Widget XtWindowToWidget(display, window)
Display *display;
Window window;
Note that the names argument contains the name of a widget with respect to the specified reference widget and can contain more than one widget name (separated by periods) for widgets that are not direct children of the specified reference widget.
If more than one child of the reference widget matches the name, XtNameToWidget can return any of the children. The Intrinsics do not require that all children of a widget have unique names. If the specified names contain more than one component and if more than one child matches the first component, XtNameToWidget can return NULL if the single branch that it follows does not contain the named widget. That is, XtNameToWidget does not back up and follow other matching branches of the widget tree.
The XtWindowToWidget function translates the specified window and display pointer into the appropriate widget instance.