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,
Returns the error description.
Specifies the error code for which you want to obtain a description.
Specifies the default error message if none is found in the database.
Specifies the connection to the X server.
Specifies the program's supplied error handler.
Specifies the size of the buffer.
Specifies the type of the error message.
Specifies the name of the application.
Specifies the character string.
Xlib generally calls the program's
supplied error handler whenever an error is received.
It is not called on
protocol requests or on
errors from a
These errors generally are reflected back to the program through the
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.
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.
function returns the name of the display that
would attempt to use.
If a NULL string is specified,
looks in the environment for the display and returns the display name that
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.
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.
function returns a null-terminated message
(or the default message) from the error message
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.
The protocol error number is used as a string for the message argument.
These are the message strings that are used internally by the library.
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
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.