docs: Explain that NULL is not a valid value for name/description

diff --git a/atk/atkobject.c b/atk/atkobject.c
index 23e4605..251ae6b 100755 (executable)
--- a/atk/atkobject.c
+++ b/atk/atkobject.c
@@ -996,7 +996,10 @@ atk_object_get_index_in_parent (AtkObject *accessible)
  * @accessible: an #AtkObject
  * @name: a character string to be set as the accessible name
  *
- * Sets the accessible name of the accessible.
+ * Sets the accessible name of the accessible. You can't set the name
+ * to NULL. This is reserved for the initial value. In this aspect
+ * NULL is similar to ATK_ROLE_UNKNOWN. If you want to set the name to
+ * a empty value you can use "".
  **/
 void
 atk_object_set_name (AtkObject    *accessible,
@@ -1025,7 +1028,10 @@ atk_object_set_name (AtkObject    *accessible,
  * @accessible: an #AtkObject
  * @description: a character string to be set as the accessible description
  *
- * Sets the accessible description of the accessible.
+ * Sets the accessible description of the accessible. You can't set
+ * the description to NULL. This is reserved for the initial value. In
+ * this aspect NULL is similar to ATK_ROLE_UNKNOWN. If you want to set
+ * the name to a empty value you can use "".
  **/
 void
 atk_object_set_description (AtkObject   *accessible,