anchor.diff:  
     GlobalKey get key => new GlobalObjectKey(this);
   
  -  Widget buildSwatch(BuildContext context, Widget child) {
  -    return new GestureDetector(
  -        onTap: () async {
  -          await SchedulerBinding.instance.endOfFrame;
  -          final Rect area = interestingArea;
  -          print('BASH: convert flutter_`printf %02d \$N`.png -crop '
  -              '${area.width}x${area.height}+${area.left}+${area.top} -resize '
  -              '\'400x600>\' ${filename}.png; ((N++))');
  -          Navigator.of(context).pop();
  -        },
  -        child: child);
  -  }
  -
     Rect get interestingArea {
       final RenderBox box = key.currentContext.findRenderObject();
  -    final Rect area =
  -        ((box.localToGlobal(Offset.zero) * ui.window.devicePixelRatio) &
  -            (box.size * ui.window.devicePixelRatio));
  +    final Rect area = ((box.localToGlobal(Offset.zero) * ui.window.devicePixelRatio) & (box.size * ui.window.devicePixelRatio));
       return area;
     }
   }
  
positive.code:   Widget build(BuildContext context) {
      List<Widget> items = <Widget>[];
      for (int key in keys) {
        Color textColor =
            ThemeData.estimateBrightnessForColor(swatch[key]) == Brightness.light
                ? Colors.black
                : Colors.white;
        TextStyle style = new TextStyle(color: textColor);
        String label;
        if (swatch[key].value == swatch.value) {
  
negative.code:     const SwatchPage('Colors.redAccent', Colors.redAccent, accentPalette),
      const SwatchPage('Colors.pinkAccent', Colors.pinkAccent, accentPalette),
      const SwatchPage('Colors.purpleAccent', Colors.purpleAccent, accentPalette),
      const SwatchPage('Colors.deepPurpleAccent', Colors.deepPurpleAccent, accentPalette),
      const SwatchPage('Colors.indigoAccent', Colors.indigoAccent, accentPalette),
      const SwatchPage('Colors.blueAccent', Colors.blueAccent, accentPalette),
      const SwatchPage('Colors.lightBlueAccent', Colors.lightBlueAccent, accentPalette),
      const SwatchPage('Colors.cyanAccent', Colors.cyanAccent, accentPalette),
      const SwatchPage('Colors.tealAccent', Colors.tealAccent, accentPalette),
      const SwatchPage('Colors.greenAccent', Colors.greenAccent, accentPalette),
      const SwatchPage('Colors.lightGreenAccent', Colors.lightGreenAccent, accentPalette),
      const SwatchPage('Colors.limeAccent', Colors.limeAccent, accentPalette),
      const SwatchPage('Colors.yellowAccent', Colors.yellowAccent, accentPalette),
      const SwatchPage('Colors.amberAccent', Colors.amberAccent, accentPalette),
      const SwatchPage('Colors.orangeAccent', Colors.orangeAccent, accentPalette),
      const SwatchPage('Colors.deepOrangeAccent', Colors.deepOrangeAccent, accentPalette),
      const SwatchPage('Colors.grey', Colors.grey, greyPalette),
      const ColorListPage('Colors.blacks', Colors.white, const <String, Color>{
        'black': Colors.black,
  