feat(core): Add lv_group_get_obj_by_index method (#6589)

src/core/lv_group.c

@@ -377,6 +377,20 @@ uint32_t lv_group_get_obj_count(lv_group_t * group)
     return lv_ll_get_len(&group->obj_ll);
 }
 
+lv_obj_t * lv_group_get_obj_by_index(lv_group_t * group, uint32_t index)
+{
+    uint32_t len = 0;
+    lv_obj_t ** obj;
+
+    LV_LL_READ(&group->obj_ll, obj) {
+        if(len == index) {
+            return *obj;
+        }
+        len++;
+    }
+    return NULL;
+}
+
 uint32_t lv_group_get_count(void)
 {
     return lv_ll_get_len(group_ll_p);
@@ -385,11 +399,11 @@ uint32_t lv_group_get_count(void)
 lv_group_t  * lv_group_by_index(uint32_t index)
 {
     uint32_t len = 0;
-    void * node;
+    lv_group_t * group;
 
-    for(node = lv_ll_get_tail(group_ll_p); node != NULL; node = lv_ll_get_prev(group_ll_p, node)) {
+    LV_LL_READ_BACK(group_ll_p, group) {
         if(len == index) {
-            return (lv_group_t *) node;
+            return group;
         }
         len++;
     }

src/core/lv_group.h

@@ -213,6 +213,14 @@ bool lv_group_get_wrap(lv_group_t * group);
  */
 uint32_t lv_group_get_obj_count(lv_group_t * group);
 
+/**
+ * Get the nth object within a group
+ * @param group         pointer to a group
+ * @param index         index of object within the group
+ * @return              pointer to the object
+ */
+lv_obj_t * lv_group_get_obj_by_index(lv_group_t * group, uint32_t index);
+
 /**
  * Get the number of groups
  * @return              number of groups
@@ -221,6 +229,7 @@ uint32_t lv_group_get_count(void);
 
 /**
  * Get a group by its index
+ * @param index         index of the group
  * @return              pointer to the group
  */
 lv_group_t  * lv_group_by_index(uint32_t index);

tests/src/test_cases/test_group.c

@@ -39,4 +39,23 @@ void test_group_by_index(void)
     lv_group_delete(group_2);
 }
 
+void test_group_obj_by_index(void)
+{
+    lv_group_t * group = lv_group_create();
+
+    TEST_ASSERT_EQUAL_PTR(lv_group_get_obj_by_index(group, 0), NULL);
+
+    lv_obj_t * obj_0 = lv_obj_create(NULL);
+    lv_obj_t * obj_1 = lv_obj_create(NULL);
+    lv_group_add_obj(group, obj_0);
+    lv_group_add_obj(group, obj_1);
+
+    TEST_ASSERT_EQUAL_PTR(lv_group_get_obj_by_index(group, 0), obj_0);
+    TEST_ASSERT_EQUAL_PTR(lv_group_get_obj_by_index(group, 1), obj_1);
+
+    lv_group_remove_obj(obj_0);
+    TEST_ASSERT_EQUAL_PTR(lv_group_get_obj_by_index(group, 0), obj_1);
+    TEST_ASSERT_EQUAL_PTR(lv_group_get_obj_by_index(group, 1), NULL);
+}
+
 #endif