Fix Tapping: release key immediately but modifier #65

- See https://github.com/tmk/tmk_keyboard/issues/60
- **Except for modifiers** a key pressed before the tapping starts should be released immediately
- 'Mod-Tap key'(like shift-;) didn't work from this fix: 4d0b3aa Fix Tapping: release of a key pressed before tap
This key sequence should register ':', not ';'. With the fix Shift is
released before settlement of tapping, this registers ';'.
    Shift   ~~___~~~~~~~
    ;(Tap)  ~~~____~~~~

common/action_tapping.c

@@ -1,7 +1,9 @@
 #include <stdint.h>
 #include <stdbool.h>
 #include "action.h"
+#include "action_layer.h"
 #include "action_tapping.h"
+#include "keycode.h"
 #include "timer.h"
 
 #ifdef DEBUG_ACTION
@@ -95,22 +97,40 @@ bool process_tapping(keyrecord_t *keyp)
                     return false;
                 }
 #if TAPPING_TERM >= 500
-                /* This can settle mod/fn state fast but may prevent from typing fast. */
+                /* Process a key typed within TAPPING_TERM
-                else if (!event.pressed && waiting_buffer_typed(event)) {
+                 * This can register the key before settlement of tapping,
-                    // other key typed. not tap.
+                 * useful for long TAPPING_TERM but may prevent fast typing.
+                 */
+                else if (IS_RELEASED(event) && waiting_buffer_typed(event)) {
                     debug("Tapping: End. No tap. Interfered by typing key\n");
                     process_action(&tapping_key);
                     tapping_key = (keyrecord_t){};
                     debug_tapping_key();
-
                     // enqueue
                     return false;
                 }
 #endif
-                /* release a key pressed before tapping */
+                /* Process release event of a key pressed before tapping starts
-                else if (!event.pressed && !waiting_buffer_typed(event)) {
+                 * Without this unexpected repeating will occur with having fast repeating setting
-                    /* Unexpected repeating occurs unless this event is processed immedately. */
+                 * https://github.com/tmk/tmk_keyboard/issues/60
-                    debug("Tapping: release a key pressed before tapping\n");
+                 */
+                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);
+                    switch (action.kind.id) {
+                        case ACT_LMODS:
+                        case ACT_RMODS:
+                            if (action.key.mods && !action.key.code) return false;
+                            if (IS_MOD(action.key.code)) return false;
+                            break;
+                        case ACT_LMODS_TAP:
+                        case ACT_RMODS_TAP:
+                            if (action.key.mods && keyp->tap.count == 0) return false;
+                            if (IS_MOD(action.key.code)) return false;
+                            break;
+                    }
+                    // Release of key should be process immediately.
+                    debug("Tapping: release event of a key pressed before tapping\n");
                     process_action(keyp);
                     return true;
                 }

common/keyboard.h

@@ -42,16 +42,15 @@ typedef struct {
 /* equivalent test of key_t */
 #define KEYEQ(keya, keyb)       ((keya).row == (keyb).row && (keya).col == (keyb).col)
 
-/* (time == 0) means no event and assumes matrix has no 255 line. */
+/* Rules for No Event:
-#define IS_NOEVENT(event)       ((event).time == 0 || ((event).key.row == 255 && (event).key.col == 255))
+ * 1) (time == 0) to handle (keyevent_t){} as empty event
+ * 2) Matrix(255, 255) to make TICK event available
+ */
+static inline bool IS_NOEVENT(keyevent_t event) { return event.time == 0 || (event.key.row == 255 && event.key.col == 255); }
+static inline bool IS_PRESSED(keyevent_t event) { return (!IS_NOEVENT(event) && event.pressed); }
+static inline bool IS_RELEASED(keyevent_t event) { return (!IS_NOEVENT(event) && !event.pressed); }
 
-#define NOEVENT                 (keyevent_t){           \
+/* Tick event */
-    .key = (key_t){ .row = 255, .col = 255 },           \
-    .pressed = false,                                   \
-    .time = 0                                           \
-}
-
-/* tick event */
 #define TICK                    (keyevent_t){           \
     .key = (key_t){ .row = 255, .col = 255 },           \
     .pressed = false,                                   \