XtNameToWidget(), XtWindowToWidget() - translating strings to widgets or windows to widgets
Widget XtNameToWidget (Widget reference, String names)
Widget XtWindowToWidget (Display *display, Window window)
The XtNameToWidget(3) function looks for a widget whose name is the first component in the specified names and that is a pop-up child of reference (or a normal child if reference is a subclass of compositeWidgetClass). It then uses that widget as the new reference and repeats the search after deleting the first component from the specified names. If it cannot find the specified widget, XtNameToWidget(3) returns NULL.
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(3) 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(3) can return NULL if the single branch that it follows does not contain the named widget. That is, XtNameToWidget(3) does not back up and follow other matching branches of the widget tree.
The XtWindowToWidget(3) function translates the specified window and display pointer into the appropriate widget instance.
X Toolkit Intrinsics - C Language Interface
Xlib - C Language X Interface