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

 // Copyright 2014 The Flutter 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 'package:flutter/foundation.dart';

 import 'basic_types.dart';
 import 'border_radius.dart';
 import 'box_border.dart';
 import 'box_shadow.dart';
 import 'colors.dart';
 import 'decoration.dart';
 import 'decoration_image.dart';
 import 'edge_insets.dart';
 import 'gradient.dart';
 import 'image_provider.dart';

 /// An immutable description of how to paint a box.
 ///
 /// The [BoxDecoration] class provides a variety of ways to draw a box.
 ///
 /// The box has a [border], a body, and may cast a [boxShadow].
 ///
 /// The [shape] of the box can be a circle or a rectangle. If it is a rectangle,
 /// then the [borderRadius] property controls the roundness of the corners.
 ///
 /// The body of the box is painted in layers. The bottom-most layer is the
 /// [color], which fills the box. Above that is the [gradient], which also fills
 /// the box. Finally there is the [image], the precise alignment of which is
 /// controlled by the [DecorationImage] class.
 ///
 /// The [border] paints over the body; the [boxShadow], naturally, paints below it.
 ///
 /// {@tool snippet}
 ///
 /// The following applies a [BoxDecoration] to a [Container] widget to draw an
 /// [image] of an owl with a thick black [border] and rounded corners.
 ///
 /// ![](https://flutter.github.io/assets-for-api-docs/assets/painting/box_decoration.png)
 ///
 /// ```dart
 /// Container(
 ///   decoration: BoxDecoration(
 ///     color: const Color(0xff7c94b6),
 ///     image: const DecorationImage(
 ///       image: NetworkImage('https://flutter.github.io/assets-for-api-docs/assets/widgets/owl-2.jpg'),
 ///       fit: BoxFit.cover,
 ///     ),
 ///     border: Border.all(
 ///       color: Colors.black,
 ///       width: 8,
 ///     ),
 ///     borderRadius: BorderRadius.circular(12),
 ///   ),
 /// )
 /// ```
 /// {@end-tool}
 ///
 /// {@template flutter.painting.BoxDecoration.clip}
 /// The [shape] or the [borderRadius] won't clip the children of the
 /// decorated [Container]. If the clip is required, insert a clip widget
 /// (e.g., [ClipRect], [ClipRRect], [ClipPath]) as the child of the [Container].
 /// Be aware that clipping may be costly in terms of performance.
 /// {@endtemplate}
 ///
 /// See also:
 ///
 ///  * [DecoratedBox] and [Container], widgets that can be configured with
 ///    [BoxDecoration] objects.
 ///  * [CustomPaint], a widget that lets you draw arbitrary graphics.
 ///  * [Decoration], the base class which lets you define other decorations.
 class BoxDecoration extends Decoration {
   /// Creates a box decoration.
   ///
   /// * If [color] is null, this decoration does not paint a background color.
   /// * If [image] is null, this decoration does not paint a background image.
   /// * If [border] is null, this decoration does not paint a border.
   /// * If [borderRadius] is null, this decoration uses more efficient background
   ///   painting commands. The [borderRadius] argument must be null if [shape] is
   ///   [BoxShape.circle].
   /// * If [boxShadow] is null, this decoration does not paint a shadow.
   /// * If [gradient] is null, this decoration does not paint gradients.
   /// * If [backgroundBlendMode] is null, this decoration paints with [BlendMode.srcOver]
   ///
   /// The [shape] argument must not be null.
   const BoxDecoration({
     this.color,
     this.image,
     this.border,
     this.borderRadius,
     this.boxShadow,
     this.gradient,
     this.backgroundBlendMode,
     this.shape = BoxShape.rectangle,
   }) : assert(shape != null),
        assert(
          backgroundBlendMode == null || color != null || gradient != null,
          "backgroundBlendMode applies to BoxDecoration's background color or "
          'gradient, but no color or gradient was provided.',
        );

   /// Creates a copy of this object but with the given fields replaced with the
   /// new values.
   BoxDecoration copyWith({
     Color? color,
     DecorationImage? image,
     BoxBorder? border,
     BorderRadiusGeometry? borderRadius,
     List<BoxShadow>? boxShadow,
     Gradient? gradient,
     BlendMode? backgroundBlendMode,
     BoxShape? shape,
   }) {
     return BoxDecoration(
       color: color ?? this.color,
       image: image ?? this.image,
       border: border ?? this.border,
       borderRadius: borderRadius ?? this.borderRadius,
       boxShadow: boxShadow ?? this.boxShadow,
       gradient: gradient ?? this.gradient,
       backgroundBlendMode: backgroundBlendMode ?? this.backgroundBlendMode,
       shape: shape ?? this.shape,
     );
   }

