NAME

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

SYNTAX

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

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

       char *XDisplayName(char *string);

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

       int XGetErrorDatabaseText(Display *display, char *name, char *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(3), XSynchronize(3)
       Xlib - C Language X Interface