A Hammerspoon script that allows actions to be bound to quadrants on the trackpad

Touchpad.lua

--[[
Name:          Touchpad Control
Author:        James Doyle <james2doyle@gmail.com>
Description:   Hook into events/gestures that are triggered on the trackpad
Installation:  Just require this file in your Hammerspoon init.lua file
Usage:
    Bind the click actions or swipe actions to events
]]--

local trackpad_actions = {}
trackpad_actions["double_click"] = {}
trackpad_actions["triple_click"] = {
  top_left = { mod = { "cmd" }, press = "w", name = "close window" },
  bottom_left = { mod = { "cmd" }, press = "m", name = "minimize window" }
}
trackpad_actions["swipe"] = {
  {
    start = "top_left",
    stop = "bottom_left",
    name = "decrease volume",
    action = function()
      local audio_output = hs.audiodevice.defaultOutputDevice()
      local volume = audio_output:outputVolume()
      audio_output:setOutputVolume(volume - 5.0)
    end
  },
  {
    start = "bottom_left",
    stop = "top_left",
    name = "increase volume",
    action = function()
      local audio_output = hs.audiodevice.defaultOutputDevice()
      local volume = audio_output:outputVolume()
      audio_output:setOutputVolume(volume + 5.0)
    end
  }
}

-- trackpad layout
-- |0,1           1,1|
-- |                 |
-- |                 |
-- |     0.5,0.5     |
-- |                 |
-- |                 |
-- |0,0           1,0|


local log = hs.logger.new('trackpad-module', 'debug')
log:d("i am debugging trackpad-module")

local top_left = { start = { x = 0, y = 0.75 }, stop = { x = 0.25, y = 1 } }
local top_right = { start = { x = 0.75, y = 0.75 }, stop = { x = 1, y = 1 } }
local bottom_left = { start = { x = 0, y = 0 }, stop = { x = 0.25, y = 0.25 } }
local bottom_right = { start = { x = 0.75, y = 0 }, stop = { x = 1, y = 0.75 } }

-- causes eventtap to respond to *all* events that it can, except keyboard stuff
local eventList = {
  "all",
  hs.eventtap.event.types.flagsChanged,
  hs.eventtap.event.types.keyDown,
  hs.eventtap.event.types.keyUp,
  hs.eventtap.event.types.mouseMoved
}

local lastEvent = nil

local click_counter = 0

local start_quadrant = nil
local end_quadrant = nil

-- debounce the callback that is run after touching is complete
local timer = hs.timer.doAfter(0.2, function()
  if start_quadrant ~= nil and end_quadrant ~= nil then
    hs.fnutils.each(trackpad_actions.swipe, function (action)
      if start_quadrant == action.start and end_quadrant == action.stop then
        log:d("swipe, " .. action.name)
        action.action()
      end
    end)

    if click_counter == 2 then
      for quadrant,action in hs.fnutils.sortByKeys(trackpad_actions.double_click) do
        if start_quadrant == quadrant and end_quadrant == quadrant then
          log:d("double_click, " .. action.name)
          hs.eventtap.keyStroke(action.mod, action.press)
        end
      end
    end

    if click_counter == 3 then
      for quadrant,action in hs.fnutils.sortByKeys(trackpad_actions.triple_click) do
        if start_quadrant == quadrant and end_quadrant == quadrant then
          log:d("triple_click, " .. action.name)
          hs.eventtap.keyStroke(action.mod, action.press)
        end
      end
    end

    click_counter = 0
    start_quadrant = nil
    end_quadrant = nil
  end
end):stop()

function get_position(x, y)
  if x > top_left.start.x and y > top_left.start.y and x < top_left.stop.x and y < top_left.stop.y then
    return "top_left"
  end

  if x > top_right.start.x and y > top_right.start.y and x < top_right.stop.x and y < top_right.stop.y then
    return "top_right"
  end

  if x > bottom_left.start.x and y > bottom_left.start.y and x < bottom_left.stop.x and y < bottom_left.stop.y then
    return "bottom_left"
  end

  if x > bottom_right.start.x and y > bottom_right.start.y and x < bottom_right.stop.x and y < bottom_right.stop.y then
    return "bottom_right"
  end

  return "center"
end

hs.eventtap.new({hs.eventtap.event.types.gesture, hs.eventtap.event.types.tabletPointer}, function (e)
  local details = e:getTouches()

  if details[1] and details[1]["phase"] == "began" then
    click_counter = click_counter + 1
  end

  if start_quadrant == nil and details[1] and details[1]["phase"] == "began" then
    local x = details[1]["normalizedPosition"]["x"]
    local y = details[1]["normalizedPosition"]["y"]

    start_quadrant = get_position(x, y)
  end

  if end_quadrant == nil and details[1] and details[1]["phase"] == "ended" then
    local x = details[1]["normalizedPosition"]["x"]
    local y = details[1]["normalizedPosition"]["y"]

    end_quadrant = get_position(x, y)
  end

  timer:stop()
  timer:start()
end):start()