+/**
+ * Function to register a hook function for a viewer to show
+ *the content of the viewer.
+ * It will be called by the constructor of the viewer.
+ * @param hook hook function of the viewer.
+ * @param hook_data hook data associated with the hook function.
+ * @param main_win the main window the viewer belongs to.
+ */
+
+void reg_show_viewer(LttvHook hook, gpointer hook_data,
+ MainWindow *main_win);
+
+
+/**
+ * Function to unregister a viewer's hook function which is used to
+ * show the content of the viewer..
+ * It will be called by the destructor of the viewer.
+ * @param hook hook function of the viewer.
+ * @param hook_data hook data associated with the hook function.
+ * @param main_win the main window the viewer belongs to.
+ */
+
+void unreg_show_viewer(LttvHook hook, gpointer hook_data,
+ MainWindow * main_win);
+
+
+/**
+ * Function to show each viewer in the current tab.
+ * It will be called by main window after it called process_traceset
+ * @param main_win the main window the viewer belongs to.
+ */
+
+void show_viewer(MainWindow *main_win);
+
+