XSetErrorHandler(3X11) XLIB FUNCTIONS XSetErrorHandler(3X11)NAME
XSetErrorHandler, XGetErrorText, XDisplayName, XSetIOEr-
rorHandler, XGetErrorDatabaseText - default error handlers
SYNTAX
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, buffer_return, length)
Display *display;
char *name, *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
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XSetErrorHandler(3X11) XLIB FUNCTIONS XSetErrorHandler(3X11)
BadName errors from OpenFont, LookupColor, or AllocNamed-
Color protocol requests or on BadFont errors from a Query-
Font 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 cur-
rent 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 connec-
tion 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-termi-
nated message (or the default message) from the error mes-
sage 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.
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XSetErrorHandler(3X11) XLIB FUNCTIONS XSetErrorHandler(3X11)
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 argu-
ment. 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 ALSOXOpenDisplay(3X11), XSynchronize(3X11)
Xlib - C Language X Interface
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