Refactor events API to avoid heap/dynamic allocations

app/Kconfig

@@ -595,7 +595,7 @@ endmenu
 endmenu
 
 config HEAP_MEM_POOL_SIZE
-    default 8192
+    default 8192 if ZMK_DISPLAY
 
 config KERNEL_BIN_NAME
     default "zmk"

app/include/zmk/event_manager.h

@@ -38,20 +38,23 @@ struct zmk_event_subscription {
         zmk_event_t header;                                                                        \
         struct event_type data;                                                                    \
     };                                                                                             \
-    struct event_type##_event *new_##event_type(struct event_type);                                \
+    struct event_type##_event copy_raised_##event_type(const struct event_type *ev);               \
+    int raise_##event_type(struct event_type);                                                     \
     struct event_type *as_##event_type(const zmk_event_t *eh);                                     \
     extern const struct zmk_event_type zmk_event_##event_type;
 
 #define ZMK_EVENT_IMPL(event_type)                                                                 \
     const struct zmk_event_type zmk_event_##event_type = {.name = STRINGIFY(event_type)};          \
     const struct zmk_event_type *zmk_event_ref_##event_type __used                                 \
         __attribute__((__section__(".event_type"))) = &zmk_event_##event_type;                     \
-    struct event_type##_event *new_##event_type(struct event_type data) {                          \
-        struct event_type##_event *ev =                                                            \
-            (struct event_type##_event *)k_malloc(sizeof(struct event_type##_event));              \
-        ev->header.event = &zmk_event_##event_type;                                                \
-        ev->data = data;                                                                           \
-        return ev;                                                                                 \
+    struct event_type##_event copy_raised_##event_type(const struct event_type *ev) {              \
+        struct event_type##_event *outer = CONTAINER_OF(ev, struct event_type##_event, data);      \
+        return *outer;                                                                             \
+    };                                                                                             \
+    int raise_##event_type(struct event_type data) {                                               \
+        struct event_type##_event ev = {.data = data,                                              \
+                                        .header = {.event = &zmk_event_##event_type}};             \
+        return ZMK_EVENT_RAISE(ev);                                                                \
     };                                                                                             \
     struct event_type *as_##event_type(const zmk_event_t *eh) {                                    \
         return (eh->event == &zmk_event_##event_type) ? &((struct event_type##_event *)eh)->data   \
@@ -68,17 +71,19 @@ struct zmk_event_subscription {
             .listener = &zmk_listener_##mod,                                                       \
     };
 
-#define ZMK_EVENT_RAISE(ev) zmk_event_manager_raise((zmk_event_t *)ev);
+#define ZMK_ASSERT_EVENT_LIKE(ev)                                                                  \
+    (__ASSERT((uint8_t *)&(ev).header - (uint8_t *)&ev == 0,                                       \
+              "header must be first element of event"))
+
+#define ZMK_EVENT_RAISE(ev) (ZMK_ASSERT_EVENT_LIKE(ev), zmk_event_manager_raise(&(ev).header))
 
 #define ZMK_EVENT_RAISE_AFTER(ev, mod)                                                             \
-    zmk_event_manager_raise_after((zmk_event_t *)ev, &zmk_listener_##mod);
+    (ZMK_ASSERT_EVENT_LIKE(ev), zmk_event_manager_raise_after(&(ev).header, &zmk_listener_##mod))
 
 #define ZMK_EVENT_RAISE_AT(ev, mod)                                                                \
-    zmk_event_manager_raise_at((zmk_event_t *)ev, &zmk_listener_##mod);
-
-#define ZMK_EVENT_RELEASE(ev) zmk_event_manager_release((zmk_event_t *)ev);
+    (ZMK_ASSERT_EVENT_LIKE(ev), zmk_event_manager_raise_at(&(ev).header, &zmk_listener_##mod))
 
-#define ZMK_EVENT_FREE(ev) k_free((void *)ev);
+#define ZMK_EVENT_RELEASE(ev) (ZMK_ASSERT_EVENT_LIKE(ev), zmk_event_manager_release(&(ev).header))
 
 int zmk_event_manager_raise(zmk_event_t *event);
 int zmk_event_manager_raise_after(zmk_event_t *event, const struct zmk_listener *listener);

app/include/zmk/events/keycode_state_changed.h

@@ -21,7 +21,7 @@ struct zmk_keycode_state_changed {
 
 ZMK_EVENT_DECLARE(zmk_keycode_state_changed);
 