   @override
   bool debugAssertIsValid() {
     assert(shape != BoxShape.circle || borderRadius == null); // Can't have a border radius if you're a circle.
     return super.debugAssertIsValid();
   }

   /// The color to fill in the background of the box.
   ///
   /// The color is filled into the [shape] of the box (e.g., either a rectangle,
   /// potentially with a [borderRadius], or a circle).
   ///
   /// This is ignored if [gradient] is non-null.
   ///
   /// The [color] is drawn under the [image].
   final Color? color;

   /// An image to paint above the background [color] or [gradient].
   ///
   /// If [shape] is [BoxShape.circle] then the image is clipped to the circle's
   /// boundary; if [borderRadius] is non-null then the image is clipped to the
   /// given radii.
   final DecorationImage? image;

   /// A border to draw above the background [color], [gradient], or [image].
   ///
   /// Follows the [shape] and [borderRadius].
   ///
   /// Use [Border] objects to describe borders that do not depend on the reading
   /// direction.
   ///
   /// Use [BoxBorder] objects to describe borders that should flip their left
   /// and right edges based on whether the text is being read left-to-right or
   /// right-to-left.
   final BoxBorder? border;

   /// If non-null, the corners of this box are rounded by this [BorderRadius].
   ///
   /// Applies only to boxes with rectangular shapes; ignored if [shape] is not
   /// [BoxShape.rectangle].
   ///
   /// {@macro flutter.painting.BoxDecoration.clip}
   final BorderRadiusGeometry? borderRadius;

   /// A list of shadows cast by this box behind the box.
   ///
   /// The shadow follows the [shape] of the box.
   ///
   /// See also:
   ///
   ///  * [kElevationToShadow], for some predefined shadows used in Material
   ///    Design.
   ///  * [PhysicalModel], a widget for showing shadows.
   final List<BoxShadow>? boxShadow;

   /// A gradient to use when filling the box.
   ///
   /// If this is specified, [color] has no effect.
   ///
   /// The [gradient] is drawn under the [image].
   final Gradient? gradient;

   /// The blend mode applied to the [color] or [gradient] background of the box.
   ///
   /// If no [backgroundBlendMode] is provided then the default painting blend
   /// mode is used.
   ///
   /// If no [color] or [gradient] is provided then the blend mode has no impact.
   final BlendMode? backgroundBlendMode;

   /// The shape to fill the background [color], [gradient], and [image] into and
   /// to cast as the [boxShadow].
   ///
   /// If this is [BoxShape.circle] then [borderRadius] is ignored.
   ///
   /// The [shape] cannot be interpolated; animating between two [BoxDecoration]s
   /// with different [shape]s will result in a discontinuity in the rendering.
   /// To interpolate between two shapes, consider using [ShapeDecoration] and
   /// different [ShapeBorder]s; in particular, [CircleBorder] instead of
   /// [BoxShape.circle] and [RoundedRectangleBorder] instead of
   /// [BoxShape.rectangle].
   ///
   /// {@macro flutter.painting.BoxDecoration.clip}
   final BoxShape shape;

   @override
   EdgeInsetsGeometry? get padding => border?.dimensions;

   @override
   Path getClipPath(Rect rect, TextDirection textDirection) {
     switch (shape) {
       case BoxShape.circle:
         final Offset center = rect.center;
         final double radius = rect.shortestSide / 2.0;
         final Rect square = Rect.fromCircle(center: center, radius: radius);
         return Path()..addOval(square);
       case BoxShape.rectangle:
         if (borderRadius != null)
           return Path()..addRRect(borderRadius!.resolve(textDirection).toRRect(rect));
         return Path()..addRect(rect);
     }
   }

   /// Returns a new box decoration that is scaled by the given factor.
   BoxDecoration scale(double factor) {
     return BoxDecoration(
       color: Color.lerp(null, color, factor),
       image: image, // TODO(ianh): fade the image from transparent
       border: BoxBorder.lerp(null, border, factor),
       borderRadius: BorderRadiusGeometry.lerp(null, borderRadius, factor),
       boxShadow: BoxShadow.lerpList(null, boxShadow, factor),
       gradient: gradient?.scale(factor),
       shape: shape,
     );
   }

   @override
   bool get isComplex => boxShadow != null;

   @override
   BoxDecoration? lerpFrom(Decoration? a, double t) {
     if (a == null)
       return scale(t);
     if (a is BoxDecoration)
       return BoxDecoration.lerp(a, this, t);
     return super.lerpFrom(a, t) as BoxDecoration?;
   }

