XSetErrorHandler(3X11)	       XLIB FUNCTIONS	       XSetErrorHandler(3X11)



NAME
  XSetErrorHandler, XGetErrorText, XDisplayName, XSetIOErrorHandler, XGetEr-
  rorDatabaseText - 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 descrip-
	    tion.

  default_string
	    Specifies the default error message if none is found in the data-
	    base.

  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, Lookup-
  Color, 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 XOpen-
  Display would attempt to use.	 This makes it easier to report to the user
  precisely which display the program attempted to open when the initial con-
  nection 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 func-
  tion 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 encod-
  ing 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 ``applica-
  tion 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