Hammerspoon rules for binding pedals

init.lua

require('util')

pedal_rules = {
   l = {
      {
         name = "Google Meet (show chat)",
         predicate = isAppRunning("Google Chrome"),
         action = hs.fnutils.partial(dispatchCommandToChrome, {'ctrl', 'cmd'}, 'c'),
      },
      {
         name = "Firefox (prev tab)",
         predicate = isAppFront("Firefox"),
         action = hs.fnutils.partial(hs.eventtap.keyStroke, {'shift', 'cmd'}, '['),
      },
      {
         name = "Fallback",
         predicate = true,
         action = hs.fnutils.partial(hs.eventtap.keyStroke, {}, 'a'),
      },
   },
   m = {
      {
         name = "Google Meet (mute/unmute)",
         predicate = isAppRunning("Google Chrome"),
         action = hs.fnutils.partial(dispatchCommandToChrome, {'cmd'}, 'd'),
      },
      {
         name = "Firefox (next tab)",
         predicate = isAppFront("Firefox"),
         action = hs.fnutils.partial(hs.eventtap.keyStroke, {'cmd', 'shift'}, ']'),
      },
      {
         name = "Fallback",
         predicate = true,
         action = hs.fnutils.partial(hs.eventtap.keyStroke, {}, 'b'),
      },
   },
   r = {
      {
         name = "Google Meet (camera on/off)",
         predicate = isAppRunning("Google Chrome"),
         action = hs.fnutils.partial(dispatchCommandToChrome, {'ctrl', 'cmd'}, 'e'),
      },
      {
         name = "Firefox (close tab)",
         predicate = isAppFront("Firefox"),
         action = hs.fnutils.partial(hs.eventtap.keyStroke, {'cmd'}, 'w'),
      },
      {
         name = "Fallback",
         predicate = true,
         action = hs.fnutils.partial(hs.eventtap.keyStroke, {}, 'c'),
      },
   },
}

pedal_config = {
   l = 'F16',
   m = 'F17',
   r = 'F18',
}

bindPedals(pedal_config, pedal_rules)

util.lua

function isAppRunning(appName)
   return (function() return hs.application.find(appName) ~= nil end)
end

function isAppFront(appName)
   return (function() return hs.application.frontmostApplication():name() == appName end)
end

function dispatchCommandToChrome(modifier, key)
   -- return false if one can't, otherwise true
   if (isAppRunning("Google Chrome")()) then
      if (hs.window.focusedWindow():application():name() ~= "Google Chrome") then
         hs.application.launchOrFocus("Google Chrome")
      end
      hs.eventtap.keyStroke(modifier, key)
   else
      return false
   end
end

function bindPedals(config, rules)
   -- config takes table that maps l, m and r to keystrokes
   -- rules takes a table containing l, m, r and then a list-like
   -- table of rules to be executed sequentially
   --
   -- each rule is a table containing:
   -- name - just for personal reference
   -- predicate - function or value to decide if rule should run
   -- action - what the rule should do
   for pedal, mapping in pairs(config) do
      hs.hotkey.bind({}, mapping, function()
         for _, rule in pairs(rules[pedal]) do
            if type(rule.predicate) == "function" then
               if rule.predicate() then
                  rule.action()
                  break
               end
            else
               if rule.predicate ~= false then
                  rule.action()
                  break
               end
            end
         end
      end)
   end
end