XSetErrorHandler(3X11)XSetErrorHandler(3X11)NAME
XSetErrorHandler, XGetErrorText, XDisplayName, XSetIOErrorHandler,
XGetErrorDatabaseText - default error handlers
SYNOPSIS
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, buf‐
fer_return, length)
Display *display;
char *name, *message;
char *default_string;
char *buffer_return;
int length;
ARGUMENTS
Returns the error description. Specifies the error code for which you
want to obtain a description. Specifies the default error message if
none is found in the database. Specifies the connection to the X
server. Specifies the program's supplied error handler. Specifies the
size of the buffer. Specifies the type of the error message. Speci‐
fies the name of the application. 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 con‐
dition is not assumed to be fatal, it is acceptable for your error han‐
dler to return; the returned value is ignored. However, the error han‐
dler should not call any functions (directly or indirectly) on the dis‐
play 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, XDis‐
playName looks in the environment for the display and returns the dis‐
play 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 pre‐
defined “application names” to report errors. In these names, uppercase
and lowercase matter. The protocol error number is used as a string
for the message argument. These are the message strings that are used
internally by the library. For a core protocol request, the major
request protocol number is used for the message argument. For an exten‐
sion 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 ALSOXOpenDisplay(3X11), XSynchronize(3X11)
Xlib -- C Language X Interface
XSetErrorHandler(3X11)
