Sets the callback function storing the data as a refcounted callback
"object". This is used internally. Note that calling
g_source_set_callback_indirect() assumes
an initial reference count on callback_data, and thus
callback_funcs->unref will eventually be called once more
than callback_funcs->ref.
Sets the callback function storing the data as a refcounted callback "object". This is used internally. Note that calling g_source_set_callback_indirect() assumes an initial reference count on callback_data, and thus callback_funcs->unref will eventually be called once more than callback_funcs->ref.