keymap.c snippet: QMK LGUI hold as F(1).

keymap_snippet.c

const int GUILAY = 1;

typedef struct {
  bool layer_toggle;
  bool sticky;
} td_ta_state_t;

static void ang_tap_dance_ta_finished (qk_tap_dance_state_t *state, void *user_data) {
  td_ta_state_t *td_ta = (td_ta_state_t *) user_data;

  if (td_ta->sticky) {
    td_ta->sticky = false;
    td_ta->layer_toggle = false;
    layer_off (GUILAY);
    return;
  }

  if (state->count == 1 && !state->pressed) {
    register_code (KC_LGUI);
    td_ta->sticky = false;
    td_ta->layer_toggle = false;
  } else {
    td_ta->layer_toggle = true;
    layer_on (GUILAY);
    td_ta->sticky = 0; /*(state->count == 2);*/
  }
}

static void ang_tap_dance_ta_reset (qk_tap_dance_state_t *state, void *user_data) {
  td_ta_state_t *td_ta = (td_ta_state_t *) user_data;

  if (!td_ta->layer_toggle)
    unregister_code (KC_LGUI);
  if (!td_ta->sticky)
    layer_off (GUILAY);
}


qk_tap_dance_action_t tap_dance_actions[] = {
   [0]  = {
     .fn = { NULL, ang_tap_dance_ta_finished, ang_tap_dance_ta_reset },
     .user_data = (void *)&((td_ta_state_t) { false, false })
   }
};