   @override
   BoxDecoration? lerpTo(Decoration? b, double t) {
     if (b == null)
       return scale(1.0 - t);
     if (b is BoxDecoration)
       return BoxDecoration.lerp(this, b, t);
     return super.lerpTo(b, t) as BoxDecoration?;
   }

   /// Linearly interpolate between two box decorations.
   ///
   /// Interpolates each parameter of the box decoration separately.
   ///
   /// The [shape] is not interpolated. To interpolate the shape, consider using
   /// a [ShapeDecoration] with different border shapes.
   ///
   /// If both values are null, this returns null. Otherwise, it returns a
   /// non-null value. If one of the values is null, then the result is obtained
   /// by applying [scale] to the other value. If neither value is null and `t ==
   /// 0.0`, then `a` is returned unmodified; if `t == 1.0` then `b` is returned
   /// unmodified. Otherwise, the values are computed by interpolating the
   /// properties appropriately.
   ///
   /// {@macro dart.ui.shadow.lerp}
   ///
   /// See also:
   ///
   ///  * [Decoration.lerp], which can interpolate between any two types of
   ///    [Decoration]s, not just [BoxDecoration]s.
   ///  * [lerpFrom] and [lerpTo], which are used to implement [Decoration.lerp]
   ///    and which use [BoxDecoration.lerp] when interpolating two
   ///    [BoxDecoration]s or a [BoxDecoration] to or from null.
   static BoxDecoration? lerp(BoxDecoration? a, BoxDecoration? b, double t) {
     assert(t != null);
     if (a == null && b == null)
       return null;
     if (a == null)
       return b!.scale(t);
     if (b == null)
       return a.scale(1.0 - t);
     if (t == 0.0)
       return a;
     if (t == 1.0)
       return b;
     return BoxDecoration(
       color: Color.lerp(a.color, b.color, t),
       image: t < 0.5 ? a.image : b.image, // TODO(ianh): cross-fade the image
       border: BoxBorder.lerp(a.border, b.border, t),
       borderRadius: BorderRadiusGeometry.lerp(a.borderRadius, b.borderRadius, t),
       boxShadow: BoxShadow.lerpList(a.boxShadow, b.boxShadow, t),
       gradient: Gradient.lerp(a.gradient, b.gradient, t),
       shape: t < 0.5 ? a.shape : b.shape,
     );
   }

   @override
   bool operator ==(Object other) {
     if (identical(this, other))
       return true;
     if (other.runtimeType != runtimeType)
       return false;
     return other is BoxDecoration
         && other.color == color
         && other.image == image
         && other.border == border
         && other.borderRadius == borderRadius
         && listEquals<BoxShadow>(other.boxShadow, boxShadow)
         && other.gradient == gradient
         && other.shape == shape;
   }

   @override
   int get hashCode {
     return hashValues(
       color,
       image,
       border,
       borderRadius,
       hashList(boxShadow),
       gradient,
       shape,
     );
   }

   @override
   void debugFillProperties(DiagnosticPropertiesBuilder properties) {
     super.debugFillProperties(properties);
     properties
       ..defaultDiagnosticsTreeStyle = DiagnosticsTreeStyle.whitespace
       ..emptyBodyDescription = '<no decorations specified>';

     properties.add(ColorProperty('color', color, defaultValue: null));
     properties.add(DiagnosticsProperty<DecorationImage>('image', image, defaultValue: null));
     properties.add(DiagnosticsProperty<BoxBorder>('border', border, defaultValue: null));
     properties.add(DiagnosticsProperty<BorderRadiusGeometry>('borderRadius', borderRadius, defaultValue: null));
     properties.add(IterableProperty<BoxShadow>('boxShadow', boxShadow, defaultValue: null, style: DiagnosticsTreeStyle.whitespace));
     properties.add(DiagnosticsProperty<Gradient>('gradient', gradient, defaultValue: null));
     properties.add(EnumProperty<BoxShape>('shape', shape, defaultValue: BoxShape.rectangle));
   }

   @override
   bool hitTest(Size size, Offset position, { TextDirection? textDirection }) {
     assert(shape != null);
     assert((Offset.zero & size).contains(position));
     switch (shape) {
       case BoxShape.rectangle:
         if (borderRadius != null) {
           final RRect bounds = borderRadius!.resolve(textDirection).toRRect(Offset.zero & size);
           return bounds.contains(position);
         }
         return true;
       case BoxShape.circle:
         // Circles are inscribed into our smallest dimension.
         final Offset center = size.center(Offset.zero);
         final double distance = (position - center).distance;
         return distance <= math.min(size.width, size.height) / 2.0;
     }
   }

