Remapping keys with Karabiner Elements and Hammerspoon

[jannis-baum]

The DistributedNotification API introduced in kV 33 allows us to remap keys by modes with the help of Karabiner Elements and Hammerspoon.

I will use this thread to illustrate this at the example of remapping q in Normal mode in Safari to open a new tab.

Setting up a Karabiner variable to reflect kV's mode

The first step is getting Karabiner to know whether kV is in Normal mode. This is done by listening to the kindaVimDidEnterNormalMode and kindaVimDidExitNormalMode notifications with Hammerspoon and using Karabiner's CLI to set a Karabiner variable accordingly. Karabiner's CLI can be found in /Library/Application\\ Support/org.pqrs/Karabiner-Elements/bin/karabiner_cli but may be at a different location depending on your installation. Add the following to your Hammerspoon config, e.g. in ~/.hammerspoon/init.lua:

kVNormalEnterWatcher = hs.distributednotifications.new(function(name, object, userInfo)
    hs.execute('/Library/Application\\ Support/org.pqrs/Karabiner-Elements/bin/karabiner_cli --set-variables "{\\"kVNormal\\":1}"')
end, 'kindaVimDidEnterNormalMode')
kVNormalEnterWatcher:start()

kVNormalExitWatcher = hs.distributednotifications.new(function(name, object, userInfo)
    hs.execute('/Library/Application\\ Support/org.pqrs/Karabiner-Elements/bin/karabiner_cli --set-variables "{\\"kVNormal\\":0}"')
end, 'kindaVimDidExitNormalMode')
kVNormalExitWatcher:start()

With this config loaded, Karabiner will have the variable kVNormal set to 1 or 0 depending on whether kV is in normal mode. You can observe the variable with Karabiner's EventViewer App to verify everything is working correctly.

Remapping the key

With this variable working, you can use it as a condition in a complex modification in Karabiner. The easiest way to configure Karabiner is using goku, which provides more concise .edn syntax over Karabiner's .json. The following snippet in your ~/.config/karabiner.edn is enough to achieve our goal of remapping q in Normal mode in Safari to open a new tab, i.e. to cmd+t.

{
  :applications {
    :safari ["^com\\.apple\\.Safari$"]}

  :main [
    {:des "safari normal mode" :rules [
      [:condis :safari ["kVNormal" 1]]
        [:q :!Ct]]}
  ]
}

With this in your karabiner.edn, run goku and your remapping will be live!

Note: Make sure you have a Karabiner profile named Default or set up a different profile name with goku.

Note 2: For command+t to actually arrive at Safari, you need to enable Passthrough for command in kV's General preferences.

[haveanicedavid]

whoa - this is awesome! You could make entire app-specific utilities - i’ll definitely be looking into this more later

[jannis-baum]

i’ll definitely be looking into this more later

Share if you come up with something cool!