XSetErrorHandler(3) XLIB FUNCTIONS XSetErrorHandler(3)
NAME
XSetErrorHandler, XGetErrorText, XDisplayName, XSetIOErrorHandler, XSe-
tIOErrorExitHandler, 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_re-
turn, int length);
ARGUMENTS
buffer_return
Returns the error description.
code Specifies the error code for which you want to obtain a de-
scription.
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 re-
flected 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 at-
tempted 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 XSetIOErrorEx-
itHandler 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 pre-
defined “application names” to report errors. In these names, upper-
case 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 num-
ber is used for the message argument. For an extension re-
quest, the extension name (as given by InitExtension) fol-
lowed 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
X Version 11 libX11 1.8.4 XSetErrorHandler(3)
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