code: public FormattedStringBuilder fill(int newLength, char c) {
          int lineStart = _delegate.lastIndexOf(NL);
          if (lineStart == -1) {
              return fillBuffer(newLength, c);
          }
          lineStart += NL.length();
          return fillBuffer(lineStart + newLength, c);
      }
docs: Attempts to append <tt>c</tt> until the current line gets the length <tt>
  newLength</tt>. If the line is already as long or longer than <tt>
  newLength</tt>, then nothing is appended.
  @param newLength Minimal new length of the last line.
  @param c Character to append.
  @return The updated instance of FormattedStringBuilder.