feat(obj) add lv_obj_del_delayed()

docs/overview/object.md

@@ -121,6 +121,8 @@ This is useful e.g. if you want to delete the parent of an object in the child's
 
 You can remove all the children of an object (but not the object itself) using `lv_obj_clean(obj)`.
 
+You can use `lv_obj_del_delayed(obj, 1000)` to delete an object after some time. The delay is expressed in millliseconds. 
+
 
 ## Screens
 

src/core/lv_obj_tree.c

@@ -106,6 +106,18 @@ void lv_obj_clean(lv_obj_t * obj)
     LV_LOG_TRACE("finished (delete %p)", obj)
 }
 
+void lv_obj_del_delayed(lv_obj_t * obj, uint32_t delay_ms)
+{
+    lv_anim_t a;
+    lv_anim_init(&a);
+    lv_anim_set_var(&a, obj);
+    lv_anim_set_exec_cb(&a, NULL);
+    lv_anim_set_time(&a, 1);
+    lv_anim_set_delay(&a, delay_ms);
+    lv_anim_set_ready_cb(&a, lv_obj_del_anim_ready_cb);
+    lv_anim_start(&a);
+}
+
 void lv_obj_del_anim_ready_cb(lv_anim_t * a)
 {
     lv_obj_del(a->var);

src/core/lv_obj_tree.h

@@ -56,6 +56,13 @@ void lv_obj_del(struct _lv_obj_t * obj);
  */
 void lv_obj_clean(struct _lv_obj_t * obj);
 
+/**
+ * Delete an object after some delay
+ * @param obj       pointer to an object
+ * @param delay_ms  time to wait before delete in milliseconds
+ */
+void lv_obj_del_delayed(struct _lv_obj_t * obj, uint32_t delay_ms);
+
 /**
  * A function to be easily used in animation ready callback to delete an object when the animation is ready
  * @param a         pointer to the animation