anchor.diff:  
   class AnsiUp {
     AnsiUp()
  -      : bold = false,
  +      : style = StyledText.NONE,
           ansiColors = [
             [
               AnsiUpColor(rgb: [0, 0, 0], className: 'ansi-black'),
  
positive.code:   }
  
    late String _text;
    bool bold;
    List<List<AnsiUpColor>> ansiColors;
    List<AnsiUpColor> palette256;
    AnsiUpColor? fg;
  
negative.code:       fragment.text,
        fgColor: fragment.fg?.rgb?.toList(),
        bgColor: fragment.bg?.rgb?.toList(),
        textStyle: fragment.style,
      );
    }
  
    static const int NONE = 0;
    static const int BOLD = 1;
    static const int DIM = 2;
    static const int ITALIC = 4;
    static const int UNDERLINE = 8;
    static const int STRIKETHROUGH = 16;
    static const int BLINK = 32;
    static const int REVERSE = 64;
    static const int INVISIBLE = 128;
  
    final String text;
    final List<int>? fgColor;
    final List<int>? bgColor;
    final int textStyle;
    final String url;
  
    bool get bold => (textStyle & BOLD) == BOLD;
    bool get dim => (textStyle & DIM) == DIM;
    bool get italic => (textStyle & ITALIC) == ITALIC;
    bool get underline => (textStyle & UNDERLINE) == UNDERLINE;
    bool get strikethrough => (textStyle & STRIKETHROUGH) == STRIKETHROUGH;
    bool get blink => (textStyle & BLINK) == BLINK;
    bool get reverse => (textStyle & REVERSE) == REVERSE;
    bool get invisible => (textStyle & INVISIBLE) == INVISIBLE;
  
    String get style {
      if (fgColor == null && bgColor == null && textStyle == NONE) {
        return '';
      }
  
      String? decoration;
      if (underline) {
        decoration = (decoration == null) ? 'underline' : '$decoration underline';
      }
      if (strikethrough) {
        decoration =
            (decoration == null) ? 'line-through' : '$decoration line-through';
      }
  
      final _bgColor = bgColor;
      final _fgColor = fgColor;
      return <String>[
        if (_bgColor != null) 'background-color: ${_colorToCss(_bgColor)}',
        if (_fgColor != null) 'color: ${_colorToCss(_fgColor)}',
        if (bold) 'font-weight: bold',
        if (italic) 'font-style: italic',
        if (decoration != null) 'text-decoration: $decoration',
      ].join(';');
    }
  }
  