   @override
   BoxPainter createBoxPainter([ VoidCallback? onChanged ]) {
     assert(onChanged != null || image == null);
     return _BoxDecorationPainter(this, onChanged);
   }
 }

 /// An object that paints a [BoxDecoration] into a canvas.
 class _BoxDecorationPainter extends BoxPainter {
   _BoxDecorationPainter(this._decoration, VoidCallback? onChanged)
     : assert(_decoration != null),
       super(onChanged);

   final BoxDecoration _decoration;

   Paint? _cachedBackgroundPaint;
   Rect? _rectForCachedBackgroundPaint;
   Paint _getBackgroundPaint(Rect rect, TextDirection? textDirection) {
     assert(rect != null);
     assert(_decoration.gradient != null || _rectForCachedBackgroundPaint == null);

     if (_cachedBackgroundPaint == null ||
         (_decoration.gradient != null && _rectForCachedBackgroundPaint != rect)) {
       final Paint paint = Paint();
       if (_decoration.backgroundBlendMode != null)
         paint.blendMode = _decoration.backgroundBlendMode!;
       if (_decoration.color != null)
         paint.color = _decoration.color!;
       if (_decoration.gradient != null) {
         paint.shader = _decoration.gradient!.createShader(rect, textDirection: textDirection);
         _rectForCachedBackgroundPaint = rect;
       }
       _cachedBackgroundPaint = paint;
     }

     return _cachedBackgroundPaint!;
   }

   void _paintBox(Canvas canvas, Rect rect, Paint paint, TextDirection? textDirection) {
     switch (_decoration.shape) {
       case BoxShape.circle:
         assert(_decoration.borderRadius == null);
         final Offset center = rect.center;
         final double radius = rect.shortestSide / 2.0;
         canvas.drawCircle(center, radius, paint);
         break;
       case BoxShape.rectangle:
         if (_decoration.borderRadius == null) {
           canvas.drawRect(rect, paint);
         } else {
           canvas.drawRRect(_decoration.borderRadius!.resolve(textDirection).toRRect(rect), paint);
         }
         break;
     }
   }

   void _paintShadows(Canvas canvas, Rect rect, TextDirection? textDirection) {
     if (_decoration.boxShadow == null)
       return;
     for (final BoxShadow boxShadow in _decoration.boxShadow!) {
       final Paint paint = boxShadow.toPaint();
       final Rect bounds = rect.shift(boxShadow.offset).inflate(boxShadow.spreadRadius);
       _paintBox(canvas, bounds, paint, textDirection);
     }
   }

   void _paintBackgroundColor(Canvas canvas, Rect rect, TextDirection? textDirection) {
     if (_decoration.color != null || _decoration.gradient != null)
       _paintBox(canvas, rect, _getBackgroundPaint(rect, textDirection), textDirection);
   }

   DecorationImagePainter? _imagePainter;
   void _paintBackgroundImage(Canvas canvas, Rect rect, ImageConfiguration configuration) {
     if (_decoration.image == null)
       return;
     _imagePainter ??= _decoration.image!.createPainter(onChanged!);
     Path? clipPath;
     switch (_decoration.shape) {
       case BoxShape.circle:
         assert(_decoration.borderRadius == null);
         final Offset center = rect.center;
         final double radius = rect.shortestSide / 2.0;
         final Rect square = Rect.fromCircle(center: center, radius: radius);
         clipPath = Path()..addOval(square);
         break;
       case BoxShape.rectangle:
         if (_decoration.borderRadius != null)
           clipPath = Path()..addRRect(_decoration.borderRadius!.resolve(configuration.textDirection).toRRect(rect));
         break;
     }
     _imagePainter!.paint(canvas, rect, clipPath, configuration);
   }

   @override
   void dispose() {
     _imagePainter?.dispose();
     super.dispose();
   }

   /// Paint the box decoration into the given location on the given canvas.
   @override
   void paint(Canvas canvas, Offset offset, ImageConfiguration configuration) {
     assert(configuration != null);
     assert(configuration.size != null);
     final Rect rect = offset & configuration.size!;
     final TextDirection? textDirection = configuration.textDirection;
     _paintShadows(canvas, rect, textDirection);
     _paintBackgroundColor(canvas, rect, textDirection);
     _paintBackgroundImage(canvas, rect, configuration);
     _decoration.border?.paint(
       canvas,
       rect,
       shape: _decoration.shape,
       borderRadius: _decoration.borderRadius?.resolve(textDirection),
       textDirection: configuration.textDirection,
     );
   }

