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


NAME
       XSetErrorHandler, XGetErrorText, XDisplayName, XSetIOEr
       rorHandler, 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



X Version 11		   Release 6.1				1





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


       BadName errors from OpenFont, LookupColor, or AllocNamed_
       Color protocol requests or on BadFont errors from a Query_
       Font 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 cur
       rent 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 connec
       tion 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 pre
       defined ``application names'' to report errors.	In these
       names, uppercase and lowercase matter.




X Version 11		   Release 6.1				2





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


       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 argu
		 ment.	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 argu
		 ment.

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




































X Version 11		   Release 6.1				3


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