-static inline struct zmk_keycode_state_changed_event *
+static inline struct zmk_keycode_state_changed
 zmk_keycode_state_changed_from_encoded(uint32_t encoded, bool pressed, int64_t timestamp) {
     uint16_t page = ZMK_HID_USAGE_PAGE(encoded);
     uint16_t id = ZMK_HID_USAGE_ID(encoded);
@@ -38,11 +38,16 @@ zmk_keycode_state_changed_from_encoded(uint32_t encoded, bool pressed, int64_t t
         implicit_modifiers = SELECT_MODS(encoded);
     }
 
-    return new_zmk_keycode_state_changed(
-        (struct zmk_keycode_state_changed){.usage_page = page,
-                                           .keycode = id,
-                                           .implicit_modifiers = implicit_modifiers,
-                                           .explicit_modifiers = explicit_modifiers,
-                                           .state = pressed,
-                                           .timestamp = timestamp});
+    return (struct zmk_keycode_state_changed){.usage_page = page,
+                                              .keycode = id,
+                                              .implicit_modifiers = implicit_modifiers,
+                                              .explicit_modifiers = explicit_modifiers,
+                                              .state = pressed,
+                                              .timestamp = timestamp};
+}
+
+static inline int raise_zmk_keycode_state_changed_from_encoded(uint32_t encoded, bool pressed,
+                                                               int64_t timestamp) {
+    return raise_zmk_keycode_state_changed(
+        zmk_keycode_state_changed_from_encoded(encoded, pressed, timestamp));
 }

app/include/zmk/events/layer_state_changed.h

@@ -17,8 +17,7 @@ struct zmk_layer_state_changed {
 
 ZMK_EVENT_DECLARE(zmk_layer_state_changed);
 
-static inline struct zmk_layer_state_changed_event *create_layer_state_changed(uint8_t layer,
-                                                                               bool state) {
-    return new_zmk_layer_state_changed((struct zmk_layer_state_changed){
+static inline int raise_layer_state_changed(uint8_t layer, bool state) {
+    return raise_zmk_layer_state_changed((struct zmk_layer_state_changed){
         .layer = layer, .state = state, .timestamp = k_uptime_get()});
 }

app/include/zmk/events/mouse_button_state_changed.h

@@ -19,8 +19,8 @@ struct zmk_mouse_button_state_changed {
 
 ZMK_EVENT_DECLARE(zmk_mouse_button_state_changed);
 
-static inline struct zmk_mouse_button_state_changed_event *
-zmk_mouse_button_state_changed_from_encoded(uint32_t encoded, bool pressed, int64_t timestamp) {
-    return new_zmk_mouse_button_state_changed((struct zmk_mouse_button_state_changed){
+static inline int raise_zmk_mouse_button_state_changed_from_encoded(uint32_t encoded, bool pressed,
+                                                                    int64_t timestamp) {
+    return raise_zmk_mouse_button_state_changed((struct zmk_mouse_button_state_changed){
         .buttons = ZMK_HID_USAGE_ID(encoded), .state = pressed, .timestamp = timestamp});
 }

app/src/activity.c

@@ -43,8 +43,8 @@ static uint32_t activity_last_uptime;
 #endif
 
 int raise_event(void) {
-    return ZMK_EVENT_RAISE(new_zmk_activity_state_changed(
-        (struct zmk_activity_state_changed){.state = activity_state}));
+    return raise_zmk_activity_state_changed(
+        (struct zmk_activity_state_changed){.state = activity_state});
 }
 
 int set_state(enum zmk_activity_state state) {

app/src/battery.c

@@ -63,8 +63,8 @@ static int zmk_battery_update(const struct device *battery) {
             return rc;
         }
 #endif
-        rc = ZMK_EVENT_RAISE(new_zmk_battery_state_changed(
-            (struct zmk_battery_state_changed){.state_of_charge = last_state_of_charge}));
+        rc = raise_zmk_battery_state_changed(
+            (struct zmk_battery_state_changed){.state_of_charge = last_state_of_charge});
     }
 
