[Core] Caps Word "Invert on shift" option: pressing Shift inverts the shift state. (#20092)

Co-authored-by: Nick Brassel <nick@tzarc.org>

1 files changed, 66 insertions, 0 deletions

diff --git a/quantum/process_keycode/process_caps_word.c b/quantum/process_keycode/process_caps_word.c
index 94302b29ae..8f2ee1db8b 100644
--- a/quantum/process_keycode/process_caps_word.c
+++ b/quantum/process_keycode/process_caps_word.c
@@ -14,6 +14,54 @@
 
 #include "process_caps_word.h"
 
+#ifdef CAPS_WORD_INVERT_ON_SHIFT
+static uint8_t held_mods = 0;
+
+static bool handle_shift(uint16_t keycode, keyrecord_t* record) {
+    switch (keycode) {
+        case OSM(MOD_LSFT):
+            keycode = KC_LSFT;
+            break;
+        case OSM(MOD_RSFT):
+            keycode = KC_RSFT;
+            break;
+
+#    ifndef NO_ACTION_TAPPING
+        case QK_MOD_TAP ... QK_MOD_TAP_MAX:
+            if (record->tap.count == 0) { // Mod-tap key is held.
+                switch (QK_MOD_TAP_GET_MODS(keycode)) {
+                    case MOD_LSFT:
+                        keycode = KC_LSFT;
+                        break;
+                    case MOD_RSFT:
+                        keycode = KC_RSFT;
+                        break;
+                }
+            }
+#    endif // NO_ACTION_TAPPING
+    }
+
+    if (keycode == KC_LSFT || keycode == KC_RSFT) {
+        const uint8_t mod = MOD_BIT(keycode);
+
+        if (is_caps_word_on()) {
+            if (record->event.pressed) {
+                held_mods |= mod;
+            } else {
+                held_mods &= ~mod;
+            }
+            return false;
+        } else if ((held_mods & mod) != 0) {
+            held_mods &= ~mod;
+            del_mods(mod);
+            return record->event.pressed;
+        }
+    }
+
+    return true;
+}
+#endif // CAPS_WORD_INVERT_ON_SHIFT
+
 bool process_caps_word(uint16_t keycode, keyrecord_t* record) {
     if (keycode == QK_CAPS_WORD_TOGGLE) {
         if (record->event.pressed) {
@@ -21,6 +69,11 @@ bool process_caps_word(uint16_t keycode, keyrecord_t* record) {
         }
         return false;
     }
+#ifdef CAPS_WORD_INVERT_ON_SHIFT
+    if (!handle_shift(keycode, record)) {
+        return false;
+    }
+#endif // CAPS_WORD_INVERT_ON_SHIFT
 
 #ifndef NO_ACTION_ONESHOT
     const uint8_t mods = get_mods() | get_oneshot_mods();
@@ -111,12 +164,14 @@ bool process_caps_word(uint16_t keycode, keyrecord_t* record) {
                 if (record->tap.count == 0) { // Mod-tap key is held.
                     const uint8_t mods = QK_MOD_TAP_GET_MODS(keycode);
                     switch (mods) {
+#    ifndef CAPS_WORD_INVERT_ON_SHIFT
                         case MOD_LSFT:
                             keycode = KC_LSFT;
                             break;
                         case MOD_RSFT:
                             keycode = KC_RSFT;
                             break;
+#    endif // CAPS_WORD_INVERT_ON_SHIFT
                         case MOD_RSFT | MOD_RALT:
                             keycode = RSFT(KC_RALT);
                             break;
@@ -124,6 +179,9 @@ bool process_caps_word(uint16_t keycode, keyrecord_t* record) {
                             return true;
                         default:
                             caps_word_off();
+#    ifdef CAPS_WORD_INVERT_ON_SHIFT
+                            add_mods(held_mods);
+#    endif // CAPS_WORD_INVERT_ON_SHIFT
                             return true;
                     }
                 } else {
@@ -163,12 +221,20 @@ bool process_caps_word(uint16_t keycode, keyrecord_t* record) {
         clear_weak_mods();
 #endif // AUTO_SHIFT_ENABLE
         if (caps_word_press_user(keycode)) {
+#ifdef CAPS_WORD_INVERT_ON_SHIFT
+            if (held_mods) {
+                set_weak_mods(get_weak_mods() ^ MOD_BIT(KC_LSFT));
+            }
+#endif // CAPS_WORD_INVERT_ON_SHIFT
             send_keyboard_report();
             return true;
         }
     }
 
     caps_word_off();
+#ifdef CAPS_WORD_INVERT_ON_SHIFT
+    add_mods(held_mods);
+#endif // CAPS_WORD_INVERT_ON_SHIFT
     return true;
 }