Fix Caps Word to treat mod-taps more consistently. (#17463)

* Fix Caps Word to treat mod-taps more consistently.

Previously, holding any mod-tap key while Caps Word is active stops Caps
Word, and this happens regardless of `caps_word_press_user()`. Yet for
regular mod keys, AltGr (KC_RALT) is ignored, Shift keys are passed to
`caps_word_press_user()` to determine whether to continue, and
similarly, a key `RSFT(KC_RALT)` representing Right Shift + Alt is
passed to `caps_word_press_user()` to determine whether to continue.

This commit makes held mod-tap keys consistent with regular mod keys:

* Holding a `RALT_T` mod-tap is ignored.
* When holding a shift mod-tap key, `KC_LSFT` or `KC_RSFT` is passed to
  `caps_word_press_user()` to determine whether to continue.
* When holding a Right Shift + Alt (`RSA_T`) mod-tap, `RSFT(KC_RALT)` is
  passed to `caps_word_press_user()`.

Particularly, with this fix a user may choose to continue Caps Word when
a shift mod-tap key is held by adding `KC_LSFT` and `KC_RSFT` cases in
`caps_word_press_user()`. For instance as

```
bool caps_word_press_user(uint16_t keycode) {
  switch (keycode) {
    // Keycodes that continue Caps Word, with shift applied.
    case KC_A ... KC_Z:
    case KC_MINS:
      add_weak_mods(MOD_BIT(KC_LSFT));  // Apply shift to the next key.
      return true;

    // Keycodes that continue Caps Word, without shifting.
    case KC_1 ... KC_0:
    case KC_BSPC:
    case KC_DEL:
    case KC_UNDS:
    case KC_LSFT:  // <<< Added here.
    case KC_RSFT:
      return true;

    default:
      return false;  // Deactivate Caps Word.
  }
}
```

* Fix Caps Word to treat mod-taps more consistently.

Previously, holding any mod-tap key while Caps Word is active stops Caps
Word, and this happens regardless of `caps_word_press_user()`. Yet for
regular mod keys, AltGr (KC_RALT) is ignored, Shift keys are passed to
`caps_word_press_user()` to determine whether to continue, and
similarly, a key `RSFT(KC_RALT)` representing Right Shift + Alt is
passed to `caps_word_press_user()` to determine whether to continue.

This commit makes held mod-tap keys consistent with regular mod keys:

* Holding a `RALT_T` mod-tap is ignored.
* When holding a shift mod-tap key, `KC_LSFT` or `KC_RSFT` is passed to
  `caps_word_press_user()` to determine whether to continue.
* When holding a Right Shift + Alt (`RSA_T`) mod-tap, `RSFT(KC_RALT)` is
  passed to `caps_word_press_user()`.

Particularly, with this fix a user may choose to continue Caps Word when
a shift mod-tap key is held by adding `KC_LSFT` and `KC_RSFT` cases in
`caps_word_press_user()`. For instance as

```
bool caps_word_press_user(uint16_t keycode) {
  switch (keycode) {
    // Keycodes that continue Caps Word, with shift applied.
    case KC_A ... KC_Z:
    case KC_MINS:
      add_weak_mods(MOD_BIT(KC_LSFT));  // Apply shift to the next key.
      return true;

    // Keycodes that continue Caps Word, without shifting.
    case KC_1 ... KC_0:
    case KC_BSPC:
    case KC_DEL:
    case KC_UNDS:
    case KC_LSFT:  // <<< Added here.
    case KC_RSFT:
      return true;

    default:
      return false;  // Deactivate Caps Word.
  }
}
```

* Update quantum/process_keycode/process_caps_word.c

Co-authored-by: Joel Challis <git@zvecr.com>

1 files changed, 26 insertions, 6 deletions

diff --git a/quantum/process_keycode/process_caps_word.c b/quantum/process_keycode/process_caps_word.c
index bc4369846c..1b9583196d 100644
--- a/quantum/process_keycode/process_caps_word.c
+++ b/quantum/process_keycode/process_caps_word.c
@@ -101,14 +101,34 @@ bool process_caps_word(uint16_t keycode, keyrecord_t* record) {
                 return true;
 
 #ifndef NO_ACTION_TAPPING
+            // Corresponding to mod keys above, a held mod-tap is handled as:
+            // * For shift mods, pass KC_LSFT or KC_RSFT to
+            //   caps_word_press_user() to determine whether to continue.
+            // * For Shift + AltGr (MOD_RSFT | MOD_RALT), pass RSFT(KC_RALT).
+            // * AltGr (MOD_RALT) is ignored.
+            // * Otherwise stop Caps Word.
             case QK_MOD_TAP ... QK_MOD_TAP_MAX:
-                if (record->tap.count == 0) {
-                    // Deactivate if a mod becomes active through holding
-                    // a mod-tap key.
-                    caps_word_off();
-                    return true;
+                if (record->tap.count == 0) { // Mod-tap key is held.
+                    const uint8_t mods = (keycode >> 8) & 0x1f;
+                    switch (mods) {
+                        case MOD_LSFT:
+                            keycode = KC_LSFT;
+                            break;
+                        case MOD_RSFT:
+                            keycode = KC_RSFT;
+                            break;
+                        case MOD_RSFT | MOD_RALT:
+                            keycode = RSFT(KC_RALT);
+                            break;
+                        case MOD_RALT:
+                            return true;
+                        default:
+                            caps_word_off();
+                            return true;
+                    }
+                } else {
+                    keycode &= 0xff;
                 }
-                keycode &= 0xff;
                 break;
 
 #    ifndef NO_ACTION_LAYER