feat(event) add LV_EVENT_CHILD_CREATED/DELETED (#2618)

* feat(event) add LV_EVENT_CHILD_CREATED/DELETED

* update docs and CHANGELOG

docs/CHANGELOG.md

@@ -38,6 +38,7 @@
 - fix(disp) set default theme also for non-default displays
 - feat(btnmatrix/keyboard): add option to show popovers on button press
 - fix(types) LV_FORMAT_ATTRIBUTE now works with gnu version greater than 4.4
+- feat(event) add add LV_EVENT_CHILD_CREATED/DELETED
 
 ## v8.0.2 (16.07.2021)
 - fix(theme) improve button focus of keyboard

docs/overview/event.md

@@ -104,6 +104,8 @@ The following event codes exist:
 ### Other events
 - `LV_EVENT_DELETE`       Object is being deleted
 - `LV_EVENT_CHILD_CHANGED`    Child was removed/added
+- `LV_EVENT_CHILD_CREATED`    Child was created, always bubbles up to all parents
+- `LV_EVENT_CHILD_DELETED`    Child was deleted, always bubbles up to all parents
 - `LV_EVENT_SIZE_CHANGED`    Object coordinates/size have changed
 - `LV_EVENT_STYLE_CHANGED`    Object's style has changed
 - `LV_EVENT_BASE_DIR_CHANGED` The base dir has changed

src/core/lv_event.c

@@ -28,7 +28,8 @@ typedef struct _lv_event_dsc_t {
  **********************/
 static lv_event_dsc_t * lv_obj_get_event_dsc(const lv_obj_t * obj, uint32_t id);
 static lv_res_t event_send_core(lv_event_t * e);
-static bool event_is_bubbled(lv_event_code_t e);
+static bool event_is_bubbled(lv_event_t * e);
+
 
 /**********************
  *  STATIC VARIABLES
@@ -427,20 +428,32 @@ static lv_res_t event_send_core(lv_event_t * e)
         event_dsc = lv_obj_get_event_dsc(e->current_target, i);
     }
 
-    if(res == LV_RES_OK && event_is_bubbled(e->code)) {
-        if(lv_obj_has_flag(e->current_target, LV_OBJ_FLAG_EVENT_BUBBLE) && e->current_target->parent) {
+    if(res == LV_RES_OK && e->current_target->parent && event_is_bubbled(e))
+    {
             e->current_target = e->current_target->parent;
             res = event_send_core(e);
             if(res != LV_RES_OK) return LV_RES_INV;
-        }
+
     }
 
     return res;
 }
 
-static bool event_is_bubbled(lv_event_code_t e)
+static bool event_is_bubbled(lv_event_t * e)
 {
-    switch(e) {
+    /*Event codes that always bubble*/
+    switch(e->code) {
+        case LV_EVENT_CHILD_CREATED:
+        case LV_EVENT_CHILD_DELETED:
+            return true;
+        default:
+            break;
+    }
+
+    /*Check other codes only if bubbling is enabled*/
+    if(lv_obj_has_flag(e->current_target, LV_OBJ_FLAG_EVENT_BUBBLE) == false) return false;
+
+    switch(e->code) {
         case LV_EVENT_HIT_TEST:
         case LV_EVENT_COVER_CHECK:
         case LV_EVENT_REFR_EXT_DRAW_SIZE:
@@ -454,6 +467,8 @@ static bool event_is_bubbled(lv_event_code_t e)
         case LV_EVENT_DRAW_PART_END:
         case LV_EVENT_REFRESH:
         case LV_EVENT_DELETE:
+        case LV_EVENT_CHILD_CREATED:
+        case LV_EVENT_CHILD_DELETED:
         case LV_EVENT_CHILD_CHANGED:
         case LV_EVENT_SIZE_CHANGED:
         case LV_EVENT_STYLE_CHANGED:

src/core/lv_event.h

@@ -72,7 +72,9 @@ typedef enum {
 
     /** Other events*/
     LV_EVENT_DELETE,              /**< Object is being deleted*/
-    LV_EVENT_CHILD_CHANGED,       /**< Child was removed/added*/
+    LV_EVENT_CHILD_CHANGED,       /**< Child was removed, added, or its size, position were changed */
+    LV_EVENT_CHILD_CREATED,       /**< Child was created, always bubbles up to all parents*/
+    LV_EVENT_CHILD_DELETED,       /**< Child was deleted, always bubbles up to all parents*/
     LV_EVENT_SIZE_CHANGED,        /**< Object coordinates/size have changed*/
     LV_EVENT_STYLE_CHANGED,       /**< Object's style has changed*/
     LV_EVENT_LAYOUT_CHANGED,      /**< The children position has changed due to a layout recalculation*/

src/core/lv_obj_class.c

@@ -123,6 +123,7 @@ void lv_obj_class_init_obj(lv_obj_t * obj)
         /*Call the ancestor's event handler to the parent to notify it about the new child.
          *Also triggers layout update*/
         lv_event_send(parent, LV_EVENT_CHILD_CHANGED, obj);
+        lv_event_send(parent, LV_EVENT_CHILD_CREATED, obj);
 
         /*Invalidate the area if not screen created*/
         lv_obj_invalidate(obj);

src/core/lv_obj_tree.c

@@ -72,6 +72,7 @@ void lv_obj_del(lv_obj_t * obj)
         lv_obj_readjust_scroll(par, LV_ANIM_OFF);
         lv_obj_scrollbar_invalidate(par);
         lv_event_send(par, LV_EVENT_CHILD_CHANGED, NULL);
+        lv_event_send(par, LV_EVENT_CHILD_DELETED, NULL);
     }
 
     /*Handle if the active screen was deleted*/
@@ -193,9 +194,11 @@ void lv_obj_set_parent(lv_obj_t * obj, lv_obj_t * parent)
 
     /*Notify the original parent because one of its children is lost*/
     lv_event_send(old_parent, LV_EVENT_CHILD_CHANGED, obj);
+    lv_event_send(old_parent, LV_EVENT_CHILD_DELETED, NULL);
 
     /*Notify the new parent about the child*/
     lv_event_send(parent, LV_EVENT_CHILD_CHANGED, obj);
+    lv_event_send(parent, LV_EVENT_CHILD_CREATED, NULL);
 
     lv_obj_invalidate(obj);
 }
@@ -242,11 +245,16 @@ void lv_obj_swap(lv_obj_t * obj1, lv_obj_t * obj2)
     uint_fast32_t index1 = lv_obj_get_index(obj1);
     uint_fast32_t index2 = lv_obj_get_index(obj2);
 
+    lv_event_send(parent2, LV_EVENT_CHILD_DELETED, obj2);
+    lv_event_send(parent, LV_EVENT_CHILD_DELETED, obj1);
+
     parent->spec_attr->children[index1] = obj2;
     parent2->spec_attr->children[index2] = obj1;
 
     lv_event_send(parent, LV_EVENT_CHILD_CHANGED, obj2);
+    lv_event_send(parent, LV_EVENT_CHILD_CREATED, obj2);
     lv_event_send(parent2, LV_EVENT_CHILD_CHANGED, obj1);
+    lv_event_send(parent2, LV_EVENT_CHILD_CREATED, obj1);
 
     lv_obj_invalidate(parent);