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feat(obj): add lv_obj_null_on_delete (#6599)

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Liam 2024-08-13 11:58:03 -04:00 committed by GitHub
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23
docs/overview/obj.rst
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@ -167,6 +167,29 @@ using :cpp:expr:`lv_obj_clean(obj)`.
You can use :cpp:expr:`lv_obj_delete_delayed(obj, 1000)` to delete an object after
some time. The delay is expressed in milliseconds.
Sometimes you're not sure whether an object was deleted and you need some way to
check if it's still "alive". Anytime before the object is deleted, you can use
cpp:expr:`lv_obj_null_on_delete(&obj)` to cause your object pointer to be set to ``NULL``
when the object is deleted.
Make sure the pointer variable itself stays valid until the object is deleted. Here
is an example:
.. code:: c
void some_timer_callback(lv_timer_t * t)
{
static lv_obj_t * my_label;
if(my_label == NULL) {
my_label = lv_label_create(lv_screen_active());
lv_obj_delete_delayed(my_label, 1000);
lv_obj_null_on_delete(&my_label);
}
else {
lv_obj_set_x(my_label, lv_obj_get_x(my_label) + 1);
}
}
.. _objects_screens:
Screens

12
src/core/lv_obj.c
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@ -50,6 +50,7 @@ static void draw_scrollbar(lv_obj_t * obj, lv_layer_t * layer);
static lv_result_t scrollbar_init_draw_dsc(lv_obj_t * obj, lv_draw_rect_dsc_t * dsc);
static bool obj_valid_child(const lv_obj_t * parent, const lv_obj_t * obj_to_find);
static void update_obj_state(lv_obj_t * obj, lv_state_t new_state);
static void null_on_delete_cb(lv_event_t * e);
#if LV_USE_OBJ_PROPERTY
static lv_result_t lv_obj_set_any(lv_obj_t *, lv_prop_id_t, const lv_property_t *);
@ -426,6 +427,11 @@ bool lv_obj_is_valid(const lv_obj_t * obj)
return false;
}
void lv_obj_null_on_delete(lv_obj_t ** obj_ptr)
{
lv_obj_add_event_cb(*obj_ptr, null_on_delete_cb, LV_EVENT_DELETE, obj_ptr);
}
#if LV_USE_OBJ_ID
void lv_obj_set_id(lv_obj_t * obj, void * id)
{
@ -988,6 +994,12 @@ static bool obj_valid_child(const lv_obj_t * parent, const lv_obj_t * obj_to_fin
return false;
}
static void null_on_delete_cb(lv_event_t * e)
{
lv_obj_t ** obj_ptr = lv_event_get_user_data(e);
*obj_ptr = NULL;
}
#if LV_USE_OBJ_PROPERTY
static lv_result_t lv_obj_set_any(lv_obj_t * obj, lv_prop_id_t id, const lv_property_t * prop)
{

8
src/core/lv_obj.h
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@ -375,6 +375,14 @@ const lv_obj_class_t * lv_obj_get_class(const lv_obj_t * obj);
*/
bool lv_obj_is_valid(const lv_obj_t * obj);
/**
* Utility to set an object reference to NULL when it gets deleted.
* The reference should be in a location that will not become invalid
* during the object's lifetime, i.e. static or allocated.
* @param obj_ptr a pointer to a pointer to an object
*/
void lv_obj_null_on_delete(lv_obj_t ** obj_ptr);
#if LV_USE_OBJ_ID
/**
* Set an id for an object.