This function should be called whenever keyboard navigation within a single widget hits a boundary. The function emits thesignal on the widget and its return value should be interpreted in a way similar to the return value of gtk_widget_child_focus(): When %TRUE is returned, stay in the widget, the failed keyboard navigation is Ok and/or there is nowhere we can/should move the focus to. When %FALSE is returned, the caller should continue with keyboard navigation outside the widget, e.g. by calling gtk_widget_child_focus() on the widget's toplevel. The default ::keynav-failed handler returns %TRUE for %GTK_DIR_TAB_FORWARD and %GTK_DIR_TAB_BACKWARD. For the other values of , it looks at the setting and returns %FALSE if the setting is %TRUE. This way the entire user interface becomes cursor-navigatable on input devices such as mobile phones which only have cursor keys but no tab key. Whenever the default handler returns %TRUE, it also calls gtk_widget_error_bell() to notify the user of the failed keyboard navigation. A use case for providing an own implementation of ::keynav-failed (either by connecting to it or by overriding it) would be a row of widgets where the user should be able to navigate the entire row with the cursor keys, as e.g. known from user interfaces that require entering license keys. if the emitting widget should try to handle the keyboard navigation attempt in its parent container(s).