packages/flutter/lib/src/painting/flutter_logo.dart - external/github.com/flutter/flutter.git - Git at Google

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.

 import 'dart:math' as math;
 import 'dart:typed_data';
 import 'dart:ui' as ui show Gradient, TextBox, lerpDouble;

 import 'package:flutter/services.dart';
 import 'package:flutter/foundation.dart';

 import 'basic_types.dart';
 import 'box_fit.dart';
 import 'decoration.dart';
 import 'fractional_offset.dart';
 import 'text_painter.dart';
 import 'text_span.dart';
 import 'text_style.dart';

 /// Possible ways to draw Flutter's logo.
 enum FlutterLogoStyle {
   /// Show only Flutter's logo, not the "Flutter" label.
   ///
   /// This is the default behavior for [FlutterLogoDecoration] objects.
   markOnly,

   /// Show Flutter's logo on the left, and the "Flutter" label to its right.
   horizontal,

   /// Show Flutter's logo above the "Flutter" label.
   stacked,
 }

 /// An immutable description of how to paint Flutter's logo.
 class FlutterLogoDecoration extends Decoration {
   /// Creates a decoration that knows how to paint Flutter's logo.
   ///
   /// The [lightColor] and [darkColor] are used to fill 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 [lightColor], [darkColor], [textColor], and [style] arguments must not
   /// be null.
   const FlutterLogoDecoration({
     this.lightColor: const Color(0xFF42A5F5), // Colors.blue[400]
     this.darkColor: const Color(0xFF0D47A1), // Colors.blue[900]
     this.textColor: const Color(0xFF616161),
     this.style: FlutterLogoStyle.markOnly,
     this.margin: EdgeInsets.zero,
   }) : _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;

   const FlutterLogoDecoration._(this.lightColor, this.darkColor, this.textColor, this.style, this._position, this._opacity, this.margin);

   /// The lighter of the two colors used to paint the logo.
   ///
   /// If possible, the default should be used. It corresponds to the 400 and 900
   /// values of [material.Colors.blue] from the Material library.
   ///
   /// If for some reason that color scheme is impractical, the same entries from
   /// [material.Colors.amber], [material.Colors.red], or
   /// [material.Colors.indigo] colors can be used. These are Flutter's secondary
   /// colors.
   ///
   /// In extreme cases where none of those four color schemes will work,
   /// [material.Colors.pink], [material.Colors.purple], or
   /// [material.Colors.cyan] can be used. These are Flutter's tertiary colors.
   final Color lightColor;

   /// The darker of the two colors used to paint the logo.
   ///
   /// See [lightColor] for more information about selecting the logo's colors.
   final Color darkColor;

   /// The color used to paint the "Flutter" text on the logo, if [style] is
   /// [FlutterLogoStyle.horizontal] or [FlutterLogoStyle.stacked]. The
   /// appropriate color is `const Color(0xFF616161)` (a medium gray), against a
   /// white background.
   final Color textColor;

   /// Whether and where to draw the "Flutter" text. By default, only the logo
   /// itself is drawn.
   // This property isn't actually used when painting. It's only really used to
   // set the internal _position property.
   final FlutterLogoStyle style;

   // The following are set when lerping, to represent states that can't be
   // represented by the constructor.
   final double _position; // -1.0 for stacked, 1.0 for horizontal, 0.0 for no logo
   final double _opacity; // 0.0 .. 1.0

   /// How far to inset the logo from the edge of the container.
   final EdgeInsets margin;

   bool get _inTransition => _opacity != 1.0 || (_position != -1.0 && _position != 0.0 && _position != 1.0);

   @override
   bool debugAssertIsValid() {
     assert(lightColor != null
         && darkColor != null
         && textColor != null
         && style != null
         && _position != null
         && _position.isFinite
         && _opacity != null
         && _opacity >= 0.0
         && _opacity <= 1.0
         && margin != null);
     return true;
   }

   @override
   bool get isComplex => !_inTransition;

   /// Linearly interpolate between two Flutter logo descriptions.
   ///
   /// Interpolates both the color and the style in a continuous fashion.
   ///
   /// See also [Decoration.lerp].
   static FlutterLogoDecoration lerp(FlutterLogoDecoration a, FlutterLogoDecoration b, double t) {
     assert(a == null || a.debugAssertIsValid());
     assert(b == null || b.debugAssertIsValid());
     if (a == null && b == null)
       return null;
     if (a == null) {
       return new FlutterLogoDecoration._(
         b.lightColor,
         b.darkColor,
         b.textColor,
         b.style,
         b._position,
         b._opacity * t.clamp(0.0, 1.0),
         b.margin * t,
       );
     }
     if (b == null) {
       return new FlutterLogoDecoration._(
         a.lightColor,
         a.darkColor,
         a.textColor,
         a.style,
         a._position,
         a._opacity * (1.0 - t).clamp(0.0, 1.0),
         a.margin * t,
       );
     }
     return new FlutterLogoDecoration._(
       Color.lerp(a.lightColor, b.lightColor, t),
       Color.lerp(a.darkColor, b.darkColor, t),
       Color.lerp(a.textColor, b.textColor, t),
       t < 0.5 ? a.style : b.style,
       a._position + (b._position - a._position) * t,
       (a._opacity + (b._opacity - a._opacity) * t).clamp(0.0, 1.0),
       EdgeInsets.lerp(a.margin, b.margin, t),
     );
   }

