XtSetLanguageProc - set the language procedure
#include <X11/Intrinsic.h>
XtLanguageProc XtSetLanguageProc(XtAppContext
    app_context, XtLanguageProc proc, XtPointer
    client_data);
  - app_context
- Specifies the application context in which the language procedure is to be
      used, or NULL.
- proc
- Specifies the language procedure, or NULL.
- client_data
- Specifies additional client data to be passed to the language procedure
      when it is called.
XtSetLanguageProc sets the language procedure that will be called from
  XtDisplayInitialize for all subsequent Displays initialized in the
  specified application context. If app_context is NULL, the specified
  language procedure is registered in all application contexts created by the
  calling process, including any future application contexts that may be
  created. If proc is NULL a default language procedure is registered.
  XtSetLanguageProc returns the previously registered language procedure.
  If a language procedure has not yet been registered, the return value is
  unspecified but if this return value is used in a subsequent call to
  XtSetLanguageProc, it will cause the default language procedure to be
  registered.The default language procedure does the following:
  - Sets the locale according to the environment. On ANSI C-based systems this
      is done by calling setlocale( LC_ALL, language ). If an
      error is encountered a warning message is issued with
    XtWarning.
- Calls XSupportsLocale to verify that the current locale is
      supported. If the locale is not supported, a warning message is issued
      with XtWarning and the locale is set to “C”.
- Calls XSetLocaleModifiers specifying the empty string.
- Returns the value of the current locale. On ANSI C-based systems this is
      the return value from a final call to setlocale( LC_ALL,
      NULL ).
A client wishing to use this mechanism to establish locale can do
    so by calling XtSetLanguageProc prior to
  XtDisplayInitialize.
X Toolkit Intrinsics - C Language Interface
Xlib - C Language X Interface