Karabiner Elements and Hammerspoon on MacOS Sierra

init.lua

-- ln -s ~/repos/config/init.lua ~/.hammerspoon/init.lua

-- Global variable for the Command Mode
cMode = hs.hotkey.modal.new({}, "F17")

-- Global variable for Delete Mode
dMode = hs.hotkey.modal.new({}, 'F20')

-- Global variable for Select Mode
sMode = hs.hotkey.modal.new({}, 'F19')

-- Global variable to store last Command
lastCommand = nil

function callLast()
  return lastCommand()
end

-- Command Mode bindings
cModeBindings = {
  -- up
  { {}, 'i', {}, 'up' },
  { {'shift'}, 'i', {'shift'}, 'up' },
  { {'cmd'}, 'i', {'cmd'}, 'up' },
  { {'alt'}, 'i', {}, 'pageup' },
  -- down
  { {}, 'k', {}, 'down' },
  { {'shift'}, 'k', {'shift'}, 'down' },
  { {'cmd'}, 'k', {'cmd'}, 'down' },
  { {'alt'}, 'k', {}, 'pagedown' },
  -- left
  { {}, 'j', {}, 'left' },
  { {'shift'}, 'j', {'shift'}, 'left' },
  { {'cmd'}, 'j', {'cmd'}, 'left' },
  { {'alt'}, 'j', {'alt'}, 'left' },
  -- right
  { {}, 'l', {}, 'right' },
  { {'shift'}, 'l', {'shift'}, 'right' },
  { {'cmd'}, 'l', {'cmd'}, 'right' },
  { {'alt'}, 'l', {'alt'}, 'right' },
  -- delete left
  { {}, 'n', {}, 'delete' },
  { {'alt'}, 'n', {'alt'}, 'delete' },
  { {'cmd'}, 'n', {'cmd'}, 'delete' },
  -- delete right
  { {}, 'm', {}, 'forwarddelete' },
  { {'alt'}, 'm', {'alt'}, 'forwarddelete' },
  { {'cmd'}, 'm', {'cmd'}, 'forwarddelete' },
}

-- Select Mode bindings
sModeBindings = {
  -- up
  { {}, 'i', {'shift'}, 'up' },
  { {'cmd'}, 'i', {'cmd', 'shift'}, 'up' },
  { {'alt'}, 'i', {'shift'}, 'pageup' },
  -- down
  { {}, 'k', {'shift'}, 'down' },
  { {'cmd'}, 'k', {'cmd', 'shift'}, 'down' },
  { {'alt'}, 'k', {'shift'}, 'pagedown' },
  -- left
  { {}, 'j', {'shift'}, 'left' },
  { {'cmd'}, 'j', {'cmd', 'shift'}, 'left' },
  { {'alt'}, 'j', {'alt', 'shift'}, 'left' },
  -- right
  { {}, 'l', {'shift'}, 'right' },
  { {'cmd'}, 'l', {'cmd', 'shift'}, 'right' },
  { {'alt'}, 'l', {'alt', 'shift'}, 'right' },
  -- delete left
  { {}, 'n', {}, 'delete' },
  { {'alt'}, 'n', {'alt'}, 'delete' },
  { {'cmd'}, 'n', {'cmd'}, 'delete' },
  -- delete right
  { {}, 'm', {}, 'forwarddelete' },
  { {'alt'}, 'm', {'alt'}, 'forwarddelete' },
  { {'cmd'}, 'm', {'cmd'}, 'forwarddelete' },
}

-- Bind command mode keys
for i, bnd in ipairs(cModeBindings) do
  local function eb()
    hs.eventtap.keyStroke(bnd[3], bnd[4])
    cMode.triggered = true
  end

  cMode:bind(bnd[1], bnd[2], eb, nil, eb)
end

-- Command Mode: bind Delete Mode
cMode:bind({}, 'd', nil, function()
  hs.eventtap.keyStroke({}, 'F20')
  cMode.triggered = true
end)

-- Delete Mode: delete line
function dLine()
  hs.eventtap.keyStroke({}, 'space')
  hs.eventtap.keyStroke({'cmd'}, 'right')
  hs.eventtap.keyStroke({'cmd'}, 'delete')
  hs.eventtap.keyStroke({'cmd'}, 'forwarddelete')
  lastCommand = dLine
  dMode.exit()
end

-- Delete Mode: delete word
function dWordBack()
  hs.eventtap.keyStroke({'alt'}, 'left')
  hs.eventtap.keyStroke({'alt'}, 'forwarddelete')
  hs.eventtap.keyStroke({}, 'delete')
  lastCommand = dWordBack
  dMode.exit()
end

-- Delete Mode: delete word forwards
function dWordForward()
  hs.eventtap.keyStroke({'alt'}, 'right')
  hs.eventtap.keyStroke({'alt'}, 'delete')
  hs.eventtap.keyStroke({}, 'forwarddelete')
  lastCommand = dWordForward
  dMode.exit()
end

-- Delete Mode bindings
dModeBindings = {
  { {}, 'l', nil, dLine },
  { {}, 'b', nil, dWordBack },
  { {}, 'w', nil, dWordForward }
}

-- Bind Delete Mode bindings
for i, bnd in ipairs(dModeBindings) do
  dMode:bind(bnd[1], bnd[2], nil, bnd[4])
end

-- Command Mode: bind Select Mode
cMode:bind({}, 'v', nil, function()
  hs.eventtap.keyStroke({}, 'F19')
  cMode.triggered = true
end)

-- Bind Select Mode bindings
for i, bnd in ipairs(sModeBindings) do
  local function eb()
    hs.eventtap.keyStroke(bnd[3], bnd[4])
  end

  sMode:bind(bnd[1], bnd[2], eb, nil, eb)
end

-- Enter Command Mode
cModePressed = function()
  cMode.triggered = false
  cMode:enter()
end

-- Leave Command Mode
-- Escape if no other keys are pressed
cModeReleased = function()
  dMode:exit()
  sMode:exit()
  cMode:exit()
  if not cMode.triggered then
    hs.eventtap.keyStroke({}, 'ESCAPE')
  end
end

-- Bind Command Mode
f18 = hs.hotkey.bind({}, 'F18', cModePressed, cModeReleased)

-- Command Mode: repeat last Command
cMode:bind({}, '.', callLast)

karabiner.json

{
    "_comment": "ln -s ~/repos/config/karabiner.json ~/.karabiner.d/configuration/karabiner.json",
    "profiles": [
        {
            "name": "Default profile",
            "selected": true,
            "simple_modifications": {
                "caps_lock": "f18",
                "escape": "caps_lock",
                "right_option": "f17"
            }
        }
    ]
}

If anyone is checking this out, make sure to use Hammerspoon v.0.9.48. There is an issue effecting timing of the repeanfn in v.0.9.49 and greater.

Hammerspoon/hammerspoon#1087