   @override
   FlutterLogoDecoration lerpFrom(Decoration a, double t) {
     assert(debugAssertIsValid());
     if (a is! FlutterLogoDecoration)
       return lerp(null, this, t);
     assert(a.debugAssertIsValid);
     return lerp(a, this, t);
   }

   @override
   FlutterLogoDecoration lerpTo(Decoration b, double t) {
     assert(debugAssertIsValid());
     if (b is! FlutterLogoDecoration)
       return lerp(this, null, t);
     assert(b.debugAssertIsValid());
     return lerp(this, b, t);
   }

   @override
   // TODO(ianh): better hit testing
   bool hitTest(Size size, Offset position) => true;

   @override
   BoxPainter createBoxPainter([VoidCallback onChanged]) {
     assert(debugAssertIsValid());
     return new _FlutterLogoPainter(this);
   }

   @override
   bool operator ==(dynamic other) {
     assert(debugAssertIsValid());
     if (identical(this, other))
       return true;
     if (other is! FlutterLogoDecoration)
       return false;
     final FlutterLogoDecoration typedOther = other;
     return lightColor == typedOther.lightColor
         && darkColor == typedOther.darkColor
         && textColor == typedOther.textColor
         && _position == typedOther._position
         && _opacity == typedOther._opacity;
   }

   @override
   int get hashCode {
     assert(debugAssertIsValid());
     return hashValues(
       lightColor,
       darkColor,
       textColor,
       _position,
       _opacity
     );
   }

   @override
   void debugFillProperties(DiagnosticPropertiesBuilder properties) {
     super.debugFillProperties(properties);
     properties.add(new DiagnosticsNode.message('$lightColor/$darkColor on $textColor'));
     properties.add(new EnumProperty<FlutterLogoStyle>('style', style));
     if (_inTransition)
       properties.add(new DiagnosticsNode.message('transition $_position:$_opacity'));
   }
 }


 /// An object that paints a [BoxDecoration] into a canvas.
 class _FlutterLogoPainter extends BoxPainter {
   _FlutterLogoPainter(this._config)
     : assert(_config != null),
       assert(_config.debugAssertIsValid()),
       super(null) {
     _prepareText();
   }

   final FlutterLogoDecoration _config;

   // these are configured assuming a font size of 100.0.
   TextPainter _textPainter;
   Rect _textBoundingRect;

   void _prepareText() {
     const String kLabel = 'Flutter';
     _textPainter = new TextPainter(
       text: new TextSpan(
         text: kLabel,
         style: new TextStyle(
           color: _config.textColor,
           fontFamily: 'Roboto',
           fontSize: 100.0 * 350.0 / 247.0, // 247 is the height of the F when the fontSize is 350, assuming device pixel ratio 1.0
           fontWeight: FontWeight.w300,
           textBaseline: TextBaseline.alphabetic,
         ),
       ),
       textDirection: TextDirection.ltr,
     );
     _textPainter.layout();
     final ui.TextBox textSize = _textPainter.getBoxesForSelection(const TextSelection(baseOffset: 0, extentOffset: kLabel.length)).single;
     _textBoundingRect = new Rect.fromLTRB(textSize.left, textSize.top, textSize.right, textSize.bottom);
   }

   // This class contains a lot of magic numbers. They were derived from the
   // values in the SVG files exported from the original artwork source.

   void _paintLogo(Canvas canvas, Rect rect) {
     // Our points are in a coordinate space that's 166 pixels wide and 202 pixels high.
     // First, transform the rectangle so that our coordinate space is a square 202 pixels
     // to a side, with the top left at the origin.
     canvas.save();
     canvas.translate(rect.left, rect.top);
     canvas.scale(rect.width / 202.0, rect.height / 202.0);
     // Next, offset it some more so that the 166 horizontal pixels are centered
     // in that square (as opposed to being on the left side of it). This means
     // that if we draw in the rectangle from 0,0 to 166,202, we are drawing in
     // the center of the given rect.
     canvas.translate((202.0 - 166.0) / 2.0, 0.0);

