Sets the current cursor position to point to an <link linkend="cursor-alphabet">Alphabetic Index</link>.
See: set_alphabetic_index_sync.
This asynchronous call is completed with a call to set_alphabetic_index.end from the specified callback
.
| this | |
| index |
the alphabetic index |
| cancellable |
a Cancellable to optionally cancel this operation while in progress |
| callback |
callback to call when a result is ready |
| user_data |
user data for the |