Simple Vi mode with Karabiner-elements and Hammerspoon

init.lua

local module = {}

module.debugging = false -- whether to print status updates

local eventtap = require "hs.eventtap"
local event    = eventtap.event
local inspect  = require "hs.inspect"

local keyHandler = function(e)
    local watchFor = {
            h = "left",
            j = "down",
            k = "up",
            l = "right",
            u = "delete",
            i = "forwarddelete"
        }
    local actualKey = e:getCharacters(true)
    local replacement = watchFor[actualKey:lower()]
    if replacement then
        local isDown = e:getType() == event.types.keyDown
        local flags  = {}
        for k, v in pairs(e:getFlags()) do
            if v and k ~= "fn" then -- fn will be down because that's our "wrapper", so ignore it
                table.insert(flags, k)
            end
        end
        if module.debugging then print("viKeys: " .. replacement, inspect(flags), isDown) end
        local replacementEvent = event.newKeyEvent(flags, replacement, isDown)
        if isDown then
            -- allow for auto-repeat
            replacementEvent:setProperty(event.properties.keyboardEventAutorepeat, e:getProperty(event.properties.keyboardEventAutorepeat))
        end
        return true, { replacementEvent }
    else
        return false -- do nothing to the event, just pass it along
    end
end

local modifierHandler = function(e)
    local flags = e:getFlags()
    local onlyControlPressed = false
    for k, v in pairs(flags) do
        onlyControlPressed = v and k == "fn"
        if not onlyControlPressed then break end
    end
    -- you must tap and hold fn by itself to turn this on
    if onlyControlPressed and not module.keyListener then
        if module.debugging then print("viKeys: keyhandler on") end
        module.keyListener = eventtap.new({ event.types.keyDown, event.types.keyUp }, keyHandler):start()
    -- however, adding additional modifiers afterwards is ok... its only when fn isn't down that we switch back off
    elseif not flags.fn and module.keyListener then
        if module.debugging then print("viKeys: keyhandler off") end
        module.keyListener:stop()
        module.keyListener = nil
    end
    return false
end

module.modifierListener = eventtap.new({ event.types.flagsChanged }, modifierHandler)

module.start = function()
    module.modifierListener:start()
end

module.stop = function()
    if module.keyListener then
        module.keyListener:stop()
        module.keyListener = nil
    end
    module.modifierListener:stop()
end

module.start() -- autostart

return module

karabiner.json

{
    "profiles": [{
        "devices": [],
        "name": "Default profile",
        "selected": true,
        "simple_modifications": {
            "caps_lock": "fn"
        },
        "standalone_keys": {
            "caps_lock": "caps_lock"
        },
        "one_to_many_mappings": {},
        "virtual_hid_keyboard": {
            "caps_lock_delay_milliseconds": 0,
            "keyboard_type": "ansi",
            "standalone_keys_delay_milliseconds": 100
        }
    }]
}

This is a configuration for Karabiner-elements and Hammerspoon to bring back Simple Vi mode from old Karabiner

What it does:
First it maps caps_lock to fn when you press and hold, and keeps caps_lock functionality if you press and release quick, all this in karabiner.json file

Then with the help of Hammerspoon, in init.lua we map:
fn + hjkl to arrows
fn + u to delete
fn + i to forward_delete

Hope it helps!!

You can easily modify the bindings to your taste or to add more functionalities in the watchFor variable, line 4 of init.lua

EDIT: If you feel a little lag with the caps_lock, you can do the following:
in karabiner.json map caps_lock to fn and fn to caps_lock, then delete the "standalone_keys" mappings and set the "standalone_keys_delay_miliseconds" to 0

"simple_modifications": {
"caps_lock": "fn",
"fn": "caps_lock"
}

Hi,

Thank you so much for your work! I have a question regarding the quick press of the CapsLock to activate it. The code you provided didn't work for me.

The following is my JSON file:

{
    "profiles": [
        {
            "devices": [],
            "fn_function_keys": {
                "f1": "display_brightness_decrement",
                "f10": "mute",
                "f11": "volume_decrement",
                "f12": "volume_increment",
                "f2": "display_brightness_increment",
                "f3": "mission_control",
                "f4": "launchpad",
                "f5": "illumination_decrement",
                "f6": "illumination_increment",
                "f7": "rewind",
                "f8": "play_or_pause",
                "f9": "fastforward"
            },
            "name": "Default profile",
            "one_to_many_mappings": {},
            "selected": true,
            "simple_modifications": {
                "caps_lock": "fn"
            },
            "standalone_keys": {
                "caps_lock": "caps_lock"
            },
            "virtual_hid_keyboard": {
                "caps_lock_delay_milliseconds": 0,
                "keyboard_type": "ansi",
                "standalone_keys_delay_milliseconds": 100
            }
        }
    ]
}

Please let me know what I did wrong. Thank you in advance!

You have to use the version of Karabiner-Elements by @wwwjfy for this to work. See https://github.com/wwwjfy/Karabiner-Elements/releases for releases and pqrs-org/Karabiner-Elements#247 for the pull request.

More accurately, it's the standalone_keys bit that requires the alternative version.

Not work for me. I use Karabiner-Elements v0.90.77 and Hammerspoon v0.9.52.

I change module.debugging = false to module.debugging = true, but no message in the Hammerspoon console.

This is just plain awesome. Thanks a lot!

very helpful~ Thanks a lot~

something related Hammerspoon/hammerspoon#1252 (comment)

It works. Thanks a lot!

Love it! Can't wait until vi mode comes back into karabiner-elements, but until then, thank you 👌

Thanks!

@sengngykouch hey i'm sorry i didn't answer on time, I never saw the notification. I think the solution is what alf says.

You have to use the version of Karabiner-Elements by @wwwjfy for this to work. See https://github.com/wwwjfy/Karabiner-Elements/releases for releases and pqrs-org/Karabiner-Elements#247 for the pull request.