Fix layer switching from tap dances by redoing the keymap lookup (#17935)

tests/tap_dance/tap_dance_layers/tap_dance_defs.c

@@ -0,0 +1,97 @@
+// Copyright 2022 Sergey Vlasov (@sigprof)
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include "quantum.h"
+#include "tap_dance_defs.h"
+
+// Implement custom keycodes which are used to check that the layer switching
+// behaves properly.
+bool process_record_user(uint16_t keycode, keyrecord_t *record) {
+    switch (keycode) {
+        case FAST_AB:
+        case SLOW_AB:
+            if (record->event.pressed) {
+                tap_code(KC_A);
+            } else {
+                tap_code(KC_B);
+            }
+            return keycode == SLOW_AB;
+        case FAST_CD:
+        case SLOW_CD:
+            if (record->event.pressed) {
+                tap_code(KC_C);
+            } else {
+                tap_code(KC_D);
+            }
+            return keycode == SLOW_CD;
+    }
+    return true;
+}
+
+// Implement a custom tap dance with the following behavior:
+// - single tap: KC_APP
+// - single hold: MO(1)
+// - double tap/hold: KC_RCTL
+// (The single tap and hold actions are mostly equivalent to LT(1, KC_APP).)
+
+enum lt_app_state {
+    LTA_NONE,
+    LTA_SINGLE_TAP,
+    LTA_SINGLE_HOLD,
+    LTA_DOUBLE_HOLD,
+};
+
+static enum lt_app_state saved_lt_app_state;
+
+static enum lt_app_state get_lt_app_state(qk_tap_dance_state_t *state) {
+    if (state->count == 1) {
+        if (!state->pressed) {
+            return LTA_SINGLE_TAP;
+        } else {
+            return LTA_SINGLE_HOLD;
+        }
+    } else if (state->count == 2) {
+        return LTA_DOUBLE_HOLD;
+    } else {
+        return LTA_NONE;
+    }
+}
+
+static void lt_app_finished(qk_tap_dance_state_t *state, void *user_data) {
+    saved_lt_app_state = get_lt_app_state(state);
+    switch (saved_lt_app_state) {
+        case LTA_NONE:
+            break;
+        case LTA_SINGLE_TAP:
+            register_code(KC_APP);
+            break;
+        case LTA_SINGLE_HOLD:
+            layer_on(1);
+            break;
+        case LTA_DOUBLE_HOLD:
+            register_code(KC_RCTL);
+            break;
+    }
+}
+
+static void lt_app_reset(qk_tap_dance_state_t *state, void *user_data) {
+    switch (saved_lt_app_state) {
+        case LTA_NONE:
+            break;
+        case LTA_SINGLE_TAP:
+            unregister_code(KC_APP);
+            break;
+        case LTA_SINGLE_HOLD:
+            layer_off(1);
+            break;
+        case LTA_DOUBLE_HOLD:
+            unregister_code(KC_RCTL);
+            break;
+    }
+}
+
+qk_tap_dance_action_t tap_dance_actions[] = {
+    [TD_L_MOVE] = ACTION_TAP_DANCE_LAYER_MOVE(KC_APP, 1),
+    [TD_L_TOGG] = ACTION_TAP_DANCE_LAYER_TOGGLE(KC_APP, 1),
+    [TD_LT_APP] = ACTION_TAP_DANCE_FN_ADVANCED(NULL, lt_app_finished, lt_app_reset),
+};