     // Set up the styles.
     final Paint lightPaint = new Paint()
       ..color = _config.lightColor.withOpacity(0.8);
     final Paint mediumPaint = new Paint()
       ..color = _config.lightColor;
     final Paint darkPaint = new Paint()
       ..color = _config.darkColor;

     final ui.Gradient triangleGradient = new ui.Gradient.linear(
       const Offset(87.2623 + 37.9092, 28.8384 + 123.4389),
       const Offset(42.9205 + 37.9092, 35.0952 + 123.4389),
       <Color>[
         const Color(0xBFFFFFFF),
         const Color(0xBFFCFCFC),
         const Color(0xBFF4F4F4),
         const Color(0xBFE5E5E5),
         const Color(0xBFD1D1D1),
         const Color(0xBFB6B6B6),
         const Color(0xBF959595),
         const Color(0xBF6E6E6E),
         const Color(0xBF616161),
       ],
       <double>[ 0.2690, 0.4093, 0.4972, 0.5708, 0.6364, 0.6968, 0.7533, 0.8058, 0.8219 ],
     );
     final Paint trianglePaint = new Paint()
       ..shader = triangleGradient
       ..blendMode = BlendMode.multiply;

     final ui.Gradient rectangleGradient = new ui.Gradient.linear(
       const Offset(62.3643 + 37.9092, 40.135 + 123.4389),
       const Offset(54.0376 + 37.9092, 31.8083 + 123.4389),
       <Color>[
         const Color(0x80FFFFFF),
         const Color(0x80FCFCFC),
         const Color(0x80F4F4F4),
         const Color(0x80E5E5E5),
         const Color(0x80D1D1D1),
         const Color(0x80B6B6B6),
         const Color(0x80959595),
         const Color(0x806E6E6E),
         const Color(0x80616161),
       ],
       <double>[ 0.4588, 0.5509, 0.6087, 0.6570, 0.7001, 0.7397, 0.7768, 0.8113, 0.8219 ],
     );
     final Paint rectanglePaint = new Paint()
       ..shader = rectangleGradient
       ..blendMode = BlendMode.multiply;

     // Draw the basic shape.
     final Path topBeam = new Path()
       ..moveTo(37.7, 128.9)
       ..lineTo(9.8, 101.0)
       ..lineTo(100.4, 10.4)
       ..lineTo(156.2, 10.4);
     canvas.drawPath(topBeam, lightPaint);

     final Path middleBeam = new Path()
       ..moveTo(156.2, 94.0)
       ..lineTo(100.4, 94.0)
       ..lineTo(79.5, 114.9)
       ..lineTo(107.4, 142.8);
     canvas.drawPath(middleBeam, lightPaint);

     final Path bottomBeam = new Path()
       ..moveTo(79.5, 170.7)
       ..lineTo(100.4, 191.6)
       ..lineTo(156.2, 191.6)
       ..lineTo(156.2, 191.6)
       ..lineTo(107.4, 142.8);
     canvas.drawPath(bottomBeam, darkPaint);

     canvas.save();
     canvas.transform(new Float64List.fromList(const <double>[
       // careful, this is in _column_-major order
       0.7071, -0.7071, 0.0, 0.0,
       0.7071, 0.7071, 0.0, 0.0,
       0.0, 0.0, 1.0, 0.0,
       -77.697, 98.057, 0.0, 1.0,
     ]));
     canvas.drawRect(new Rect.fromLTWH(59.8, 123.1, 39.4, 39.4), mediumPaint);
     canvas.restore();

     // The two gradients.
     final Path triangle = new Path()
       ..moveTo(79.5, 170.7)
       ..lineTo(120.9, 156.4)
       ..lineTo(107.4, 142.8);
     canvas.drawPath(triangle, trianglePaint);

     final Path rectangle = new Path()
       ..moveTo(107.4, 142.8)
       ..lineTo(79.5, 170.7)
       ..lineTo(86.1, 177.3)
       ..lineTo(114.0, 149.4);
     canvas.drawPath(rectangle, rectanglePaint);

     canvas.restore();
   }

   @override
   void paint(Canvas canvas, Offset offset, ImageConfiguration configuration) {
     offset += _config.margin.topLeft;
     final Size canvasSize = _config.margin.deflateSize(configuration.size);
     if (canvasSize.isEmpty)
       return;
     Size logoSize;
     if (_config._position > 0.0) {
       // horizontal style
       logoSize = const Size(820.0, 232.0);
     } else if (_config._position < 0.0) {
       // stacked style
       logoSize = const Size(252.0, 306.0);
     } else {
       // only the mark
       logoSize = const Size(202.0, 202.0);
     }
     final FittedSizes fittedSize = applyBoxFit(BoxFit.contain, logoSize, canvasSize);
     assert(fittedSize.source == logoSize);
     final Rect rect = FractionalOffset.center.inscribe(fittedSize.destination, offset & canvasSize);
     final double centerSquareHeight = canvasSize.shortestSide;
     final Rect centerSquare = new Rect.fromLTWH(
       offset.dx + (canvasSize.width - centerSquareHeight) / 2.0,
       offset.dy + (canvasSize.height - centerSquareHeight) / 2.0,
       centerSquareHeight,
       centerSquareHeight
     );

