// Copyright 2013 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.
part of dart.ui;

// Examples can assume:
// // (for the example in Color)
// // ignore_for_file: use_full_hex_values_for_flutter_colors
// late ui.Image _image;
// dynamic _cacheImage(dynamic _, [dynamic _]) { }
// dynamic _drawImage(dynamic _, [dynamic _]) { }

// Some methods in this file assert that their arguments are not null. These
// asserts are just to improve the error messages; they should only cover
// arguments that are either dereferenced _in Dart_, before being passed to the
// engine, or that the engine explicitly null-checks itself (after attempting to
// convert the argument to a native type). It should not be possible for a null
// or invalid value to be used by the engine even in release mode, since that
// would cause a crash. It is, however, acceptable for error messages to be much
// less useful or correct in release mode than in debug mode.
//
// Painting APIs will also warn about arguments representing NaN coordinates,
// which can not be rendered by Skia.

bool _rectIsValid(Rect rect) {
  assert(!rect.hasNaN, 'Rect argument contained a NaN value.');
  return true;
}

bool _rrectIsValid(RRect rrect) {
  assert(!rrect.hasNaN, 'RRect argument contained a NaN value.');
  return true;
}

bool _rsuperellipseIsValid(RSuperellipse rsuperellipse) {
  assert(!rsuperellipse.hasNaN, 'RSuperellipse argument contained a NaN value.');
  return true;
}

bool _offsetIsValid(Offset offset) {
  assert(!offset.dx.isNaN && !offset.dy.isNaN, 'Offset argument contained a NaN value.');
  return true;
}

bool _matrix4IsValid(Float64List matrix4) {
  assert(matrix4.length == 16, 'Matrix4 must have 16 entries.');
  assert(matrix4.every((double value) => value.isFinite), 'Matrix4 entries must be finite.');
  return true;
}

bool _radiusIsValid(Radius radius) {
  assert(!radius.x.isNaN && !radius.y.isNaN, 'Radius argument contained a NaN value.');
  return true;
}

Color _scaleAlpha(Color x, double factor) {
  return x.withValues(alpha: clampDouble(x.a * factor, 0, 1));
}

ColorSpace _widerColorSpace(ColorSpace a, ColorSpace b) {
  return a == ColorSpace.displayP3 || b == ColorSpace.displayP3 ? ColorSpace.displayP3 : a;
}

/// An immutable color value in ARGB format.
///
/// Consider the light teal of the [Flutter logo](https://flutter.dev/brand). It
/// is fully opaque, with a red [r] channel value of `0.2588` (or `0x42` or `66`
/// as an 8-bit value), a green [g] channel value of `0.6471` (or `0xA5` or
/// `165` as an 8-bit value), and a blue [b] channel value of `0.9608` (or
/// `0xF5` or `245` as an 8-bit value). In a common [CSS hex color syntax](https://developer.mozilla.org/en-US/docs/Web/CSS/hex-color)
/// for RGB color values, it would be described as `#42A5F5`.
///
/// Here are some ways it could be constructed:
///
/// ```dart
/// const Color c1 = Color.from(alpha: 1.0, red: 0.2588, green: 0.6471, blue: 0.9608);
/// const Color c2 = Color(0xFF42A5F5);
/// const Color c3 = Color.fromARGB(0xFF, 0x42, 0xA5, 0xF5);
/// const Color c4 = Color.fromARGB(255, 66, 165, 245);
/// const Color c5 = Color.fromRGBO(66, 165, 245, 1.0);
/// ```
///
/// If you are having a problem with [Color.new] wherein it seems your color is
/// just not painting, check to make sure you are specifying the full 8
/// hexadecimal digits. If you only specify six, then the leading two digits are
/// assumed to be zero, which means fully-transparent:
///
/// ```dart
/// const Color c1 = Color(0xFFFFFF); // fully transparent white (invisible)
/// const Color c2 = Color(0xFFFFFFFF); // fully opaque white (visible)
///
/// // Or use double-based channel values:
/// const Color c3 = Color.from(alpha: 1.0, red: 1.0, green: 1.0, blue: 1.0);
/// ```
///
/// [Color]'s color components are stored as floating-point values. Care should
/// be taken if one does not want the literal equality provided by `operator==`.
/// To test equality inside of Flutter tests consider using [`isSameColorAs`][].
///
/// See also:
///
///  * [Colors](https://api.flutter.dev/flutter/material/Colors-class.html),
///    which defines the colors found in the Material Design specification.
///  * [`isSameColorAs`][],
///    a Matcher to handle floating-point deltas when checking [Color] equality.
///
/// [`isSameColorAs`]: https://api.flutter.dev/flutter/flutter_test/isSameColorAs.html
class Color {
  /// Construct an [ColorSpace.sRGB] color from the lower 32 bits of an [int].
  ///
  /// The bits are interpreted as follows:
  ///
  /// * Bits 24-31 are the alpha value.
  /// * Bits 16-23 are the red value.
  /// * Bits 8-15 are the green value.
  /// * Bits 0-7 are the blue value.
  ///
  /// In other words, if AA is the alpha value in hex, RR the red value in hex,
  /// GG the green value in hex, and BB the blue value in hex, a color can be
  /// expressed as `Color(0xAARRGGBB)`.
  ///
  /// For example, to get a fully opaque orange, you would use `const
  /// Color(0xFFFF9000)` (`FF` for the alpha, `FF` for the red, `90` for the
  /// green, and `00` for the blue).
  ///
  /// {@template dart.ui.Color.componentsStoredAsFloatingPoint}
  /// > [!NOTE]
  /// > Each color is stored as floating-point color components, where the final
  /// > value of each component is approximated by storing `c / 255`, where `c`
  /// is one of the four components (alpha, red, green, blue).
  /// {@endtemplate}
  const Color(int value)
    : this._fromARGBC(value >> 24, value >> 16, value >> 8, value, ColorSpace.sRGB);

