XSetErrorHandler(3X11)
X Version 11 (Release 4
X)
SetErrorHandler(3X11)



  NAME
       XSetErrorHandler, XGetErrorText, XDisplayName,
       XSetIOErrorHandler, 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.



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       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 previous
       error handler is returned.

       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.



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       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 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  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)


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       Xlib - C Language X Interface









































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