# lv_obj_private.h (/api/core/lv_obj_private_h)
Functions [#functions]
lv_obj_allocate_spec_attr [#lv_obj_allocate_spec_attr]
Allocate special data for an object if not allocated yet.
```c title=" " lineNumbers=1
lv_obj_spec_attr_t * lv_obj_allocate_spec_attr(lv_obj_t *obj)
```
Parameters
| Name | Type | Description |
| ----- | ------------------------------------------------ | -------------------- |
| `obj` | | pointer to an object |
**Returns:** — the spec\_attr created or NULL if something went wrong
lv_obj_add_child [#lv_obj_add_child]
```c title=" " lineNumbers=1
lv_result_t lv_obj_add_child(lv_obj_t *parent, lv_obj_t *child)
```
Parameters
| Name | Type |
| -------- | ------------------------------------------------ |
| `parent` | |
| `child` | |
lv_obj_remove_child [#lv_obj_remove_child]
```c title=" " lineNumbers=1
void lv_obj_remove_child(lv_obj_t *parent, lv_obj_t *child)
```
Parameters
| Name | Type |
| -------- | ------------------------------------------------ |
| `parent` | |
| `child` | |
Structs [#structs]
\_lv_obj_spec_attr_t [#_lv_obj_spec_attr_t]
Special, rarely used attributes. They are allocated automatically if any elements is set.
| Member | Type | Description |
| ---------------- | ---------------------------------------------------- | -------------------------------------------------------------------------- |
| `children` | | Store the pointer of the children in an array. |
| `group_p` | | |
| `event_list` | | |
| `name` | `const char *` | Pointer to the name |
| `scroll` | | The current X/Y scroll offset |
| `ext_click_pad` | | Extra click padding in all direction |
| `ext_draw_size` | | EXTend the size in every direction for drawing. |
| `child_cnt` | | Number of children |
| `scrollbar_mode` | | How to display scrollbars, see `lv_scrollbar_mode_t` |
| `scroll_snap_x` | | Where to align the snappable children horizontally, see `lv_scroll_snap_t` |
| `scroll_snap_y` | | Where to align the snappable children vertically |
| `scroll_dir` | | The allowed scroll direction(s), see `lv_dir_t` |
| `layer_type` | | Cache the layer type here. Element of lv\_intermediate\_layer\_type\_t |
| `name_static` | | 1: `name` was not dynamically allocated |
\_lv_obj_t [#_lv_obj_t]
| Member | Type | Description |
| ------------------------------ | -------------------------------------------------------------------- | --------------------------------------------------------------------------------------------------- |
| `ext_data` | | |
| `class_p` | | |
| `parent` | | |
| `spec_attr` | | |
| `styles` | | |
| `user_data` | `void *` | |
| `id` | `void *` | |
| `coords` | | |
| `flags` | | |
| `state` | | |
| `layout_inv` | | |
| `readjust_scroll_after_layout` | | |
| `scr_layout_inv` | | |
| `skip_trans` | | |
| `style_cnt` | | |
| `h_layout` | | |
| `w_layout` | | |
| `h_ignore_size` | | |
| `w_ignore_size` | | |
| `is_deleting` | | |
| `radio_button` | | Allow only one RADIO\_BUTTON sibling to be checked |
| `rendered` | | The widget is rendered at least once already. It's used to skip initial animations and transitions. |
* `lv_screen_load` — param `scr`
Typedefs [#typedefs]
lv_obj_spec_attr_t [#lv_obj_spec_attr_t]
```c title=" " lineNumbers=1
typedef struct _lv_obj_spec_attr_t lv_obj_spec_attr_t
```
Special, rarely used attributes. They are allocated automatically if any elements is set.
Dependencies [#dependencies]