     Rect logoTargetSquare;
     if (_config._position > 0.0) {
       // horizontal style
       logoTargetSquare = new Rect.fromLTWH(rect.left, rect.top, rect.height, rect.height);
     } else if (_config._position < 0.0) {
       // stacked style
       final double logoHeight = rect.height * 191.0 / 306.0;
       logoTargetSquare = new Rect.fromLTWH(
         rect.left + (rect.width - logoHeight) / 2.0,
         rect.top,
         logoHeight,
         logoHeight
       );
     } else {
       // only the mark
       logoTargetSquare = centerSquare;
     }
     final Rect logoSquare = Rect.lerp(centerSquare, logoTargetSquare, _config._position.abs());

     if (_config._opacity < 1.0) {
       canvas.saveLayer(
         offset & canvasSize,
         new Paint()
           ..colorFilter = new ColorFilter.mode(
             const Color(0xFFFFFFFF).withOpacity(_config._opacity),
             BlendMode.modulate,
           )
       );
     }
     if (_config._position != 0.0) {
       if (_config._position > 0.0) {
         // horizontal style
         final double fontSize = 2.0 / 3.0 * logoSquare.height * (1 - (10.4 * 2.0) / 202.0);
         final double scale = fontSize / 100.0;
         final double finalLeftTextPosition = // position of text in rest position
           (256.4 / 820.0) * rect.width - // 256.4 is the distance from the left edge to the left of the F when the whole logo is 820.0 wide
           (32.0 / 350.0) * fontSize; // 32 is the distance from the text bounding box edge to the left edge of the F when the font size is 350
         final double initialLeftTextPosition = // position of text when just starting the animation
           rect.width / 2.0 - _textBoundingRect.width * scale;
         final Offset textOffset = new Offset(
           rect.left + ui.lerpDouble(initialLeftTextPosition, finalLeftTextPosition, _config._position),
           rect.top + (rect.height - _textBoundingRect.height * scale) / 2.0
         );
         canvas.save();
         if (_config._position < 1.0) {
           final Offset center = logoSquare.center;
           final Path path = new Path()
             ..moveTo(center.dx, center.dy)
             ..lineTo(center.dx + rect.width, center.dy - rect.width)
             ..lineTo(center.dx + rect.width, center.dy + rect.width)
             ..close();
           canvas.clipPath(path);
         }
         canvas.translate(textOffset.dx, textOffset.dy);
         canvas.scale(scale, scale);
         _textPainter.paint(canvas, Offset.zero);
         canvas.restore();
       } else if (_config._position < 0.0) {
         // stacked style
         final double fontSize = 0.35 * logoTargetSquare.height * (1 - (10.4 * 2.0) / 202.0);
         final double scale = fontSize / 100.0;
         if (_config._position > -1.0) {
           // This limits what the drawRect call below is going to blend with.
           canvas.saveLayer(_textBoundingRect, new Paint());
         } else {
           canvas.save();
         }
         canvas.translate(
           logoTargetSquare.center.dx - (_textBoundingRect.width * scale / 2.0),
           logoTargetSquare.bottom
         );
         canvas.scale(scale, scale);
         _textPainter.paint(canvas, Offset.zero);
         if (_config._position > -1.0) {
           canvas.drawRect(_textBoundingRect.inflate(_textBoundingRect.width * 0.5), new Paint()
             ..blendMode = BlendMode.modulate
             ..shader = new ui.Gradient.linear(
               new Offset(_textBoundingRect.width * -0.5, 0.0),
               new Offset(_textBoundingRect.width * 1.5, 0.0),
               <Color>[const Color(0xFFFFFFFF), const Color(0xFFFFFFFF), const Color(0x00FFFFFF), const Color(0x00FFFFFF)],
               <double>[ 0.0, math.max(0.0, _config._position.abs() - 0.1), math.min(_config._position.abs() + 0.1, 1.0), 1.0 ],
             )
           );
         }
         canvas.restore();
       }
     }
     _paintLogo(canvas, logoSquare);
     if (_config._opacity < 1.0)
       canvas.restore();
   }
 }
	// Copyright 2016 The Chromium Authors. All rights reserved.
	// Use of this source code is governed by a BSD-style license that can be
	// found in the LICENSE file.

