature request.

Would you be interested to enable the wiki on this repo so people can share tips, configs, and lua scripts?

Sure, I'll enable it.

Can kdef/kbind be done from Lua? I spent some time poking through the source, my C knowledge is limited, but it looks like not. Is that something you'd be interested to add? Asking because it would be nice to put everything in one -x mlevil.lua file. :-) Vim-specific questions: ...

Binding keys from Lua is not supported but it is easy to add. A long while ago I was working on built-in basic vim support https://github.com/adsr/mle/blob/6a7f9c10083c0c48046688cf403aa9a6bb6c8973/cmd_vim.c I removed it because I'm a pretty basic vim user and realized I was not a good judge of how accurate the emulation was. Let me know if you'd like to collaborate on resurrecting it.

[whiteinge]

Thanks for the replies. I'll play with TB_INPUT_ESC this weekend to see how it feels.

I am interested to collaborate on Vim support! Although I'm not sold on baking it directly into mle via C for a few reasons:

• It will bloat mle. The bulk of Evil clocks in at 541 lines of mappings and configuration and while that is pretty reasonable, a huge part of the appeal of mle (for me and a couple mle mentions around the Suckless community that I've noticed) is that it hovers around the ~10k LOC mark which is amazing and tiny for a capable editor. Pushing Vim compat off to an mlerc or Lua inclusion will (mostly) separate the editor from the keybindings.

• Your push/pop kmap idea is really compelling. Although I've only played with making a Vim-like environment for a couple hours yet, it already comes so close to enabling that -- and all in user-space. I think a couple tweaks could get us the rest of the way there. I'd be happy to flesh out a more detailed Evil/mle-cmd comparison to vet that idea more thoroughly if you'd like.

• mle isn't Vim. Vim-like feature set will necessarily have to be Good Enough (TM) and there will inevitably be concessions and features that don't make sense to implement (encryption, rot13, some window management, etc). Some of those will be opinions that invite disagreement or debate and allowing users to easily roll their own via an mlerc could be a great way to deflect differing opinions.

• Not just Vim. If it's possible to implement a Vim-like environment in user space then it should also be possible to make other environments as well such as Emacs-style key chords or things like Kakoune (it switches Vim's verb -> object approach with object -> verb which might jive quite well with mle's cursors, selections, & anchors).

Thoughts, rebuttals, counterpoints very welcome.

[hovsater]

[...] Let me know if you'd like to collaborate on resurrecting it.

Just want to chime in here and say it's be happy to help out wherever I can. 🙂

[adsr]

Good points @whiteinge. I tend to agree overall.

The bulk of Evil clocks in at 541 lines

Impressive. Very curious to see it. I didn't realize you were already working on one.

Thoughts on multiple key presses for one command? E.g., Vim's gg. Possible API - notice overlapping kbinds and wait for another keypress: -kcmd_move_beginning,gg,

By the way, this should already be supported, e.g.:

mle -K kmap,,1 -k 'cmd_move_beginning,g g,' -k 'cmd_move_end,g G,' -n kmap

Maybe that helps you.

What are your thoughts on multiple commands in one mapping?

Interesting idea. I agree the current kbinding format is limiting. It would be nice if commands were more composable. There used to be an 'editing language' feature that attempted to address this: https://github.com/adsr/mle/blob/adf11c6f266fcb7f41ef395662fc50c271c25461/README.lel.md The idea was you could write a tiny program to do a more complex action and kbind it as usual. It was cool but I never used it and also overlapped with user scripts. But the idea of being able to express a little bit of logic inside a kbinding is still appealing to me.

For kmaps, I imagine it'd help if they had callbacks and/or some sort of internal state. Might help in implementing things like Vim's undo in normal mode or visual mode.

[whiteinge]

I didn't realize you were already working on one.

A little, yeah. I started porting this file from the Evil project over to mle to see how far I could get with push/pop kmaps. That file is 541 lines, my port is just 35 lines so far. You can view it here and I'd like to move it into the wiki once it's farther along. There's a few things that I think are possible with mle as-is (such as chording like cw to change word) that I haven't gotten to yet; there's a few things that probably aren't possible yet; and there's a few things that aren't applicable to mle (tabs, windows). I haven't tried yet but I was hoping to get some :ex-like behavior from mle_prompt_input and Lua.

That file is only part of what makes Evil Vim-like but it's a substantial part. There's also a nice similarity between Emacs command names and mle command names.

By the way, this should already be supported [...] Maybe that helps you.

Oh! Space-separated keys. Yes that helps, thanks.

Is it possible to map the two mle commands that accept ** arguments?

echo '-kcmd_move_until_forward,f,**'
echo '-kcmd_move_until_back,F,**'

For kmaps, I imagine it'd help if they had callbacks and/or some sort of internal state. Might help in implementing things like Vim's undo in normal mode or visual mode.

This is a good example of where I think trying to emulate Vim too much (or too early) could potentially send mle down a bloat-y path. -k 'cmd_undo,u,' doesn't work like Vim's undo but I think that's ok -- and it's particularly ok as a first-pass for Vim-like. IMO, it would be a bigger initial impact to get things like counts, movements, chording, and text objects as close as possible. There will inevitably be mle-isms (multiple cursors, save dialogs, copy & paste semantics) that will differ from Vim and I think that's probably ok forever, but certainly ok for now.

[adsr]

Excellent! Please let me know when it gets to a steady state. I'd like to add a link to it in the readme at least if that is ok by you.

Is it possible to map the two mle commands that accept ** arguments?

Yes, what you have should work (with space-separated keys):

echo '-kcmd_move_until_forward,f **'
echo '-kcmd_move_until_back,F **'

Fully agree re: avoiding bloat. I've wanted to rewrite the kmap code for a long while because it's hard to follow. I'd only consider the rewrite successful if the code ended up simpler. Bonus if the features are more flexible.

[adsr]

Feel free to re-open