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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



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