	import 'dart:math' as math;
	import 'dart:typed_data';
	import 'dart:ui' as ui show Gradient, TextBox, lerpDouble;

	import 'package:flutter/services.dart';
	import 'package:flutter/foundation.dart';

	import 'basic_types.dart';
	import 'box_fit.dart';
	import 'decoration.dart';
	import 'fractional_offset.dart';
	import 'text_painter.dart';
	import 'text_span.dart';
	import 'text_style.dart';

	/// Possible ways to draw Flutter's logo.
	enum FlutterLogoStyle {
	/// Show only Flutter's logo, not the "Flutter" label.
	///
	/// This is the default behavior for [FlutterLogoDecoration] objects.
	markOnly,

	/// Show Flutter's logo on the left, and the "Flutter" label to its right.
	horizontal,

	/// Show Flutter's logo above the "Flutter" label.
	stacked,
	}

	/// An immutable description of how to paint Flutter's logo.
	class FlutterLogoDecoration extends Decoration {
	/// Creates a decoration that knows how to paint Flutter's logo.
	///
	/// The [lightColor] and [darkColor] are used to fill 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 [lightColor], [darkColor], [textColor], and [style] arguments must not
	/// be null.
	const FlutterLogoDecoration({
	this.lightColor: const Color(0xFF42A5F5), // Colors.blue[400]
	this.darkColor: const Color(0xFF0D47A1), // Colors.blue[900]
	this.textColor: const Color(0xFF616161),
	this.style: FlutterLogoStyle.markOnly,
	this.margin: EdgeInsets.zero,
	}) : _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;

	const FlutterLogoDecoration._(this.lightColor, this.darkColor, this.textColor, this.style, this._position, this._opacity, this.margin);

	/// The lighter of the two colors used to paint the logo.
	///
	/// If possible, the default should be used. It corresponds to the 400 and 900
	/// values of [material.Colors.blue] from the Material library.
	///
	/// If for some reason that color scheme is impractical, the same entries from
	/// [material.Colors.amber], [material.Colors.red], or
	/// [material.Colors.indigo] colors can be used. These are Flutter's secondary
	/// colors.
	///
	/// In extreme cases where none of those four color schemes will work,
	/// [material.Colors.pink], [material.Colors.purple], or
	/// [material.Colors.cyan] can be used. These are Flutter's tertiary colors.
	final Color lightColor;

	/// The darker of the two colors used to paint the logo.
	///
	/// See [lightColor] for more information about selecting the logo's colors.
	final Color darkColor;

	/// The color used to paint the "Flutter" text on the logo, if [style] is
	/// [FlutterLogoStyle.horizontal] or [FlutterLogoStyle.stacked]. The
	/// appropriate color is `const Color(0xFF616161)` (a medium gray), against a
	/// white background.
	final Color textColor;

	/// Whether and where to draw the "Flutter" text. By default, only the logo
	/// itself is drawn.
	// This property isn't actually used when painting. It's only really used to
	// set the internal _position property.
	final FlutterLogoStyle style;

	// The following are set when lerping, to represent states that can't be
	// represented by the constructor.
	final double _position; // -1.0 for stacked, 1.0 for horizontal, 0.0 for no logo
	final double _opacity; // 0.0 .. 1.0

	/// How far to inset the logo from the edge of the container.
	final EdgeInsets margin;

	bool get _inTransition => _opacity != 1.0 \|\| (_position != -1.0 && _position != 0.0 && _position != 1.0);

	@override
	bool debugAssertIsValid() {
	assert(lightColor != null
	&& darkColor != null
	&& textColor != null
	&& style != null
	&& _position != null
	&& _position.isFinite
	&& _opacity != null
	&& _opacity >= 0.0
	&& _opacity <= 1.0
	&& margin != null);
	return true;
	}

	@override
	bool get isComplex => !_inTransition;

