★ Keychron K2 on macOS: fix Home and End keys

Issue: For whatever reason, the Home and End keys on my Keychron K2 do not work as intended on macOS.

Expectations vs Reality

For example, when using a text editor such as TextMate or a web browser like Chrome, I’d expect:

• Home to position the text cursor in the beginning of the line (à la C-a in emacs)
• End to position the text cursor in the end of the line (à la C-e in emacs)

The only way to provoke these effects out-of-the-box is by pressing, respectively, the Cmd + Left and Cmd + Right shortcuts, as you would normally do in a Macbook laptop native keyboard.

This is very annoying because it only happens in macOS¹: the Home and End keys work just fine in both Linux and Windows. A reddit user reported the same issue in /r/keychron, but the existing thread has no proposed solutions.

Enter Karabiner Elements

I’ve always heard good things about Karabiner Elements as a praised one-size-fits-all application for keyboards and macros in macOS, thus decided to give it a try. Bonus points: it is open source, released into the public domain.

Upon installing it with Homebrew Cask (brew install karabiner-elements), I executed it. Then I needed to give a bunch of permissions to the application via macOS Settings > Security & Privacy > Privacy > Input Monitoring. The following apps were whitelisted accordingly:

• karabiner_grabber
• karabiner_observer
• Karabiner-EventViewer.app: this one is optional, but useful for debugging

The app is straightforward to use. It allows you to do all sorts of reactions to key codes input events.

I had a simple idea: I wanted to map Home to Cmd + Left, and End to Cmd + Right.

Unfortunately these are considered “Complex modifications” because they map one origin key to two destination keys. “Simple modifications” are one-to-one key mappings. Why is it unfortunate? Because it doesn’t seem to be possible to do such mappings via the app UI. Apparently one needs to express those mappings in a .json file instead.

Ah, communities

Sure, no problem, I was about to do it but then I realized there’s an official website for community-maintained mappings. The website is well organized and curated. Why create something fully from scratch when I could just reuse an existing one?

I found a “Keychron K2” category which made me instantly happy but it turned out not to be useful, as there were only two defined mappings therein:

• Change Keychron K2 keyboard layout to more closely resemble an Apple keyboard
• Remap some Keychrom K2(US) keys to make it less painful to switch from Macbook(RU) keyboard

None of these mattered to me. Then I searched for home to cmd which led me to this entry, which had exactly the mappings I wanted:

Home and End

• Home to Command Left
• End to Command Right

Its resulting JSON looks roughly like this (irrelevant bits stripped for the sake of brevity):

{
  "title": "Home and End",
  "rules": [
    {
      "description": "Home to Command Left",
      "manipulators": [
        {
          "type": "basic",
          "from": {
              "key_code": "home"
            },
          "to": [
            {
            "key_code": "left_arrow",
            "modifiers": "command"
            }
          ]
        }
      ]
    },
    {
      "description": "End to Command Right",
      "manipulators": [
        {
          "type": "basic",
          "from": {
              "key_code": "end"
            },
          "to": [
            {
            "key_code": "right_arrow",
            "modifiers": "command"
            }
          ]
        }
      ]
    }
  ]
}

There’s conveniently an Import button in the website though, which automatically opens the mappings in Karabiner Elements, so I didn’t even need to copy and paste the JSON.

Verdict

End Result: It worked flawlessly! The only caveat is that from now on I need to keep the Karabiner Elements application running as a daemon, but it is well justified. Plus, if I ever need² to map additional keys in the future, now I already have a workflow in place to do so.

Karabiner is like having QMK purely at the software layer, which works for any keyboard whatsoever.