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.

     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; the returned value is
          ignored.  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 text in the default_string argument is
          assumed to be in the encoding of the current locale, and the
          text stored in the buffer_return argument 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.  In these names,
          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.

          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