	/// Linearly interpolate between two Flutter logo descriptions.
	///
	/// Interpolates both the color and the style in a continuous fashion.
	///
	/// See also [Decoration.lerp].
	static FlutterLogoDecoration lerp(FlutterLogoDecoration a, FlutterLogoDecoration b, double t) {
	assert(a == null \|\| a.debugAssertIsValid());
	assert(b == null \|\| b.debugAssertIsValid());
	if (a == null && b == null)
	return null;
	if (a == null) {
	return new FlutterLogoDecoration._(
	b.lightColor,
	b.darkColor,
	b.textColor,
	b.style,
	b._position,
	b._opacity * t.clamp(0.0, 1.0),
	b.margin * t,
	);
	}
	if (b == null) {
	return new FlutterLogoDecoration._(
	a.lightColor,
	a.darkColor,
	a.textColor,
	a.style,
	a._position,
	a._opacity * (1.0 - t).clamp(0.0, 1.0),
	a.margin * t,
	);
	}
	return new FlutterLogoDecoration._(
	Color.lerp(a.lightColor, b.lightColor, t),
	Color.lerp(a.darkColor, b.darkColor, t),
	Color.lerp(a.textColor, b.textColor, t),
	t < 0.5 ? a.style : b.style,
	a._position + (b._position - a._position) * t,
	(a._opacity + (b._opacity - a._opacity) * t).clamp(0.0, 1.0),
	EdgeInsets.lerp(a.margin, b.margin, t),
	);
	}

	@override
	FlutterLogoDecoration lerpFrom(Decoration a, double t) {
	assert(debugAssertIsValid());
	if (a is! FlutterLogoDecoration)
	return lerp(null, this, t);
	assert(a.debugAssertIsValid);
	return lerp(a, this, t);
	}

	@override
	FlutterLogoDecoration lerpTo(Decoration b, double t) {
	assert(debugAssertIsValid());
	if (b is! FlutterLogoDecoration)
	return lerp(this, null, t);
	assert(b.debugAssertIsValid());
	return lerp(this, b, t);
	}

	@override
	// TODO(ianh): better hit testing
	bool hitTest(Size size, Offset position) => true;

	@override
	BoxPainter createBoxPainter([VoidCallback onChanged]) {
	assert(debugAssertIsValid());
	return new _FlutterLogoPainter(this);
	}

	@override
	bool operator ==(dynamic other) {
	assert(debugAssertIsValid());
	if (identical(this, other))
	return true;
	if (other is! FlutterLogoDecoration)
	return false;
	final FlutterLogoDecoration typedOther = other;
	return lightColor == typedOther.lightColor
	&& darkColor == typedOther.darkColor
	&& textColor == typedOther.textColor
	&& _position == typedOther._position
	&& _opacity == typedOther._opacity;
	}

	@override
	int get hashCode {
	assert(debugAssertIsValid());
	return hashValues(
	lightColor,
	darkColor,
	textColor,
	_position,
	_opacity
	);
	}

	@override
	void debugFillProperties(DiagnosticPropertiesBuilder properties) {
	super.debugFillProperties(properties);
	properties.add(new DiagnosticsNode.message('$lightColor/$darkColor on $textColor'));
	properties.add(new EnumProperty<FlutterLogoStyle>('style', style));
	if (_inTransition)
	properties.add(new DiagnosticsNode.message('transition $_position:$_opacity'));
	}
	}


	/// An object that paints a [BoxDecoration] into a canvas.
	class _FlutterLogoPainter extends BoxPainter {
	_FlutterLogoPainter(this._config)
	: assert(_config != null),
	assert(_config.debugAssertIsValid()),
	super(null) {
	_prepareText();
	}

	final FlutterLogoDecoration _config;

	// these are configured assuming a font size of 100.0.
	TextPainter _textPainter;
	Rect _textBoundingRect;

	void _prepareText() {
	const String kLabel = 'Flutter';
	_textPainter = new TextPainter(
	text: new TextSpan(
	text: kLabel,
	style: new TextStyle(
	color: _config.textColor,
	fontFamily: 'Roboto',
	fontSize: 100.0 * 350.0 / 247.0, // 247 is the height of the F when the fontSize is 350, assuming device pixel ratio 1.0
	fontWeight: FontWeight.w300,
	textBaseline: TextBaseline.alphabetic,
	),
	),
	textDirection: TextDirection.ltr,
	);
	_textPainter.layout();
	final ui.TextBox textSize = _textPainter.getBoxesForSelection(const TextSelection(baseOffset: 0, extentOffset: kLabel.length)).single;
	_textBoundingRect = new Rect.fromLTRB(textSize.left, textSize.top, textSize.right, textSize.bottom);
	}

	// This class contains a lot of magic numbers. They were derived from the
	// values in the SVG files exported from the original artwork source.

	void _paintLogo(Canvas canvas, Rect rect) {
	// Our points are in a coordinate space that's 166 pixels wide and 202 pixels high.
	// First, transform the rectangle so that our coordinate space is a square 202 pixels
	// to a side, with the top left at the origin.
	canvas.save();
	canvas.translate(rect.left, rect.top);
	canvas.scale(rect.width / 202.0, rect.height / 202.0);
	// Next, offset it some more so that the 166 horizontal pixels are centered
	// in that square (as opposed to being on the left side of it). This means
	// that if we draw in the rectangle from 0,0 to 166,202, we are drawing in
	// the center of the given rect.
	canvas.translate((202.0 - 166.0) / 2.0, 0.0);

