XSetErrorHandler(3X11)               SysV               XSetErrorHandler(3X11)



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

SYNTAX
     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;

     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.  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 XGetErrorText function copies a null-terminated string describing the
     specified error code into the specified buffer.  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.

     The XGetErrorDatabaseText function returns a message (or the default
     message) from the error message database.  Xlib uses this function
     internally to look up its error messages.  On a UNIX-based system, the
     error message database is /usr/lib/X11/XErrorDB.

     The name argument should generally be the name of your application.  The
     message argument should indicate which type of error message you want.
     Xlib uses three predefined message types 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.

     XRequest  The major 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
     XSynchronize(3X11)
     Xlib - C Language X Interface