+/**
+ * Function to register a hook function for a viewer to set/update its
+ * current position.
+ *
+ * @param tab the tab the viewer belongs to.
+ * @param hook hook function of the viewer that updates the current time. The
+ * call_data is a LttTime* representing the new current time.
+ * @param hook_data hook data associated with the hook function. It will
+ * be typically a pointer to the viewer's data structure.
+ */
+
+void lttvwindow_register_current_position_notify(Tab *tab,
+ LttvHook hook,
+ gpointer hook_data);
+
+
+/**
+ * Function to unregister a viewer's hook function which is used to
+ * set/update the current position of the viewer.
+ * @param tab the tab the viewer belongs to.
+ * @param hook hook function of the viewer that updates the current time. The
+ * call_data is a LttTime* representing the new current time.
+ * @param hook_data hook data associated with the hook function. It will
+ * be typically a pointer to the viewer's data structure.
+ */
+
+void lttvwindow_unregister_current_position_notify(Tab *tab,
+ LttvHook hook,
+ gpointer hook_data);
+
+