  /// Construct a color with floating-point color components.
  ///
  /// Color components allows arbitrary bit depths for color components to be be
  /// supported. The values are interpreted relative to the [ColorSpace]
  /// argument.
  ///
  /// ## Example
  ///
  /// ```dart
  /// // Fully opaque maximum red color
  /// const Color c1 = Color.from(alpha: 1.0, red: 1.0, green: 0.0, blue: 0.0);
  ///
  /// // Partially transparent moderately blue and green color
  /// const Color c2 = Color.from(alpha: 0.5, red: 0.0, green: 0.5, blue: 0.5);
  ///
  /// // Fully transparent color
  /// const Color c3 = Color.from(alpha: 0.0, red: 0.0, green: 0.0, blue: 0.0);
  /// ```
  const Color.from({
    required double alpha,
    required double red,
    required double green,
    required double blue,
    this.colorSpace = ColorSpace.sRGB,
  }) : a = alpha,
       r = red,
       g = green,
       b = blue;

  /// Construct an sRGB color from the lower 8 bits of four integers.
  ///
  /// * `a` is the alpha value, with 0 being transparent and 255 being fully
  ///   opaque.
  /// * `r` is [red], from 0 to 255.
  /// * `g` is [green], from 0 to 255.
  /// * `b` is [blue], from 0 to 255.
  ///
  /// Out of range values are brought into range using modulo 255.
  ///
  /// See also [fromRGBO], which takes the alpha value as a floating point
  /// value.
  ///
  /// {@macro dart.ui.Color.componentsStoredAsFloatingPoint}
  const Color.fromARGB(int a, int r, int g, int b) : this._fromARGBC(a, r, g, b, ColorSpace.sRGB);

  const Color._fromARGBC(int alpha, int red, int green, int blue, ColorSpace colorSpace)
    : this._fromRGBOC(red, green, blue, (alpha & 0xff) / 255, colorSpace);

  /// Create an sRGB color from red, green, blue, and opacity, similar to
  /// `rgba()` in CSS.
  ///
  /// * `r` is [red], from 0 to 255.
  /// * `g` is [green], from 0 to 255.
  /// * `b` is [blue], from 0 to 255.
  /// * `opacity` is alpha channel of this color as a double, with 0.0 being
  ///   transparent and 1.0 being fully opaque.
  ///
  /// Out of range values are brought into range using modulo 255.
  ///
  /// See also [fromARGB], which takes the opacity as an integer value.
  ///
  /// {@macro dart.ui.Color.componentsStoredAsFloatingPoint}
  const Color.fromRGBO(int r, int g, int b, double opacity)
    : this._fromRGBOC(r, g, b, opacity, ColorSpace.sRGB);

  const Color._fromRGBOC(int r, int g, int b, double opacity, this.colorSpace)
    : a = opacity,
      r = (r & 0xff) / 255,
      g = (g & 0xff) / 255,
      b = (b & 0xff) / 255;

  /// The alpha channel of this color.
  final double a;

  /// The red channel of this color.
  final double r;

  /// The green channel of this color.
  final double g;

  /// The blue channel of this color.
  final double b;

  /// The color space of this color.
  final ColorSpace colorSpace;

  static int _floatToInt8(double x) {
    return (x * 255.0).round().clamp(0, 255);
  }

  /// A 32 bit value representing this color.
  ///
  /// This getter is a _stub_. It is recommended instead to use the explicit
  /// [toARGB32] method.
  @Deprecated('Use component accessors like .r or .g, or toARGB32 for an explicit conversion')
  int get value => toARGB32();

