fix(obj) swap objects in the group too in lv_obj_swap()

fix #2462

src/core/lv_group.c

@@ -139,6 +139,21 @@ void lv_group_add_obj(lv_group_t * group, lv_obj_t * obj)
     LV_LOG_TRACE("finished");
 }
 
+void lv_group_swap_obj(lv_obj_t * obj1, lv_obj_t * obj2)
+{
+    lv_group_t * g1 = lv_obj_get_group(obj1);
+    lv_group_t * g2 = lv_obj_get_group(obj2);
+    if(g1 != g2) return;
+    if(g1 == NULL) return;
+
+    /*Do not add the object twice*/
+    lv_obj_t ** obj_i;
+    _LV_LL_READ(&g1->obj_ll, obj_i) {
+        if((*obj_i) == obj1) (*obj_i) =  obj2;
+        else if((*obj_i) == obj2) (*obj_i) =  obj1;
+    }
+}
+
 void lv_group_remove_obj(lv_obj_t * obj)
 {
     lv_group_t * g = lv_obj_get_group(obj);

src/core/lv_group.h

@@ -119,6 +119,13 @@ lv_group_t * lv_group_get_default(void);
  */
 void lv_group_add_obj(lv_group_t * group, struct _lv_obj_t * obj);
 
+/**
+ * Swap 2 object in a group. The object must be in the same group
+ * @param obj1  pointer to an object
+ * @param obj2  pointer to an other object
+ */
+void lv_group_swap_obj(struct _lv_obj_t * obj1, struct _lv_obj_t * obj2);
+
 /**
  * Remove an object from its group
  * @param obj       pointer to an object to remove

src/core/lv_obj_tree.c

@@ -253,10 +253,11 @@ void lv_obj_swap(lv_obj_t * obj1, lv_obj_t * obj2)
     lv_event_send(parent2, LV_EVENT_CHILD_CHANGED, obj1);
 
     lv_obj_invalidate(parent);
-    if( parent != parent2)
+    if( parent != parent2) {
-    {
         lv_obj_invalidate(parent2);
     }
+
+    lv_group_swap_obj(obj1, obj2);
 }
 
 lv_obj_t * lv_obj_get_screen(const lv_obj_t * obj)