fix(hid): Implicit mods on non-key page events

* Properly send the KEY usage page report for modifier changes
  when there are state changes to other usages pages that
  include implicit modifiers.

app/src/hid.c

@@ -26,14 +26,17 @@ static zmk_mod_flags_t explicit_modifiers = 0;
         LOG_DBG("Modifiers set to 0x%02X", keyboard_report.body.modifiers);                        \
     }
 
+#define GET_MODIFIERS (keyboard_report.body.modifiers)
+
 zmk_mod_flags_t zmk_hid_get_explicit_mods() { return explicit_modifiers; }
 
 int zmk_hid_register_mod(zmk_mod_t modifier) {
     explicit_modifier_counts[modifier]++;
     LOG_DBG("Modifier %d count %d", modifier, explicit_modifier_counts[modifier]);
     WRITE_BIT(explicit_modifiers, modifier, true);
+    zmk_mod_flags_t current = GET_MODIFIERS;
     SET_MODIFIERS(explicit_modifiers);
-    return 0;
+    return current == GET_MODIFIERS ? 0 : 1;
 }
 
 int zmk_hid_unregister_mod(zmk_mod_t modifier) {
@@ -47,26 +50,30 @@ int zmk_hid_unregister_mod(zmk_mod_t modifier) {
         LOG_DBG("Modifier %d released", modifier);
         WRITE_BIT(explicit_modifiers, modifier, false);
     }
+    zmk_mod_flags_t current = GET_MODIFIERS;
     SET_MODIFIERS(explicit_modifiers);
-    return 0;
+    return current == GET_MODIFIERS ? 0 : 1;
 }
 
 int zmk_hid_register_mods(zmk_mod_flags_t modifiers) {
+    int ret = 0;
     for (zmk_mod_t i = 0; i < 8; i++) {
         if (modifiers & (1 << i)) {
-            zmk_hid_register_mod(i);
+            ret += zmk_hid_register_mod(i);
         }
     }
-    return 0;
+    return ret;
 }
 
 int zmk_hid_unregister_mods(zmk_mod_flags_t modifiers) {
+    int ret = 0;
     for (zmk_mod_t i = 0; i < 8; i++) {
         if (modifiers & (1 << i)) {
-            zmk_hid_unregister_mod(i);
+            ret += zmk_hid_unregister_mod(i);
         }
     }
-    return 0;
+
+    return ret;
 }
 
 #if IS_ENABLED(CONFIG_ZMK_HID_REPORT_TYPE_NKRO)
@@ -130,13 +137,15 @@ static inline int deselect_keyboard_usage(zmk_key_t usage) {
     }
 
 int zmk_hid_implicit_modifiers_press(zmk_mod_flags_t implicit_modifiers) {
+    zmk_mod_flags_t current = GET_MODIFIERS;
     SET_MODIFIERS(explicit_modifiers | implicit_modifiers);
-    return 0;
+    return current == GET_MODIFIERS ? 0 : 1;
 }
 
 int zmk_hid_implicit_modifiers_release() {
+    zmk_mod_flags_t current = GET_MODIFIERS;
     SET_MODIFIERS(explicit_modifiers);
-    return 0;
+    return current == GET_MODIFIERS ? 0 : 1;
 }
 
 int zmk_hid_keyboard_press(zmk_key_t code) {

app/src/hid_listener.c

@@ -17,56 +17,77 @@ LOG_MODULE_DECLARE(zmk, CONFIG_ZMK_LOG_LEVEL);
 #include <zmk/endpoints.h>
 
 static int hid_listener_keycode_pressed(const struct zmk_keycode_state_changed *ev) {
-    int err;
+    int err, explicit_mods_changed, implicit_mods_changed;
+
     LOG_DBG("usage_page 0x%02X keycode 0x%02X implicit_mods 0x%02X explicit_mods 0x%02X",
             ev->usage_page, ev->keycode, ev->implicit_modifiers, ev->explicit_modifiers);
     switch (ev->usage_page) {
     case HID_USAGE_KEY:
         err = zmk_hid_keyboard_press(ev->keycode);
-        if (err) {
+        if (err < 0) {
             LOG_ERR("Unable to press keycode");
             return err;
         }
         break;
     case HID_USAGE_CONSUMER:
         err = zmk_hid_consumer_press(ev->keycode);
-        if (err) {
+        if (err < 0) {
             LOG_ERR("Unable to press keycode");
             return err;
         }
         break;
     }
-    zmk_hid_register_mods(ev->explicit_modifiers);
-    zmk_hid_implicit_modifiers_press(ev->implicit_modifiers);
+    explicit_mods_changed = zmk_hid_register_mods(ev->explicit_modifiers);
+    implicit_mods_changed = zmk_hid_implicit_modifiers_press(ev->implicit_modifiers);
+    if (ev->usage_page != HID_USAGE_KEY &&
+        (explicit_mods_changed > 0 || implicit_mods_changed > 0)) {
+        err = zmk_endpoints_send_report(HID_USAGE_KEY);
+        if (err < 0) {
+            LOG_ERR("Failed to send key report for changed mofifiers for consumer page event (%d)",
+                    err);
+        }
+    }
+
     return zmk_endpoints_send_report(ev->usage_page);
 }
 
 static int hid_listener_keycode_released(const struct zmk_keycode_state_changed *ev) {
-    int err;
+    int err, explicit_mods_changed, implicit_mods_changed;
+
     LOG_DBG("usage_page 0x%02X keycode 0x%02X implicit_mods 0x%02X explicit_mods 0x%02X",
             ev->usage_page, ev->keycode, ev->implicit_modifiers, ev->explicit_modifiers);
     switch (ev->usage_page) {
     case HID_USAGE_KEY:
         err = zmk_hid_keyboard_release(ev->keycode);
-        if (err) {
+        if (err < 0) {
             LOG_ERR("Unable to release keycode");
             return err;
         }
         break;
     case HID_USAGE_CONSUMER:
         err = zmk_hid_consumer_release(ev->keycode);
-        if (err) {
+        if (err < 0) {
             LOG_ERR("Unable to release keycode");
             return err;
         }
     }
-    zmk_hid_unregister_mods(ev->explicit_modifiers);
+
+    explicit_mods_changed = zmk_hid_unregister_mods(ev->explicit_modifiers);
     // There is a minor issue with this code.
     // If LC(A) is pressed, then LS(B), then LC(A) is released, the shift for B will be released
     // prematurely. This causes if LS(B) to repeat like Bbbbbbbb when pressed for a long time.
     // Solving this would require keeping track of which key's implicit modifiers are currently
     // active and only releasing modifiers at that time.
-    zmk_hid_implicit_modifiers_release();
+    implicit_mods_changed = zmk_hid_implicit_modifiers_release();
+    ;
+    if (ev->usage_page != HID_USAGE_KEY &&
+        (explicit_mods_changed > 0 || implicit_mods_changed > 0)) {
+        err = zmk_endpoints_send_report(HID_USAGE_KEY);
+        if (err < 0) {
+            LOG_ERR("Failed to send key report for changed mofifiers for consumer page event (%d)",
+                    err);
+        }
+    }
     return zmk_endpoints_send_report(ev->usage_page);
 }