	// Set up the styles.
	final Paint lightPaint = new Paint()
	..color = _config.lightColor.withOpacity(0.8);
	final Paint mediumPaint = new Paint()
	..color = _config.lightColor;
	final Paint darkPaint = new Paint()
	..color = _config.darkColor;

	final ui.Gradient triangleGradient = new ui.Gradient.linear(
	const Offset(87.2623 + 37.9092, 28.8384 + 123.4389),
	const Offset(42.9205 + 37.9092, 35.0952 + 123.4389),
	<Color>[
	const Color(0xBFFFFFFF),
	const Color(0xBFFCFCFC),
	const Color(0xBFF4F4F4),
	const Color(0xBFE5E5E5),
	const Color(0xBFD1D1D1),
	const Color(0xBFB6B6B6),
	const Color(0xBF959595),
	const Color(0xBF6E6E6E),
	const Color(0xBF616161),
	],
	<double>[ 0.2690, 0.4093, 0.4972, 0.5708, 0.6364, 0.6968, 0.7533, 0.8058, 0.8219 ],
	);
	final Paint trianglePaint = new Paint()
	..shader = triangleGradient
	..blendMode = BlendMode.multiply;

	final ui.Gradient rectangleGradient = new ui.Gradient.linear(
	const Offset(62.3643 + 37.9092, 40.135 + 123.4389),
	const Offset(54.0376 + 37.9092, 31.8083 + 123.4389),
	<Color>[
	const Color(0x80FFFFFF),
	const Color(0x80FCFCFC),
	const Color(0x80F4F4F4),
	const Color(0x80E5E5E5),
	const Color(0x80D1D1D1),
	const Color(0x80B6B6B6),
	const Color(0x80959595),
	const Color(0x806E6E6E),
	const Color(0x80616161),
	],
	<double>[ 0.4588, 0.5509, 0.6087, 0.6570, 0.7001, 0.7397, 0.7768, 0.8113, 0.8219 ],
	);
	final Paint rectanglePaint = new Paint()
	..shader = rectangleGradient
	..blendMode = BlendMode.multiply;

	// Draw the basic shape.
	final Path topBeam = new Path()
	..moveTo(37.7, 128.9)
	..lineTo(9.8, 101.0)
	..lineTo(100.4, 10.4)
	..lineTo(156.2, 10.4);
	canvas.drawPath(topBeam, lightPaint);

	final Path middleBeam = new Path()
	..moveTo(156.2, 94.0)
	..lineTo(100.4, 94.0)
	..lineTo(79.5, 114.9)
	..lineTo(107.4, 142.8);
	canvas.drawPath(middleBeam, lightPaint);

	final Path bottomBeam = new Path()
	..moveTo(79.5, 170.7)
	..lineTo(100.4, 191.6)
	..lineTo(156.2, 191.6)
	..lineTo(156.2, 191.6)
	..lineTo(107.4, 142.8);
	canvas.drawPath(bottomBeam, darkPaint);

	canvas.save();
	canvas.transform(new Float64List.fromList(const <double>[
	// careful, this is in _column_-major order
	0.7071, -0.7071, 0.0, 0.0,
	0.7071, 0.7071, 0.0, 0.0,
	0.0, 0.0, 1.0, 0.0,
	-77.697, 98.057, 0.0, 1.0,
	]));
	canvas.drawRect(new Rect.fromLTWH(59.8, 123.1, 39.4, 39.4), mediumPaint);
	canvas.restore();

	// The two gradients.
	final Path triangle = new Path()
	..moveTo(79.5, 170.7)
	..lineTo(120.9, 156.4)
	..lineTo(107.4, 142.8);
	canvas.drawPath(triangle, trianglePaint);

	final Path rectangle = new Path()
	..moveTo(107.4, 142.8)
	..lineTo(79.5, 170.7)
	..lineTo(86.1, 177.3)
	..lineTo(114.0, 149.4);
	canvas.drawPath(rectangle, rectanglePaint);

	canvas.restore();
	}

	@override
	void paint(Canvas canvas, Offset offset, ImageConfiguration configuration) {
	offset += _config.margin.topLeft;
	final Size canvasSize = _config.margin.deflateSize(configuration.size);
	if (canvasSize.isEmpty)
	return;
	Size logoSize;
	if (_config._position > 0.0) {
	// horizontal style
	logoSize = const Size(820.0, 232.0);
	} else if (_config._position < 0.0) {
	// stacked style
	logoSize = const Size(252.0, 306.0);
	} else {
	// only the mark
	logoSize = const Size(202.0, 202.0);
	}
	final FittedSizes fittedSize = applyBoxFit(BoxFit.contain, logoSize, canvasSize);
	assert(fittedSize.source == logoSize);
	final Rect rect = FractionalOffset.center.inscribe(fittedSize.destination, offset & canvasSize);
	final double centerSquareHeight = canvasSize.shortestSide;
	final Rect centerSquare = new Rect.fromLTWH(
	offset.dx + (canvasSize.width - centerSquareHeight) / 2.0,
	offset.dy + (canvasSize.height - centerSquareHeight) / 2.0,
	centerSquareHeight,
	centerSquareHeight
	);

