XSetErrorHandler(3X1X)Version 11 (Release 6XSetErrorHandler(3X11)
NAME
XSetErrorHandler, XGetErrorText, XDisplayName,
XSetIOErrorHandler, 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.
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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 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 predefined
``application names'' to report errors. In these names,
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XSetErrorHandler(3X1X)Version 11 (Release 6XSetErrorHandler(3X11)
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(3X11), XSynchronize(3X11)
Xlib - C Language X Interface
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