feat(events): add event trickle mechanism to propagate events to children (#8415)

Co-authored-by: Gauthier Provost <gpr@interel.com>

tests/src/test_cases/test_event_trickle.c

@@ -0,0 +1,96 @@
+#if LV_BUILD_TEST
+#include "../lvgl.h"
+#include "../../lvgl_private.h"
+
+#include "unity/unity.h"
+
+static uint32_t event_count = 0;
+static lv_obj_t * last_target = NULL;
+
+static void test_event_cb(lv_event_t * e)
+{
+    event_count++;
+    last_target = lv_event_get_current_target_obj(e);
+}
+
+void test_event_trickle_basic(void)
+{
+    /*Create a parent container*/
+    lv_obj_t * parent = lv_obj_create(lv_screen_active());
+    lv_obj_add_flag(parent, LV_OBJ_FLAG_EVENT_TRICKLE);
+    lv_obj_add_event_cb(parent, test_event_cb, LV_EVENT_CLICKED, NULL);
+
+    /*Create children*/
+    lv_obj_t * child1 = lv_obj_create(parent);
+    lv_obj_add_event_cb(child1, test_event_cb, LV_EVENT_CLICKED, NULL);
+
+    lv_obj_t * child2 = lv_obj_create(parent);
+    lv_obj_add_event_cb(child2, test_event_cb, LV_EVENT_CLICKED, NULL);
+
+    /*Reset counters*/
+    event_count = 0;
+    last_target = NULL;
+
+    /*Send event to parent - should trickle down to children*/
+    lv_obj_send_event(parent, LV_EVENT_CLICKED, NULL);
+
+    /*Should have received 3 events: parent + 2 children*/
+    TEST_ASSERT_EQUAL(3, event_count);
+
+    /*Clean up*/
+    lv_obj_delete(parent);
+}
+
+void test_event_trickle_stop(void)
+{
+    /*Create a parent container*/
+    lv_obj_t * parent = lv_obj_create(lv_screen_active());
+    lv_obj_add_flag(parent, LV_OBJ_FLAG_EVENT_TRICKLE);
+
+    /*Add event handler that stops trickle down*/
+    lv_obj_add_event_cb(parent, test_event_cb, LV_EVENT_CLICKED, NULL);
+    lv_obj_add_event_cb(parent, (lv_event_cb_t)lv_event_stop_trickling, LV_EVENT_CLICKED, NULL);
+
+    /*Create children*/
+    lv_obj_t * child1 = lv_obj_create(parent);
+    lv_obj_add_event_cb(child1, test_event_cb, LV_EVENT_CLICKED, NULL);
+
+    /*Reset counters*/
+    event_count = 0;
+    last_target = NULL;
+
+    /*Send event to parent - should NOT trickle down due to stop*/
+    lv_obj_send_event(parent, LV_EVENT_CLICKED, NULL);
+
+    /*Should have received only 1 event: parent only*/
+    TEST_ASSERT_EQUAL(1, event_count); /* parent event handler + stop handler */
+
+    /*Clean up*/
+    lv_obj_delete(parent);
+}
+
+void test_event_trickle_disabled(void)
+{
+    /*Create a parent container WITHOUT trickle down flag*/
+    lv_obj_t * parent = lv_obj_create(lv_screen_active());
+    lv_obj_add_event_cb(parent, test_event_cb, LV_EVENT_CLICKED, NULL);
+
+    /*Create children*/
+    lv_obj_t * child1 = lv_obj_create(parent);
+    lv_obj_add_event_cb(child1, test_event_cb, LV_EVENT_CLICKED, NULL);
+
+    /*Reset counters*/
+    event_count = 0;
+    last_target = NULL;
+
+    /*Send event to parent - should NOT trickle down*/
+    lv_obj_send_event(parent, LV_EVENT_CLICKED, NULL);
+
+    /*Should have received only 1 event: parent only*/
+    TEST_ASSERT_EQUAL(1, event_count);
+
+    /*Clean up*/
+    lv_obj_delete(parent);
+}
+
+#endif