   @override
   String toString() {
     return 'BoxPainter for $_decoration';
   }
 }
	// Copyright 2014 The Flutter 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 'package:flutter/foundation.dart';

	import 'basic_types.dart';
	import 'border_radius.dart';
	import 'box_border.dart';
	import 'box_shadow.dart';
	import 'colors.dart';
	import 'decoration.dart';
	import 'decoration_image.dart';
	import 'edge_insets.dart';
	import 'gradient.dart';
	import 'image_provider.dart';

	/// An immutable description of how to paint a box.
	///
	/// The [BoxDecoration] class provides a variety of ways to draw a box.
	///
	/// The box has a [border], a body, and may cast a [boxShadow].
	///
	/// The [shape] of the box can be a circle or a rectangle. If it is a rectangle,
	/// then the [borderRadius] property controls the roundness of the corners.
	///
	/// The body of the box is painted in layers. The bottom-most layer is the
	/// [color], which fills the box. Above that is the [gradient], which also fills
	/// the box. Finally there is the [image], the precise alignment of which is
	/// controlled by the [DecorationImage] class.
	///
	/// The [border] paints over the body; the [boxShadow], naturally, paints below it.
	///
	/// {@tool snippet}
	///
	/// The following applies a [BoxDecoration] to a [Container] widget to draw an
	/// [image] of an owl with a thick black [border] and rounded corners.
	///
	/// ![](https://flutter.github.io/assets-for-api-docs/assets/painting/box_decoration.png)
	///
	/// ```dart
	/// Container(
	/// decoration: BoxDecoration(
	/// color: const Color(0xff7c94b6),
	/// image: const DecorationImage(
	/// image: NetworkImage('https://flutter.github.io/assets-for-api-docs/assets/widgets/owl-2.jpg'),
	/// fit: BoxFit.cover,
	/// ),
	/// border: Border.all(
	/// color: Colors.black,
	/// width: 8,
	/// ),
	/// borderRadius: BorderRadius.circular(12),
	/// ),
	/// )
	/// ```
	/// {@end-tool}
	///
	/// {@template flutter.painting.BoxDecoration.clip}
	/// The [shape] or the [borderRadius] won't clip the children of the
	/// decorated [Container]. If the clip is required, insert a clip widget
	/// (e.g., [ClipRect], [ClipRRect], [ClipPath]) as the child of the [Container].
	/// Be aware that clipping may be costly in terms of performance.
	/// {@endtemplate}
	///
	/// See also:
	///
	/// * [DecoratedBox] and [Container], widgets that can be configured with
	/// [BoxDecoration] objects.
	/// * [CustomPaint], a widget that lets you draw arbitrary graphics.
	/// * [Decoration], the base class which lets you define other decorations.
	class BoxDecoration extends Decoration {
	/// Creates a box decoration.
	///
	/// * If [color] is null, this decoration does not paint a background color.
	/// * If [image] is null, this decoration does not paint a background image.
	/// * If [border] is null, this decoration does not paint a border.
	/// * If [borderRadius] is null, this decoration uses more efficient background
	/// painting commands. The [borderRadius] argument must be null if [shape] is
	/// [BoxShape.circle].
	/// * If [boxShadow] is null, this decoration does not paint a shadow.
	/// * If [gradient] is null, this decoration does not paint gradients.
	/// * If [backgroundBlendMode] is null, this decoration paints with [BlendMode.srcOver]
	///
	/// The [shape] argument must not be null.
	const BoxDecoration({
	this.color,
	this.image,
	this.border,
	this.borderRadius,
	this.boxShadow,
	this.gradient,
	this.backgroundBlendMode,
	this.shape = BoxShape.rectangle,
	}) : assert(shape != null),
	assert(
	backgroundBlendMode == null \|\| color != null \|\| gradient != null,
	"backgroundBlendMode applies to BoxDecoration's background color or "
	'gradient, but no color or gradient was provided.',
	);

	/// Creates a copy of this object but with the given fields replaced with the
	/// new values.
	BoxDecoration copyWith({
	Color? color,
	DecorationImage? image,
	BoxBorder? border,
	BorderRadiusGeometry? borderRadius,
	List<BoxShadow>? boxShadow,
	Gradient? gradient,
	BlendMode? backgroundBlendMode,
	BoxShape? shape,
	}) {
	return BoxDecoration(
	color: color ?? this.color,
	image: image ?? this.image,
	border: border ?? this.border,
	borderRadius: borderRadius ?? this.borderRadius,
	boxShadow: boxShadow ?? this.boxShadow,
	gradient: gradient ?? this.gradient,
	backgroundBlendMode: backgroundBlendMode ?? this.backgroundBlendMode,
	shape: shape ?? this.shape,
	);
	}

