NAME
XSetErrorHandler, XGetErrorText, XDisplayName, XSetIOErrorHandler,
XGetErrorDatabaseText - default error handlers
SYNTAX
int
(*XSetErrorHandler(int (* handler)(Display *, XErrorEvent *)))();
int
XGetErrorText(Display * display, int code, char *
buffer_return, int length);
char
*XDisplayName(char * string);
int
(*XSetIOErrorHandler(int (* handler)(Display *)))();
int
XGetErrorDatabaseText(Display * display, char *name, char *
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
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, 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(3), XSynchronize(3)
Xlib - C Language X Interface