XSetErrorHandler(3X11)      X Version 11(Release 5)      XSetErrorHandler(3X11)


NAME
      XSetErrorHandler, XGetErrorText, XDisplayName, XSetIOErrorHandler,
      XGetErrorDatabaseText - default error handlers

SYNTAX
      int (*XSetErrorHandler(handler))()
            int (*handler)(Display *, XErrorEvent *)

      XGetErrorText(display, code, buffer_return, length)
            Display *display;
            int code;
            char *buffer_return;
            int length;

      char *XDisplayName(string)
            char *string;

      int (*XSetIOErrorHandler(handler))()
            int (*handler)(Display *);

      XGetErrorDatabaseText(display, name, message, default_string,
      buffer_return, length)
            Display *display;
            char *name, *message;
            char *default_string;
            char *buffer_return;
            int length;

ARGUMENTS
      buffer_return
                Returns the error description.

      code      Specifies the error code for which you want to obtain a
                description.

      default_string
                Specifies the default error message if none is found in the
                database.

      display   Specifies the connection to the X server.

      handler   Specifies the program's supplied error handler.

      length    Specifies the size of the buffer.

      message   Specifies the type of the error message.

      name      Specifies the name of the application.

      string    Specifies the character string.




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XSetErrorHandler(3X11)      X Version 11(Release 5)      XSetErrorHandler(3X11)


DESCRIPTION
      Xlib generally calls the program's supplied error handler whenever an
      error is received.  It is not called on BadName errors from OpenFont,
      LookupColor, or AllocNamedColor protocol requests or on BadFont errors
      from a QueryFont protocol request.  These errors generally are reflected
      back to the program through the procedural interface.  Because this
      condition is not assumed to be fatal, it is acceptable for your error
      handler to return.  However, the error handler should not call any
      functions (directly or indirectly) on the display that will generate
      protocol requests or that will look for input events.  The previous error
      handler is returned.

      The XGetErrorText function copies a null-terminated string describing the
      specified error code into the specified buffer.  The returned text is in
      the encoding of the current locale.  It is recommended that you use this
      function to obtain an error description because extensions to Xlib may
      define their own error codes and error strings.

      The XDisplayName function returns the name of the display that
      XOpenDisplay would attempt to use.  If a NULL string is specified,
      XDisplayName looks in the environment for the display and returns the
      display name that XOpenDisplay would attempt to use.  This makes it
      easier to report to the user precisely which display the program
      attempted to open when the initial connection attempt failed.

      The XSetIOErrorHandler sets the fatal I/O error handler.  Xlib calls the
      program's supplied error handler if any sort of system call error occurs
      (for example, the connection to the server was lost).  This is assumed to
      be a fatal condition, and the called routine should not return.  If the
      I/O error handler does return, the client process exits.

      Note that the previous error handler is returned.

      The XGetErrorDatabaseText function returns a null-terminated message (or
      the default message) from the error message database.  Xlib uses this
      function internally to look up its error messages.  The default_string is
      assumed to be in the encoding of the current locale.  The buffer_return
      text is in the encoding of the current locale.

      The name argument should generally be the name of your application.  The
      message argument should indicate which type of error message you want.
      If the name and message are not in the Host Portable Character Encoding
      the result is implementation dependent.  Xlib uses three predefined
      ``application names'' to report errors (uppercase and lowercase matter):

      XProtoError
                The protocol error number is used as a string for the message
                argument.

      XlibMessage
                These are the message strings that are used internally by the
                library.


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      XRequest  For a core protocol request, the major request protocol number
                is used for the message argument.  For an extension request,
                the extension name (as given by InitExtension) followed by a
                period (.) and the minor request protocol number is used for
                the message argument.  If no string is found in the error
                database, the default_string is returned to the buffer
                argument.

SEE ALSO
      XOpenDisplay(3X11), XSynchronize(3X11)
      Xlib - C Language X Interface











































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