	@override
	bool debugAssertIsValid() {
	assert(shape != BoxShape.circle \|\| borderRadius == null); // Can't have a border radius if you're a circle.
	return super.debugAssertIsValid();
	}

	/// The color to fill in the background of the box.
	///
	/// The color is filled into the [shape] of the box (e.g., either a rectangle,
	/// potentially with a [borderRadius], or a circle).
	///
	/// This is ignored if [gradient] is non-null.
	///
	/// The [color] is drawn under the [image].
	final Color? color;

	/// An image to paint above the background [color] or [gradient].
	///
	/// If [shape] is [BoxShape.circle] then the image is clipped to the circle's
	/// boundary; if [borderRadius] is non-null then the image is clipped to the
	/// given radii.
	final DecorationImage? image;

	/// A border to draw above the background [color], [gradient], or [image].
	///
	/// Follows the [shape] and [borderRadius].
	///
	/// Use [Border] objects to describe borders that do not depend on the reading
	/// direction.
	///
	/// Use [BoxBorder] objects to describe borders that should flip their left
	/// and right edges based on whether the text is being read left-to-right or
	/// right-to-left.
	final BoxBorder? border;

	/// If non-null, the corners of this box are rounded by this [BorderRadius].
	///
	/// Applies only to boxes with rectangular shapes; ignored if [shape] is not
	/// [BoxShape.rectangle].
	///
	/// {@macro flutter.painting.BoxDecoration.clip}
	final BorderRadiusGeometry? borderRadius;

	/// A list of shadows cast by this box behind the box.
	///
	/// The shadow follows the [shape] of the box.
	///
	/// See also:
	///
	/// * [kElevationToShadow], for some predefined shadows used in Material
	/// Design.
	/// * [PhysicalModel], a widget for showing shadows.
	final List<BoxShadow>? boxShadow;

	/// A gradient to use when filling the box.
	///
	/// If this is specified, [color] has no effect.
	///
	/// The [gradient] is drawn under the [image].
	final Gradient? gradient;

	/// The blend mode applied to the [color] or [gradient] background of the box.
	///
	/// If no [backgroundBlendMode] is provided then the default painting blend
	/// mode is used.
	///
	/// If no [color] or [gradient] is provided then the blend mode has no impact.
	final BlendMode? backgroundBlendMode;

	/// The shape to fill the background [color], [gradient], and [image] into and
	/// to cast as the [boxShadow].
	///
	/// If this is [BoxShape.circle] then [borderRadius] is ignored.
	///
	/// The [shape] cannot be interpolated; animating between two [BoxDecoration]s
	/// with different [shape]s will result in a discontinuity in the rendering.
	/// To interpolate between two shapes, consider using [ShapeDecoration] and
	/// different [ShapeBorder]s; in particular, [CircleBorder] instead of
	/// [BoxShape.circle] and [RoundedRectangleBorder] instead of
	/// [BoxShape.rectangle].
	///
	/// {@macro flutter.painting.BoxDecoration.clip}
	final BoxShape shape;

	@override
	EdgeInsetsGeometry? get padding => border?.dimensions;

	@override
	Path getClipPath(Rect rect, TextDirection textDirection) {
	switch (shape) {
	case BoxShape.circle:
	final Offset center = rect.center;
	final double radius = rect.shortestSide / 2.0;
	final Rect square = Rect.fromCircle(center: center, radius: radius);
	return Path()..addOval(square);
	case BoxShape.rectangle:
	if (borderRadius != null)
	return Path()..addRRect(borderRadius!.resolve(textDirection).toRRect(rect));
	return Path()..addRect(rect);
	}
	}

	/// Returns a new box decoration that is scaled by the given factor.
	BoxDecoration scale(double factor) {
	return BoxDecoration(
	color: Color.lerp(null, color, factor),
	image: image, // TODO(ianh): fade the image from transparent
	border: BoxBorder.lerp(null, border, factor),
	borderRadius: BorderRadiusGeometry.lerp(null, borderRadius, factor),
	boxShadow: BoxShadow.lerpList(null, boxShadow, factor),
	gradient: gradient?.scale(factor),
	shape: shape,
	);
	}

	@override
	bool get isComplex => boxShadow != null;

	@override
	BoxDecoration? lerpFrom(Decoration? a, double t) {
	if (a == null)
	return scale(t);
	if (a is BoxDecoration)
	return BoxDecoration.lerp(a, this, t);
	return super.lerpFrom(a, t) as BoxDecoration?;
	}

