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_return,
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 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 XOpenDis-
play 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 re-
turn. 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 de-
fault_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 en-
coding 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 “ap-
plication names” to report errors. In these names, uppercase and lower-
case 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 argu-
ment.
SEE ALSO
XOpenDisplay(3), XSynchronize(3)
Xlib - C Language X Interface
X Version 11 libX11 1.8.12 XSetErrorHandler(3)
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