     return rc;

app/src/behaviors/behavior_hold_tap.c

@@ -88,7 +88,24 @@ struct active_hold_tap {
 struct active_hold_tap *undecided_hold_tap = NULL;
 struct active_hold_tap active_hold_taps[ZMK_BHV_HOLD_TAP_MAX_HELD] = {};
 // We capture most position_state_changed events and some modifiers_state_changed events.
-const zmk_event_t *captured_events[ZMK_BHV_HOLD_TAP_MAX_CAPTURED_EVENTS] = {};
+
+enum captured_event_tag {
+    ET_NONE,
+    ET_POS_CHANGED,
+    ET_CODE_CHANGED,
+};
+
+union captured_event_data {
+    struct zmk_position_state_changed_event position;
+    struct zmk_keycode_state_changed_event keycode;
+};
+
+struct captured_event {
+    enum captured_event_tag tag;
+    union captured_event_data data;
+};
+
+struct captured_event captured_events[ZMK_BHV_HOLD_TAP_MAX_CAPTURED_EVENTS] = {};
 
 // Keep track of which key was tapped most recently for the standard, if it is a hold-tap
 // a position, will be given, if not it will just be INT32_MIN
@@ -122,33 +139,32 @@ static bool is_quick_tap(struct active_hold_tap *hold_tap) {
     }
 }
 
-static int capture_event(const zmk_event_t *event) {
+static int capture_event(struct captured_event *data) {
     for (int i = 0; i < ZMK_BHV_HOLD_TAP_MAX_CAPTURED_EVENTS; i++) {
-        if (captured_events[i] == NULL) {
-            captured_events[i] = event;
+        if (captured_events[i].tag == ET_NONE) {
+            captured_events[i] = *data;
             return 0;
         }
     }
     return -ENOMEM;
 }
 
-static struct zmk_position_state_changed *find_captured_keydown_event(uint32_t position) {
-    struct zmk_position_state_changed *last_match = NULL;
+static bool have_captured_keydown_event(uint32_t position) {
     for (int i = 0; i < ZMK_BHV_HOLD_TAP_MAX_CAPTURED_EVENTS; i++) {
-        const zmk_event_t *eh = captured_events[i];
-        if (eh == NULL) {
-            return last_match;
+        struct captured_event *ev = &captured_events[i];
+        if (ev->tag == ET_NONE) {
+            return false;
         }
-        struct zmk_position_state_changed *position_event = as_zmk_position_state_changed(eh);
-        if (position_event == NULL) {
+
+        if (ev->tag != ET_POS_CHANGED) {
             continue;
         }
 
-        if (position_event->position == position && position_event->state) {
-            last_match = position_event;
+        if (ev->data.position.data.position == position && ev->data.position.data.state) {
+            return true;
         }
     }
-    return last_match;
+    return false;
 }
 
 const struct zmk_listener zmk_listener_behavior_hold_tap;
@@ -184,25 +200,35 @@ static void release_captured_events() {
     // [k1_down, k1_up, null, null, null, ...]
     // now mt2 will start releasing it's own captured positions.
     for (int i = 0; i < ZMK_BHV_HOLD_TAP_MAX_CAPTURED_EVENTS; i++) {
-        const zmk_event_t *captured_event = captured_events[i];
-        if (captured_event == NULL) {
+        struct captured_event *captured_event = &captured_events[i];
+        enum captured_event_tag tag = captured_event->tag;
+
+        if (tag == ET_NONE) {
             return;
         }
-        captured_events[i] = NULL;
+
+        captured_events[i].tag = ET_NONE;
         if (undecided_hold_tap != NULL) {
             k_msleep(10);
         }
 