	@override
	BoxDecoration? lerpTo(Decoration? b, double t) {
	if (b == null)
	return scale(1.0 - t);
	if (b is BoxDecoration)
	return BoxDecoration.lerp(this, b, t);
	return super.lerpTo(b, t) as BoxDecoration?;
	}

	/// Linearly interpolate between two box decorations.
	///
	/// Interpolates each parameter of the box decoration separately.
	///
	/// The [shape] is not interpolated. To interpolate the shape, consider using
	/// a [ShapeDecoration] with different border shapes.
	///
	/// If both values are null, this returns null. Otherwise, it returns a
	/// non-null value. If one of the values is null, then the result is obtained
	/// by applying [scale] to the other value. If neither value is null and `t ==
	/// 0.0`, then `a` is returned unmodified; if `t == 1.0` then `b` is returned
	/// unmodified. Otherwise, the values are computed by interpolating the
	/// properties appropriately.
	///
	/// {@macro dart.ui.shadow.lerp}
	///
	/// See also:
	///
	/// * [Decoration.lerp], which can interpolate between any two types of
	/// [Decoration]s, not just [BoxDecoration]s.
	/// * [lerpFrom] and [lerpTo], which are used to implement [Decoration.lerp]
	/// and which use [BoxDecoration.lerp] when interpolating two
	/// [BoxDecoration]s or a [BoxDecoration] to or from null.
	static BoxDecoration? lerp(BoxDecoration? a, BoxDecoration? b, double t) {
	assert(t != null);
	if (a == null && b == null)
	return null;
	if (a == null)
	return b!.scale(t);
	if (b == null)
	return a.scale(1.0 - t);
	if (t == 0.0)
	return a;
	if (t == 1.0)
	return b;
	return BoxDecoration(
	color: Color.lerp(a.color, b.color, t),
	image: t < 0.5 ? a.image : b.image, // TODO(ianh): cross-fade the image
	border: BoxBorder.lerp(a.border, b.border, t),
	borderRadius: BorderRadiusGeometry.lerp(a.borderRadius, b.borderRadius, t),
	boxShadow: BoxShadow.lerpList(a.boxShadow, b.boxShadow, t),
	gradient: Gradient.lerp(a.gradient, b.gradient, t),
	shape: t < 0.5 ? a.shape : b.shape,
	);
	}

	@override
	bool operator ==(Object other) {
	if (identical(this, other))
	return true;
	if (other.runtimeType != runtimeType)
	return false;
	return other is BoxDecoration
	&& other.color == color
	&& other.image == image
	&& other.border == border
	&& other.borderRadius == borderRadius
	&& listEquals<BoxShadow>(other.boxShadow, boxShadow)
	&& other.gradient == gradient
	&& other.shape == shape;
	}

	@override
	int get hashCode {
	return hashValues(
	color,
	image,
	border,
	borderRadius,
	hashList(boxShadow),
	gradient,
	shape,
	);
	}

	@override
	void debugFillProperties(DiagnosticPropertiesBuilder properties) {
	super.debugFillProperties(properties);
	properties
	..defaultDiagnosticsTreeStyle = DiagnosticsTreeStyle.whitespace
	..emptyBodyDescription = '<no decorations specified>';

	properties.add(ColorProperty('color', color, defaultValue: null));
	properties.add(DiagnosticsProperty<DecorationImage>('image', image, defaultValue: null));
	properties.add(DiagnosticsProperty<BoxBorder>('border', border, defaultValue: null));
	properties.add(DiagnosticsProperty<BorderRadiusGeometry>('borderRadius', borderRadius, defaultValue: null));
	properties.add(IterableProperty<BoxShadow>('boxShadow', boxShadow, defaultValue: null, style: DiagnosticsTreeStyle.whitespace));
	properties.add(DiagnosticsProperty<Gradient>('gradient', gradient, defaultValue: null));
	properties.add(EnumProperty<BoxShape>('shape', shape, defaultValue: BoxShape.rectangle));
	}

	@override
	bool hitTest(Size size, Offset position, { TextDirection? textDirection }) {
	assert(shape != null);
	assert((Offset.zero & size).contains(position));
	switch (shape) {
	case BoxShape.rectangle:
	if (borderRadius != null) {
	final RRect bounds = borderRadius!.resolve(textDirection).toRRect(Offset.zero & size);
	return bounds.contains(position);
	}
	return true;
	case BoxShape.circle:
	// Circles are inscribed into our smallest dimension.
	final Offset center = size.center(Offset.zero);
	final double distance = (position - center).distance;
	return distance <= math.min(size.width, size.height) / 2.0;
	}
	}

