a string, naming the user data pointer
function to dup the value
passed as user_data to @dup_func
the result of calling @dup_func on the value associated with @key on @object, or %NULL if not set. If @dup_func is %NULL, the value is returned unmodified.
2.34
This is a variant of g_object_get_data() which returns a 'duplicate' of the value. @dup_func defines the meaning of 'duplicate' in this context, it could e.g. take a reference on a ref-counted object.
If the @key is not set on the object then @dup_func will be called with a %NULL argument.
Note that @dup_func is called while user data of @object is locked.
This function can be useful to avoid races when multiple threads are using object data on the same key on the same object.