Mapping keys to set different input languages on macOS

2021-08-15

Prerequisite

• You need Karabiner installed.

Final Goal

• Press Left Command to set Mac's input method to English.
• Press Right Command to set Mac's input method to Korean.
• Any other shortcut combinations would perform as usual.

Instructions

• Go to ~/.config/karabiner/assets/complex_modifications. You can click Command+Shift+G within Finder to open a goto window.
• Create a JSON file like the following here (open any text editor and save it as filename.json).
• Go to Karabiner-Elements.app → Complex Modifications and press add rules.
• Click the rules that you want to enable. The above text file will show under Multilingual Input Methods.

{
  "title": "Multilingual Input Methods",
  "rules": [
    {
      "description": "R Command to 한글",
      "manipulators": [
        {
          "type": "basic",
          "from": {
            "key_code": "right_command",
            "modifiers": { "optional": ["any"] }
          },
          "to": [{ "key_code": "right_command", "lazy": true }],
          "to_if_alone": [
            {
              "select_input_source": { "language": "^ko$" }
            }
          ]
        }
      ]
    },
    {
      "description": "L Command to English",
      "manipulators": [
        {
          "type": "basic",
          "from": {
            "key_code": "left_command",
            "modifiers": { "optional": ["any"] }
          },
          "to": [{ "key_code": "left_command", "lazy": true }],
          "to_if_alone": [
            {
              "select_input_source": { "language": "^en$" }
            }
          ]
        }
      ]
    }
  ]
}

Configuring more languages

• Add a JSON Property with your language of choice. The language identifier is likely some combination of ISO 639 and ISO 3166 (i.e., BCP 47).
• https://karabiner-elements.pqrs.org/docs/json/complex-modifications-manipulator-definition/to/select-input-source/

Update Mar 7th, 2022

• If you're bilingual, try looking into Eikana.
• I switched to Eikana + Gureum configuration; there's a notorious 자소 분리 bug in macOS Korean Keyboard.