By default, the external client widget has navigation type ‘XmTAB_GROUP’.
The widget traversal keystrokes are modified slightly from the standard XmPrimitive keystrokes. In particular, <TAB> alone does not traverse to the next widget (Ctrl-<TAB> must be used instead), but functions like a normal <TAB> in Emacs. This follows the semantics of the Motif text widget. The traversal keystrokes Ctrl-<TAB> and Shift-<TAB> are silently filtered by the external client widget and are not seen by Emacs.