-        struct zmk_position_state_changed *position_event;
-        struct zmk_keycode_state_changed *modifier_event;
-        if ((position_event = as_zmk_position_state_changed(captured_event)) != NULL) {
-            LOG_DBG("Releasing key position event for position %d %s", position_event->position,
-                    (position_event->state ? "pressed" : "released"));
-        } else if ((modifier_event = as_zmk_keycode_state_changed(captured_event)) != NULL) {
-            LOG_DBG("Releasing mods changed event 0x%02X %s", modifier_event->keycode,
-                    (modifier_event->state ? "pressed" : "released"));
+        switch (tag) {
+        case ET_CODE_CHANGED:
+            LOG_DBG("Releasing mods changed event 0x%02X %s",
+                    captured_event->data.keycode.data.keycode,
+                    (captured_event->data.keycode.data.state ? "pressed" : "released"));
+            ZMK_EVENT_RAISE_AT(captured_event->data.keycode, behavior_hold_tap);
+            break;
+        case ET_POS_CHANGED:
+            LOG_DBG("Releasing key position event for position %d %s",
+                    captured_event->data.position.data.position,
+                    (captured_event->data.position.data.state ? "pressed" : "released"));
+            ZMK_EVENT_RAISE_AT(captured_event->data.position, behavior_hold_tap);
+            break;
+        default:
+            LOG_ERR("Unhandled captured event type");
+            break;
         }
-        ZMK_EVENT_RAISE_AT(captured_event, behavior_hold_tap);
     }
 }
 
@@ -622,7 +648,7 @@ static int position_state_changed_listener(const zmk_event_t *eh) {
         return ZMK_EV_EVENT_BUBBLE;
     }
 
-    if (!ev->state && find_captured_keydown_event(ev->position) == NULL) {
+    if (!ev->state && !have_captured_keydown_event(ev->position)) {
         // no keydown event has been captured, let it bubble.
         // we'll catch modifiers later in modifier_state_changed_listener
         LOG_DBG("%d bubbling %d %s event", undecided_hold_tap->position, ev->position,
@@ -632,7 +658,11 @@ static int position_state_changed_listener(const zmk_event_t *eh) {
 
     LOG_DBG("%d capturing %d %s event", undecided_hold_tap->position, ev->position,
             ev->state ? "down" : "up");
-    capture_event(eh);
+    struct captured_event capture = {
+        .tag = ET_POS_CHANGED,
+        .data = {.position = copy_raised_zmk_position_state_changed(ev)},
+    };
+    capture_event(&capture);
     decide_hold_tap(undecided_hold_tap, ev->state ? HT_OTHER_KEY_DOWN : HT_OTHER_KEY_UP);
     return ZMK_EV_EVENT_CAPTURED;
 }
@@ -659,7 +689,9 @@ static int keycode_state_changed_listener(const zmk_event_t *eh) {
     // if a undecided_hold_tap is active.
     LOG_DBG("%d capturing 0x%02X %s event", undecided_hold_tap->position, ev->keycode,
             ev->state ? "down" : "up");
-    capture_event(eh);
+    struct captured_event capture = {
+        .tag = ET_CODE_CHANGED, .data = {.keycode = copy_raised_zmk_keycode_state_changed(ev)}};
+    capture_event(&capture);
     return ZMK_EV_EVENT_CAPTURED;
 }
 

app/src/behaviors/behavior_key_press.c

@@ -21,15 +21,13 @@ static int behavior_key_press_init(const struct device *dev) { return 0; };
 static int on_keymap_binding_pressed(struct zmk_behavior_binding *binding,
                                      struct zmk_behavior_binding_event event) {
     LOG_DBG("position %d keycode 0x%02X", event.position, binding->param1);
-    return ZMK_EVENT_RAISE(
-        zmk_keycode_state_changed_from_encoded(binding->param1, true, event.timestamp));
+    return raise_zmk_keycode_state_changed_from_encoded(binding->param1, true, event.timestamp);
 }
 
 static int on_keymap_binding_released(struct zmk_behavior_binding *binding,
                                       struct zmk_behavior_binding_event event) {
     LOG_DBG("position %d keycode 0x%02X", event.position, binding->param1);
-    return ZMK_EVENT_RAISE(
-        zmk_keycode_state_changed_from_encoded(binding->param1, false, event.timestamp));
+    return raise_zmk_keycode_state_changed_from_encoded(binding->param1, false, event.timestamp);
 }
 
 static const struct behavior_driver_api behavior_key_press_driver_api = {

app/src/behaviors/behavior_key_repeat.c

@@ -43,7 +43,7 @@ static int on_key_repeat_binding_pressed(struct zmk_behavior_binding *binding,
            sizeof(struct zmk_keycode_state_changed));
     data->current_keycode_pressed.timestamp = k_uptime_get();
 