  /// Returns a 32-bit value representing this color.
  ///
  /// The returned value is compatible with the default constructor
  /// ([Color.new]) but does _not_ guarantee to result in the same color due to
  /// [imprecisions in numeric conversions](https://en.wikipedia.org/wiki/Floating-point_error_mitigation).
  ///
  /// Unlike accessing the floating point equivalent channels individually
  /// ([a], [r], [g], [b]), this method is intentionally _lossy_, and scales
  /// each channel using `(channel * 255.0).round().clamp(0, 255)`.
  ///
  /// While useful for storing a 32-bit integer value, prefer accessing the
  /// individual channels (and storing the double equivalent) where higher
  /// precision is required.
  ///
  /// The bits are assigned as follows:
  ///
  /// * Bits 24-31 represents the [a] channel as an 8-bit unsigned integer.
  /// * Bits 16-23 represents the [r] channel as an 8-bit unsigned integer.
  /// * Bits 8-15 represents the [g] channel as an 8-bit unsigned integer.
  /// * Bits 0-7 represents the [b] channel as an 8-bit unsigned integer.
  ///
  /// > [!WARNING]
  /// > The value returned by this getter implicitly converts floating-point
  /// > component values (such as `0.5`) into their 8-bit equivalent by using
  /// > the [toARGB32] method; the returned value is not guaranteed to be stable
  /// > across different platforms or executions due to the complexity of
  /// > floating-point math.
  int toARGB32() {
    return _floatToInt8(a) << 24 |
        _floatToInt8(r) << 16 |
        _floatToInt8(g) << 8 |
        _floatToInt8(b) << 0;
  }

  /// The alpha channel of this color in an 8 bit value.
  ///
  /// A value of 0 means this color is fully transparent. A value of 255 means
  /// this color is fully opaque.
  @Deprecated('Use (*.a * 255.0).round().clamp(0, 255)')
  int get alpha => (0xff000000 & value) >> 24;

  /// The alpha channel of this color as a double.
  ///
  /// A value of 0.0 means this color is fully transparent. A value of 1.0 means
  /// this color is fully opaque.
  @Deprecated('Use .a.')
  double get opacity => alpha / 0xFF;

  /// The red channel of this color in an 8 bit value.
  @Deprecated('Use (*.r * 255.0).round().clamp(0, 255)')
  int get red => (0x00ff0000 & value) >> 16;

  /// The green channel of this color in an 8 bit value.
  @Deprecated('Use (*.g * 255.0).round().clamp(0, 255)')
  int get green => (0x0000ff00 & value) >> 8;

  /// The blue channel of this color in an 8 bit value.
  @Deprecated('Use (*.b * 255.0).round().clamp(0, 255)')
  int get blue => (0x000000ff & value) >> 0;

  /// Returns a new color with the provided components updated.
  ///
  /// Each component ([alpha], [red], [green], [blue]) represents a
  /// floating-point value; see [Color.from] for details and examples.
  ///
  /// If [colorSpace] is provided, and is different than the current color
  /// space, the component values are updated before transforming them to the
  /// provided [ColorSpace].
  ///
  /// Example:
  /// ```dart
  /// import 'dart:ui';
  /// /// Create a color with 50% opacity.
  /// Color makeTransparent(Color color) => color.withValues(alpha: 0.5);
  /// ```
  Color withValues({
    double? alpha,
    double? red,
    double? green,
    double? blue,
    ColorSpace? colorSpace,
  }) {
    Color? updatedComponents;
    if (alpha != null || red != null || green != null || blue != null) {
      updatedComponents = Color.from(
        alpha: alpha ?? a,
        red: red ?? r,
        green: green ?? g,
        blue: blue ?? b,
        colorSpace: this.colorSpace,
      );
    }
    if (colorSpace != null && colorSpace != this.colorSpace) {
      final _ColorTransform transform = _getColorTransform(this.colorSpace, colorSpace);
      return transform.transform(updatedComponents ?? this, colorSpace);
    } else {
      return updatedComponents ?? this;
    }
  }

  /// Returns a new color that matches this color with the alpha channel
  /// replaced with `a` (which ranges from 0 to 255).
  ///
  /// Out of range values will have unexpected effects.
  Color withAlpha(int a) {
    return Color.fromARGB(a, red, green, blue);
  }

  /// Returns a new color that matches this color with the alpha channel
  /// replaced with the given `opacity` (which ranges from 0.0 to 1.0).
  ///
  /// Out of range values will have unexpected effects.
  @Deprecated('Use .withValues() to avoid precision loss.')
  Color withOpacity(double opacity) {
    assert(opacity >= 0.0 && opacity <= 1.0);
    return withAlpha((255.0 * opacity).round());
  }

