zmk-lang-switch

This module:

• makes custom keyboard layouts possible in multi-language setups (e.g. colemak-dh for English, phonetic-colemak-dh for Russian while having only QWERTY and ЙЦУКЕН installed in OS)
• let's you have a language-independent symbolic layer (i.e. ? key is always ? be it on English or on Russian layout)

Usage

To load the module, add the following entries to remotes and projects in config/west.yml.

manifest:
  remotes:
    - name: zmkfirmware
      url-base: https://github.com/zmkfirmware
    - name: xopclabs
      url-base: https://github.com/xopclabs
  projects:
    - name: zmk
      remote: zmkfirmware
      revision: main
      import: app/west.yml
    - name: zmk-lang-switch
      remote: xopclabs
      revision: main
  self:
    path: config

Configuration

You'll need to define a keycode for language switching hotkey in your system (alt+shift for me on Linux and Windows). I also define layer id's with meaningful names. 3 behaviors (in .keymap file or in a separate .dtsi):

#define ENG 0
#define RU 1
#define LANGSW LA(LSHIFT)

Create a language switch behavior. You'll use it to switch to a target language layer like this &ls RU. When pressed, this behavior combines switching to language's layers with pressing LANGSW enough times to switch to target language.

Keep in mind that keyboard doesn't know anything about actual OS language! This means that "out of sync" situations might happen (keyboard thinks it's on ENG, but in reality OS is on Russian), which might be resolved by pressing LANGSW manually. This also means that you should define your keyboard layers in according to your OS' keyboard layout order.

ls: lang_switch {
    compatible = "zmk,behavior-lang-switch";
    #binding-cells = <1>;
    bindings = <&kp LANG_SW>;
    layers = <ENG RU>;
};

Create a language switch behavior that won't actually switch layer. You'll use it for the next behavior.

Create a language switch
ls_: lang_switch_no_layer {
    compatible = "zmk,behavior-lang-switch";
    #binding-cells = <1>;
    bindings = <&kp LANG_SW>;
    layers = <ENG RU>;
    no-layer-switch;
};

Create a press-on-lang behavior for each language. It assures that keycode will be pressed on a specified language. We could use this behavior as &kp_en QMARK, language will be switched to English briefly, only to press the question mark keycode (pressing &kp QMARK while having, for example, Russian layout turned on results in comma being typed instead)

kp_en: kp_on_eng {
    compatible = "zmk,behavior-kp-on-lang";
    #binding-cells = <1>;
    bindings = <&ls_ ENG>;
};

Finally, you can create a layer for each language (remeber the order!), assign a lang-switch keys (or a combo!) and create a separate language-independent symbolic layer (having them always pressed on English)

Links

• My personal zmk-config contains a more elaborate example