-    ZMK_EVENT_RAISE(new_zmk_keycode_state_changed(data->current_keycode_pressed));
+    raise_zmk_keycode_state_changed(data->current_keycode_pressed);
 
     return ZMK_BEHAVIOR_OPAQUE;
 }
@@ -60,7 +60,7 @@ static int on_key_repeat_binding_released(struct zmk_behavior_binding *binding,
     data->current_keycode_pressed.timestamp = k_uptime_get();
     data->current_keycode_pressed.state = false;
 
-    ZMK_EVENT_RAISE(new_zmk_keycode_state_changed(data->current_keycode_pressed));
+    raise_zmk_keycode_state_changed(data->current_keycode_pressed);
     return ZMK_BEHAVIOR_OPAQUE;
 }
 

app/src/behaviors/behavior_key_toggle.c

@@ -23,8 +23,7 @@ static int on_keymap_binding_pressed(struct zmk_behavior_binding *binding,
                                      struct zmk_behavior_binding_event event) {
     LOG_DBG("position %d keycode 0x%02X", event.position, binding->param1);
     bool pressed = zmk_hid_is_pressed(binding->param1);
-    return ZMK_EVENT_RAISE(
-        zmk_keycode_state_changed_from_encoded(binding->param1, !pressed, event.timestamp));
+    return raise_zmk_keycode_state_changed_from_encoded(binding->param1, !pressed, event.timestamp);
 }
 
 static int on_keymap_binding_released(struct zmk_behavior_binding *binding,

app/src/behaviors/behavior_mouse_key_press.c

@@ -24,15 +24,15 @@ static int on_keymap_binding_pressed(struct zmk_behavior_binding *binding,
                                      struct zmk_behavior_binding_event event) {
     LOG_DBG("position %d keycode 0x%02X", event.position, binding->param1);
 
-    return ZMK_EVENT_RAISE(
-        zmk_mouse_button_state_changed_from_encoded(binding->param1, true, event.timestamp));
+    return raise_zmk_mouse_button_state_changed_from_encoded(binding->param1, true,
+                                                             event.timestamp);
 }
 
 static int on_keymap_binding_released(struct zmk_behavior_binding *binding,
                                       struct zmk_behavior_binding_event event) {
     LOG_DBG("position %d keycode 0x%02X", event.position, binding->param1);
-    return ZMK_EVENT_RAISE(
-        zmk_mouse_button_state_changed_from_encoded(binding->param1, false, event.timestamp));
+    return raise_zmk_mouse_button_state_changed_from_encoded(binding->param1, false,
+                                                             event.timestamp);
 }
 
 static const struct behavior_driver_api behavior_mouse_key_press_driver_api = {

app/src/behaviors/behavior_sticky_key.c

@@ -236,7 +236,9 @@ static int sticky_key_keycode_state_changed_listener(const zmk_event_t *eh) {
                 if (sticky_key->config->quick_release) {
                     // immediately release the sticky key after the key press is handled.
                     if (!event_reraised) {
-                        ZMK_EVENT_RAISE_AFTER(eh, behavior_sticky_key);
+                        struct zmk_keycode_state_changed_event dupe_ev =
+                            copy_raised_zmk_keycode_state_changed(ev);
+                        ZMK_EVENT_RAISE_AFTER(dupe_ev, behavior_sticky_key);
                         event_reraised = true;
                     }
                     release_sticky_key_behavior(sticky_key, ev_copy.timestamp);

app/src/ble.c

@@ -83,8 +83,8 @@ static bt_addr_le_t peripheral_addrs[ZMK_SPLIT_BLE_PERIPHERAL_COUNT];
 #endif /* IS_ENABLED(CONFIG_ZMK_SPLIT_ROLE_CENTRAL) */
 
 static void raise_profile_changed_event(void) {
-    ZMK_EVENT_RAISE(new_zmk_ble_active_profile_changed((struct zmk_ble_active_profile_changed){
-        .index = active_profile, .profile = &profiles[active_profile]}));
+    raise_zmk_ble_active_profile_changed((struct zmk_ble_active_profile_changed){
+        .index = active_profile, .profile = &profiles[active_profile]});
 }
 
 static void raise_profile_changed_event_callback(struct k_work *work) {