ergodox-key-combination-sample.c

#define MOD_LCTL 0x1
#define MOD_LGUI 0x2
#define MOD_LSFT 0x4
#define MOD_LALT 0x8

static uint16_t mod_state = 0;

// {mod_state, remap_src, remap_dest}
const uint16_t key_combo[][3] = {
  {(MOD_LCTL|MOD_LGUI), KC_H, KC_LEFT},
  {(MOD_LCTL|MOD_LGUI), KC_J, KC_DOWN},
  {(MOD_LCTL|MOD_LGUI), KC_K, KC_UP},
  {(MOD_LCTL|MOD_LGUI), KC_L, KC_RGHT}
};

bool process_record_user(uint16_t keycode, keyrecord_t *record) {
  
  /* amazing your code */
  
  if (keycode == KC_LCTL) {
    if (record->event.pressed) {
      mod_state |= MOD_LCTL;
    } else {
      mod_state &= ~(MOD_LCTL);
    }
  }

  if (keycode == KC_LGUI) {
    if (record->event.pressed) {
      mod_state |= MOD_LGUI;
    } else {
      mod_state &= ~(MOD_LGUI);
    }
  }

  if (keycode == KC_LSFT) {
    if (record->event.pressed) {
      mod_state |= MOD_LSFT;
    } else {
      mod_state &= ~(MOD_LSFT);
    }
  }

  if (keycode == KC_LALT) {
    if (record->event.pressed) {
      mod_state |= MOD_LALT;
    } else {
      mod_state &= ~(MOD_LALT);
    }
  }

  for(int i = 0; i < sizeof(key_combo) / sizeof(key_combo[0]); i++) {
    if (mod_state == key_combo[i][0]) {
      if(keycode == key_combo[i][1]) {
        if (record->event.pressed) {
          clear_mods();
          register_code(key_combo[i][2]);
        } else {
          unregister_code(key_combo[i][2]);
        }
        return false;
      }
    }
  }
}