Reduce tap dance memory usage, move state out of data (#25415)

* Use less tap dance memory.

Use dynamically allocated sparse array for tap dance state, dynamically allocate tap dance state when needed and free it when the tap dance is done.

* new approach

* Use null, check for null

* Reformat with docker

* Use uint8 with idx rather than uint16 with keycode in state

* fix accidental change

* reformat

* Add null check

* add documentation tip suggested by tzarc

* Only allow tap dance state allocation on key down, not on key up

Co-authored-by: Sergey Vlasov <sigprof@gmail.com>

* Only allow tap dance allocation on key down, not on key up

Co-authored-by: Sergey Vlasov <sigprof@gmail.com>

* add user action required section

---------

Co-authored-by: Sergey Vlasov <sigprof@gmail.com>

1 files changed, 7 insertions, 4 deletions

diff --git a/quantum/process_keycode/process_tap_dance.h b/quantum/process_keycode/process_tap_dance.h
index 5cccbdf439..5a972cee5a 100644
--- a/quantum/process_keycode/process_tap_dance.h
+++ b/quantum/process_keycode/process_tap_dance.h
@@ -28,15 +28,16 @@ typedef struct {
 #ifndef NO_ACTION_ONESHOT
     uint8_t oneshot_mods;
 #endif
-    bool pressed : 1;
-    bool finished : 1;
-    bool interrupted : 1;
+    bool    pressed : 1;
+    bool    finished : 1;
+    bool    interrupted : 1;
+    bool    in_use : 1;
+    uint8_t index;
 } tap_dance_state_t;
 
 typedef void (*tap_dance_user_fn_t)(tap_dance_state_t *state, void *user_data);
 
 typedef struct tap_dance_action_t {
-    tap_dance_state_t state;
     struct {
         tap_dance_user_fn_t on_each_tap;
         tap_dance_user_fn_t on_dance_finished;
@@ -80,6 +81,8 @@ typedef struct {
 
 void reset_tap_dance(tap_dance_state_t *state);
 
+tap_dance_state_t *tap_dance_get_state(uint8_t tap_dance_idx);
+
 /* To be used internally */
 
 bool preprocess_tap_dance(uint16_t keycode, keyrecord_t *record);