@Override public void insertString(FilterBypass fb,
                                               int          offset,
                                               String       string,
                                               AttributeSet attr) {
                // we never use it, we never invoke Document.insertString
                // note that normal (non programmatically) editing only invokes
                // replace/remove
            }
@Override public void insertString(FilterBypass fb,
                                               int          offset,
                                               String       string,
                                               AttributeSet attr)