	@override
	BoxPainter createBoxPainter([ VoidCallback? onChanged ]) {
	assert(onChanged != null \|\| image == null);
	return _BoxDecorationPainter(this, onChanged);
	}
	}

	/// An object that paints a [BoxDecoration] into a canvas.
	class _BoxDecorationPainter extends BoxPainter {
	_BoxDecorationPainter(this._decoration, VoidCallback? onChanged)
	: assert(_decoration != null),
	super(onChanged);

	final BoxDecoration _decoration;

	Paint? _cachedBackgroundPaint;
	Rect? _rectForCachedBackgroundPaint;
	Paint _getBackgroundPaint(Rect rect, TextDirection? textDirection) {
	assert(rect != null);
	assert(_decoration.gradient != null \|\| _rectForCachedBackgroundPaint == null);

	if (_cachedBackgroundPaint == null \|\|
	(_decoration.gradient != null && _rectForCachedBackgroundPaint != rect)) {
	final Paint paint = Paint();
	if (_decoration.backgroundBlendMode != null)
	paint.blendMode = _decoration.backgroundBlendMode!;
	if (_decoration.color != null)
	paint.color = _decoration.color!;
	if (_decoration.gradient != null) {
	paint.shader = _decoration.gradient!.createShader(rect, textDirection: textDirection);
	_rectForCachedBackgroundPaint = rect;
	}
	_cachedBackgroundPaint = paint;
	}

	return _cachedBackgroundPaint!;
	}

	void _paintBox(Canvas canvas, Rect rect, Paint paint, TextDirection? textDirection) {
	switch (_decoration.shape) {
	case BoxShape.circle:
	assert(_decoration.borderRadius == null);
	final Offset center = rect.center;
	final double radius = rect.shortestSide / 2.0;
	canvas.drawCircle(center, radius, paint);
	break;
	case BoxShape.rectangle:
	if (_decoration.borderRadius == null) {
	canvas.drawRect(rect, paint);
	} else {
	canvas.drawRRect(_decoration.borderRadius!.resolve(textDirection).toRRect(rect), paint);
	}
	break;
	}
	}

	void _paintShadows(Canvas canvas, Rect rect, TextDirection? textDirection) {
	if (_decoration.boxShadow == null)
	return;
	for (final BoxShadow boxShadow in _decoration.boxShadow!) {
	final Paint paint = boxShadow.toPaint();
	final Rect bounds = rect.shift(boxShadow.offset).inflate(boxShadow.spreadRadius);
	_paintBox(canvas, bounds, paint, textDirection);
	}
	}

	void _paintBackgroundColor(Canvas canvas, Rect rect, TextDirection? textDirection) {
	if (_decoration.color != null \|\| _decoration.gradient != null)
	_paintBox(canvas, rect, _getBackgroundPaint(rect, textDirection), textDirection);
	}

	DecorationImagePainter? _imagePainter;
	void _paintBackgroundImage(Canvas canvas, Rect rect, ImageConfiguration configuration) {
	if (_decoration.image == null)
	return;
	_imagePainter ??= _decoration.image!.createPainter(onChanged!);
	Path? clipPath;
	switch (_decoration.shape) {
	case BoxShape.circle:
	assert(_decoration.borderRadius == null);
	final Offset center = rect.center;
	final double radius = rect.shortestSide / 2.0;
	final Rect square = Rect.fromCircle(center: center, radius: radius);
	clipPath = Path()..addOval(square);
	break;
	case BoxShape.rectangle:
	if (_decoration.borderRadius != null)
	clipPath = Path()..addRRect(_decoration.borderRadius!.resolve(configuration.textDirection).toRRect(rect));
	break;
	}
	_imagePainter!.paint(canvas, rect, clipPath, configuration);
	}

	@override
	void dispose() {
	_imagePainter?.dispose();
	super.dispose();
	}

	/// Paint the box decoration into the given location on the given canvas.
	@override
	void paint(Canvas canvas, Offset offset, ImageConfiguration configuration) {
	assert(configuration != null);
	assert(configuration.size != null);
	final Rect rect = offset & configuration.size!;
	final TextDirection? textDirection = configuration.textDirection;
	_paintShadows(canvas, rect, textDirection);
	_paintBackgroundColor(canvas, rect, textDirection);
	_paintBackgroundImage(canvas, rect, configuration);
	_decoration.border?.paint(
	canvas,
	rect,
	shape: _decoration.shape,
	borderRadius: _decoration.borderRadius?.resolve(textDirection),
	textDirection: configuration.textDirection,
	);
	}

	@override
	String toString() {
	return 'BoxPainter for $_decoration';
	}
	}