	Rect logoTargetSquare;
	if (_config._position > 0.0) {
	// horizontal style
	logoTargetSquare = new Rect.fromLTWH(rect.left, rect.top, rect.height, rect.height);
	} else if (_config._position < 0.0) {
	// stacked style
	final double logoHeight = rect.height * 191.0 / 306.0;
	logoTargetSquare = new Rect.fromLTWH(
	rect.left + (rect.width - logoHeight) / 2.0,
	rect.top,
	logoHeight,
	logoHeight
	);
	} else {
	// only the mark
	logoTargetSquare = centerSquare;
	}
	final Rect logoSquare = Rect.lerp(centerSquare, logoTargetSquare, _config._position.abs());

	if (_config._opacity < 1.0) {
	canvas.saveLayer(
	offset & canvasSize,
	new Paint()
	..colorFilter = new ColorFilter.mode(
	const Color(0xFFFFFFFF).withOpacity(_config._opacity),
	BlendMode.modulate,
	)
	);
	}
	if (_config._position != 0.0) {
	if (_config._position > 0.0) {
	// horizontal style
	final double fontSize = 2.0 / 3.0 * logoSquare.height * (1 - (10.4 * 2.0) / 202.0);
	final double scale = fontSize / 100.0;
	final double finalLeftTextPosition = // position of text in rest position
	(256.4 / 820.0) * rect.width - // 256.4 is the distance from the left edge to the left of the F when the whole logo is 820.0 wide
	(32.0 / 350.0) * fontSize; // 32 is the distance from the text bounding box edge to the left edge of the F when the font size is 350
	final double initialLeftTextPosition = // position of text when just starting the animation
	rect.width / 2.0 - _textBoundingRect.width * scale;
	final Offset textOffset = new Offset(
	rect.left + ui.lerpDouble(initialLeftTextPosition, finalLeftTextPosition, _config._position),
	rect.top + (rect.height - _textBoundingRect.height * scale) / 2.0
	);
	canvas.save();
	if (_config._position < 1.0) {
	final Offset center = logoSquare.center;
	final Path path = new Path()
	..moveTo(center.dx, center.dy)
	..lineTo(center.dx + rect.width, center.dy - rect.width)
	..lineTo(center.dx + rect.width, center.dy + rect.width)
	..close();
	canvas.clipPath(path);
	}
	canvas.translate(textOffset.dx, textOffset.dy);
	canvas.scale(scale, scale);
	_textPainter.paint(canvas, Offset.zero);
	canvas.restore();
	} else if (_config._position < 0.0) {
	// stacked style
	final double fontSize = 0.35 * logoTargetSquare.height * (1 - (10.4 * 2.0) / 202.0);
	final double scale = fontSize / 100.0;
	if (_config._position > -1.0) {
	// This limits what the drawRect call below is going to blend with.
	canvas.saveLayer(_textBoundingRect, new Paint());
	} else {
	canvas.save();
	}
	canvas.translate(
	logoTargetSquare.center.dx - (_textBoundingRect.width * scale / 2.0),
	logoTargetSquare.bottom
	);
	canvas.scale(scale, scale);
	_textPainter.paint(canvas, Offset.zero);
	if (_config._position > -1.0) {
	canvas.drawRect(_textBoundingRect.inflate(_textBoundingRect.width * 0.5), new Paint()
	..blendMode = BlendMode.modulate
	..shader = new ui.Gradient.linear(
	new Offset(_textBoundingRect.width * -0.5, 0.0),
	new Offset(_textBoundingRect.width * 1.5, 0.0),
	<Color>[const Color(0xFFFFFFFF), const Color(0xFFFFFFFF), const Color(0x00FFFFFF), const Color(0x00FFFFFF)],
	<double>[ 0.0, math.max(0.0, _config._position.abs() - 0.1), math.min(_config._position.abs() + 0.1, 1.0), 1.0 ],
	)
	);
	}
	canvas.restore();
	}
	}
	_paintLogo(canvas, logoSquare);
	if (_config._opacity < 1.0)
	canvas.restore();
	}
	}