const FlutterLogoDecoration({Map<int, Color> swatch: _kDefaultSwatch, Color textColor: const Color(0xFF616161), FlutterLogoStyle style: FlutterLogoStyle.markOnly, EdgeInsets margin: EdgeInsets.zero })

Creates a decoration that knows how to paint Flutter's logo.

The swatch controls the color used for the logo. The style controls whether and where to draw the "Flutter" label. If one is shown, the textColor controls the color of the label.

The swatch, textColor, and style arguments must not be null.

Source 

const FlutterLogoDecoration({
  this.swatch: _kDefaultSwatch,
  this.textColor: const Color(0xFF616161),
  FlutterLogoStyle style: FlutterLogoStyle.markOnly,
  this.margin: EdgeInsets.zero,
}) : style = style,
     _position = style == FlutterLogoStyle.markOnly ? 0.0 : style == FlutterLogoStyle.horizontal ? 1.0 : -1.0, // ignore: CONST_EVAL_TYPE_BOOL_NUM_STRING
     // (see https://github.com/dart-lang/sdk/issues/26980 for details about that ignore statement)
     _opacity = 1.0;