core: Fix for stuck key problem #441

- Idea form https://github.com/qmk/qmk_firmware/pull/182
- Define NO_TRACK_KEY_PRESS to get old behaviour
- This should resolve #105, #248, #397, #441 and FAQ entry: https://github.com/tmk/tmk_keyboard/wiki/FAQ-Keymap#modifierlayer-stuck

tmk_core/common/action.c

@@ -65,7 +65,7 @@ void process_action(keyrecord_t *record)
 
     if (IS_NOEVENT(event)) { return; }
 
-    action_t action = layer_switch_get_action(event.key);
+    action_t action = layer_switch_get_action(event);
     dprint("ACTION: "); debug_action(action);
 #ifndef NO_ACTION_LAYER
     dprint(" layer_state: "); layer_debug();
@@ -529,9 +529,9 @@ void clear_keyboard_but_mods(void)
 #endif
 }
 
-bool is_tap_key(keypos_t key)
+bool is_tap_key(keyevent_t event)
 {
-    action_t action = layer_switch_get_action(key);
+    action_t action = layer_switch_get_action(event);
 
     switch (action.kind.id) {
         case ACT_LMODS_TAP:

tmk_core/common/action.h

@@ -68,7 +68,7 @@ void unregister_mods(uint8_t mods);
 void clear_keyboard(void);
 void clear_keyboard_but_mods(void);
 void layer_switch(uint8_t new_layer);
-bool is_tap_key(keypos_t key);
+bool is_tap_key(keyevent_t event);
 
 /* debug */
 void debug_event(keyevent_t event);

tmk_core/common/action_layer.c

@@ -24,7 +24,9 @@ static void default_layer_state_set(uint32_t state)
     default_layer_state = state;
     hook_default_layer_change(default_layer_state);
     default_layer_debug(); debug("\n");
+#ifdef NO_TRACK_KEY_PRESS
     clear_keyboard_but_mods(); // To avoid stuck keys
+#endif
 }
 
 void default_layer_debug(void)
@@ -66,7 +68,9 @@ static void layer_state_set(uint32_t state)
     layer_state = state;
     hook_layer_change(layer_state);
     layer_debug(); dprintln();
+#ifdef NO_TRACK_KEY_PRESS
     clear_keyboard_but_mods(); // To avoid stuck keys
+#endif
 }
 
 void layer_clear(void)
@@ -115,7 +119,8 @@ void layer_debug(void)
 
 
 
-action_t layer_switch_get_action(keypos_t key)
+/* return layer effective for key at this time */
+static uint8_t current_layer_for_key(keypos_t key)
 {
     action_t action = ACTION_TRANSPARENT;
 
@@ -126,15 +131,34 @@ action_t layer_switch_get_action(keypos_t key)
         if (layers & (1UL<<i)) {
             action = action_for_key(i, key);
             if (action.code != (action_t)ACTION_TRANSPARENT.code) {
-                return action;
+                return i;
             }
         }
     }
     /* fall back to layer 0 */
-    action = action_for_key(0, key);
-    return action;
+    return 0;
 #else
-    action = action_for_key(biton32(default_layer_state), key);
-    return action;
+    return biton32(default_layer_state);
 #endif
 }
+
+
+#ifndef NO_TRACK_KEY_PRESS
+/* record layer on where key is pressed */
+static uint8_t layer_pressed[MATRIX_ROWS][MATRIX_COLS] = {};
+#endif
+action_t layer_switch_get_action(keyevent_t event)
+{
+    uint8_t layer = 0;
+#ifndef NO_TRACK_KEY_PRESS
+    if (event.pressed) {
+        layer = current_layer_for_key(event.key);
+        layer_pressed[event.key.row][event.key.col] = layer;
+    } else {
+        layer = layer_pressed[event.key.row][event.key.col];
+    }
+#else
+    layer = current_layer_for_key(event.key);
+#endif
+    return action_for_key(layer, event.key);
+}

tmk_core/common/action_layer.h

@@ -72,6 +72,6 @@ void layer_xor(uint32_t state);
 
 
 /* return action depending on current layer status */
-action_t layer_switch_get_action(keypos_t key);
+action_t layer_switch_get_action(keyevent_t key);
 
 #endif

tmk_core/common/action_tapping.c

@@ -115,7 +115,7 @@ bool process_tapping(keyrecord_t *keyp)
                  */
                 else if (IS_RELEASED(event) && !waiting_buffer_typed(event)) {
                     // Modifier should be retained till end of this tapping.
-                    action_t action = layer_switch_get_action(event.key);
+                    action_t action = layer_switch_get_action(event);
                     switch (action.kind.id) {
                         case ACT_LMODS:
                         case ACT_RMODS:
@@ -152,7 +152,7 @@ bool process_tapping(keyrecord_t *keyp)
                     debug_tapping_key();
                     return true;
                 }
-                else if (is_tap_key(event.key) && event.pressed) {
+                else if (is_tap_key(event) && event.pressed) {
                     if (tapping_key.tap.count > 1) {
                         debug("Tapping: Start new tap with releasing last tap(>1).\n");
                         // unregister key
@@ -196,7 +196,7 @@ bool process_tapping(keyrecord_t *keyp)
                     tapping_key = (keyrecord_t){};
                     return true;
                 }
-                else if (is_tap_key(event.key) && event.pressed) {
+                else if (is_tap_key(event) && event.pressed) {
                     if (tapping_key.tap.count > 1) {
                         debug("Tapping: Start new tap with releasing last timeout tap(>1).\n");
                         // unregister key
@@ -241,7 +241,7 @@ bool process_tapping(keyrecord_t *keyp)
                         tapping_key = *keyp;
                         return true;
                     }
-                } else if (is_tap_key(event.key)) {
+                } else if (is_tap_key(event)) {
                     // Sequential tap can be interfered with other tap key.
                     debug("Tapping: Start with interfering other tap.\n");
                     tapping_key = *keyp;
@@ -272,7 +272,7 @@ bool process_tapping(keyrecord_t *keyp)
     }
     // not tapping state
     else {
-        if (event.pressed && is_tap_key(event.key)) {
+        if (event.pressed && is_tap_key(event)) {
             debug("Tapping: Start(Press tap key).\n");
             tapping_key = *keyp;
             waiting_buffer_scan_tap();