Gets the number of values that were added to the set.
For example, if the set is empty, 0 is returned.
Note that this function returns a `guint64`, because when all values are set, the return value is `G_MAXUINT + 1`. Unless you are sure this cannot happen (it can't with `GListModel`), be sure to use a 64bit type.
this |
a `GtkBitset` |
The number of values in the set. |