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



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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.
       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 default_string is assumed
       to be in the encoding of the current locale.  The
       buffer_return text 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 (uppercase and low-
       ercase matter):

       XProtoError
                 The protocol error number is used as a string



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


                 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






































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