Metakey setup macOS / use CAPS LOCK to open or switch to apps with Hammerspoon and Karabiner

init.lua

-- A global variable for the Hyper Mode
hyper = hs.hotkey.modal.new({}, 'F17')


-- Enter Hyper Mode when F18 (Hyper/Capslock) is pressed
function enterHyperMode()
  hyper.triggered = false
  hyper:enter()
end

-- Leave Hyper Mode when F18 (Hyper/Capslock) is pressed,
-- send ESCAPE if no other keys are pressed.
function exitHyperMode()
  hyper:exit()
  if not hyper.triggered then
    hs.eventtap.keyStroke({}, 'ESCAPE')
  end
end

-- Bind the Hyper key
f18 = hs.hotkey.bind({}, 'F18', enterHyperMode, exitHyperMode)


-- Setup shortcuts, press "CAPS LOCK + X" to activate one
--
hyper:bind({}, "R", function()
  hs.reload()
end)
hs.alert.show("Config Re-loaded")

-- Lock the Screen
hyper:bind({}, "L", function()
  hs.caffeinate.lockScreen()
end)


function forceLaunchOrFocus(appName)
  -- first focus with hammerspoon
  hs.application.launchOrFocus(appName)

  -- clear timer if exists
  if ext.cache.launchTimer then ext.cache.launchTimer:stop() end

  -- wait 500ms for window to appear and try hard to show the window
  ext.cache.launchTimer = hs.timer.doAfter(0.5, function()
    local frontmostApp     = hs.application.frontmostApplication()
    local frontmostWindows = hs.fnutils.filter(frontmostApp:allWindows(), function(win) return win:isStandard() end)

    -- break if this app is not frontmost (when/why?)
    if frontmostApp:title() ~= appName then
      print('Expected app in front: ' .. appName .. ' got: ' .. frontmostApp:title())
      return
    end

    if #frontmostWindows == 0 then
      -- check if there's app name in window menu (Calendar, Messages, etc...)
      if frontmostApp:findMenuItem({ 'Window', appName }) then
        -- select it, usually moves to space with this window
        frontmostApp:selectMenuItem({ 'Window', appName })
      else
        -- otherwise send cmd-n to create new window
        hs.eventtap.keyStroke({ 'cmd' }, 'n')
      end
    end
  end)
end

-- smart app launch or focus or cycle windows
function smartLaunchOrFocus(launchApps)
  local frontmostWindow = hs.window.frontmostWindow()
  local runningApps     = hs.application.runningApplications()
  local runningWindows  = {}

  -- filter running applications by apps array
  local runningApps = hs.fnutils.map(launchApps, function(launchApp)
    return hs.application.get(launchApp)
  end)

  -- create table of sorted windows per application
  hs.fnutils.each(runningApps, function(runningApp)
    local standardWindows = hs.fnutils.filter(runningApp:allWindows(), function(win)
      return win:isStandard()
    end)

    table.sort(standardWindows, function(a, b) return a:id() < b:id() end)

    runningWindows = standardWindows
  end)

  if #runningApps == 0 then
    -- if no apps are running then launch first one in list
    forceLaunchOrFocus(launchApps[1])
  elseif #runningWindows == 0 then
    -- if some apps are running, but no windows - force create one
    forceLaunchOrFocus(runningApps[1]:title())
  else
    -- check if one of windows is already focused
    local currentIndex = hs.fnutils.indexOf(runningWindows, frontmostWindow)

    if not currentIndex then
      -- if none of them is selected focus the first one
      runningWindows[1]:focus()
    else
      -- otherwise cycle through all the windows
      local newIndex = currentIndex + 1
      if newIndex > #runningWindows then newIndex = 1 end

      runningWindows[newIndex]:focus()
    end
  end
end


hyper:bind({}, "A", function()
  smartLaunchOrFocus({"Atom"})
end)

hyper:bind({}, "C", function()
  smartLaunchOrFocus({"Google Chrome"})
end)

hyper:bind({}, "E", function()
  hs.application.launchOrFocus("ExpressVPN")
end)

hyper:bind({}, "F", function()
hs.application.launchOrFocus("Firefox")
end)

hyper:bind({}, "G", function()
  smartLaunchOrFocus({"GitX"})
end)

hyper:bind({}, "H", function()
hs.application.launchOrFocus("HTTP Toolkit")
end)

hyper:bind({}, "T", function()
  smartLaunchOrFocus({"iTerm"})
end)

hyper:bind({}, "P", function()
  hs.application.launchOrFocus("Postman")
end)

hyper:bind({}, "Q", function()
  hs.application.launchOrFocus("Qbserve")
end)

hyper:bind({}, "S", function()
  hs.application.launchOrFocus("Slack")
end)

hyper:bind({}, "Z", function()
  hs.application.launchOrFocus("zoom.us")
end)

For this hammerspoon config to work, you have to map CAPS LOCK to F18 with Karabiner-Elements.

http://www.hammerspoon.org/

https://github.com/pqrs-org/Karabiner-Elements