The gpointer argument is passed to all three callbacks, not just one.
https://bugzilla.gnome.org/show_bug.cgi?id=731302
* or not.
* @fullcallback: the callback which will be called when the queue is considered full.
* @emptycallback: the callback which will be called when the queue is considered empty.
- * @checkdata: a #gpointer that will be given in the @checkfull callback.
+ * @checkdata: a #gpointer that will be passed to the @checkfull, @fullcallback,
+ * and @emptycallback callbacks.
*
* Creates a new #GstDataQueue. The difference with @gst_data_queue_new is that it will
* not emit the 'full' and 'empty' signals, but instead calling directly @fullcallback