NAME

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

SYNTAX

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

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

       char *XDisplayName(_Xconst char *string);

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

       void (*XSetIOErrorExitHandler(Display *display, void (*handler)(Display *, void *), void *user_data))();

       int XGetErrorDatabaseText(Display *display, _Xconst char  *name,  _Xconst  char  *message,  _Xconst  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 normally not return.  If the I/O error
       handler does return, the client process  exits  by  default,  this  behavior  may  be  altered  with  the
       XSetIOErrorExitHandler function.

       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