XtGetActionKeysym man page
XtGetActionKeysym — obtain corresponding keysym
KeySym XtGetActionKeysym(XEvent* event, Modifiers* modifiers_return);
Specifies the event pointer passed to the action procedure by the Intrinsics.
Returns the modifiers that caused the match, if non-NULL.
If XtGetActionKeysym is called after an action procedure has been invoked by the Intrinsics and before that action procedure returns, and if the event pointer has the same value as the event pointer passed to that action routine, and if the event is a KeyPress or KeyRelease event, then XtGetActionKeysym returns the KeySym that matched the final event specification in the translation table and, if modifiers_return is non-NULL, the modifier state actually used to generate this KeySym; otherwise, if the event is a KeyPress or KeyRelease event, then XtGetActionKeysym calls XtTranslateKeycode and returns the results; else it returns NoSymbol and does not examine modifiers_return.
X Toolkit Intrinsics - C Language Interface
Xlib - C Language X Interface