char *(*XESetErrorString(display, extension, proc))()
Display *display;
int extension;
char *(*proc)();
| display | Specifies the connection to the X server. |
| extension | Specifies the extension number. |
| proc | Specifies the procedure to call to obtain an error string. |
(*proc)(display, code, codes, buffer, nbytes)
Display *display;
int code;
XExtCodes *codes;
char *buffer;
int nbytes;
Your procedure is called with the error code for every error detected. You should copy nbytes of a null-terminated string containing the error message into buffer.