  /// Returns a new color that matches this color with the red channel replaced
  /// with `r` (which ranges from 0 to 255).
  ///
  /// Out of range values will have unexpected effects.
  Color withRed(int r) {
    return Color.fromARGB(alpha, r, green, blue);
  }

  /// Returns a new color that matches this color with the green channel
  /// replaced with `g` (which ranges from 0 to 255).
  ///
  /// Out of range values will have unexpected effects.
  Color withGreen(int g) {
    return Color.fromARGB(alpha, red, g, blue);
  }

  /// Returns a new color that matches this color with the blue channel replaced
  /// with `b` (which ranges from 0 to 255).
  ///
  /// Out of range values will have unexpected effects.
  Color withBlue(int b) {
    return Color.fromARGB(alpha, red, green, b);
  }

  // See <https://www.w3.org/TR/WCAG20/#relativeluminancedef>
  static double _linearizeColorComponent(double component) {
    if (component <= 0.03928) {
      return component / 12.92;
    }
    return math.pow((component + 0.055) / 1.055, 2.4) as double;
  }

  /// Returns a brightness value between 0 for darkest and 1 for lightest.
  ///
  /// Represents the relative luminance of the color. This value is computationally
  /// expensive to calculate.
  ///
  /// See <https://en.wikipedia.org/wiki/Relative_luminance>.
  double computeLuminance() {
    assert(colorSpace != ColorSpace.extendedSRGB);
    // See <https://www.w3.org/TR/WCAG20/#relativeluminancedef>
    final double R = _linearizeColorComponent(r);
    final double G = _linearizeColorComponent(g);
    final double B = _linearizeColorComponent(b);
    return 0.2126 * R + 0.7152 * G + 0.0722 * B;
  }

  /// Linearly interpolate between two colors.
  ///
  /// This is intended to be fast but as a result may be ugly. Consider
  /// [HSVColor] or writing custom logic for interpolating colors.
  ///
  /// If either color is null, this function linearly interpolates from a
  /// transparent instance of the other color. This is usually preferable to
  /// interpolating from [material.Colors.transparent] (`const
  /// Color(0x00000000)`), which is specifically transparent _black_.
  ///
  /// The `t` argument represents position on the timeline, with 0.0 meaning
  /// that the interpolation has not started, returning `a` (or something
  /// equivalent to `a`), 1.0 meaning that the interpolation has finished,
  /// returning `b` (or something equivalent to `b`), and values in between
  /// meaning that the interpolation is at the relevant point on the timeline
  /// between `a` and `b`. The interpolation can be extrapolated beyond 0.0 and
  /// 1.0, so negative values and values greater than 1.0 are valid (and can
  /// easily be generated by curves such as [Curves.elasticInOut]). Each channel
  /// will be clamped to the range 0 to 255.
  ///
  /// Values for `t` are usually obtained from an [Animation<double>], such as
  /// an [AnimationController].
  ///
  /// If the two colors are in different color spaces, both are converted to
  /// the wider gamut color space before interpolating. The result will be in
  /// the wider gamut color space. For example, interpolating between an sRGB
  /// color and a Display P3 color will produce a Display P3 result.
  static Color? lerp(Color? x, Color? y, double t) {
    assert(x?.colorSpace != ColorSpace.extendedSRGB);
    assert(y?.colorSpace != ColorSpace.extendedSRGB);
    if (y == null) {
      if (x == null) {
        return null;
      } else {
        return _scaleAlpha(x, 1.0 - t);
      }
    } else {
      if (x == null) {
        return _scaleAlpha(y, t);
      } else {
        final Color a;
        final Color b;
        final ColorSpace resultColorSpace;
        if (x.colorSpace == y.colorSpace) {
          a = x;
          b = y;
          resultColorSpace = x.colorSpace;
        } else {
          resultColorSpace = _widerColorSpace(x.colorSpace, y.colorSpace);
          a = x.withValues(colorSpace: resultColorSpace);
          b = y.withValues(colorSpace: resultColorSpace);
        }
        return Color.from(
          alpha: clampDouble(_lerpDouble(a.a, b.a, t), 0, 1),
          red: clampDouble(_lerpDouble(a.r, b.r, t), 0, 1),
          green: clampDouble(_lerpDouble(a.g, b.g, t), 0, 1),
          blue: clampDouble(_lerpDouble(a.b, b.b, t), 0, 1),
          colorSpace: resultColorSpace,
        );
      }
    }
  }

  /// Combine the foreground color as a transparent color over top
  /// of a background color, and return the resulting combined color.
  ///
  /// This uses standard alpha blending ("SRC over DST") rules to produce a
  /// blended color from two colors. This can be used as a performance
  /// enhancement when trying to avoid needless alpha blending compositing
  /// operations for two things that are solid colors with the same shape, but
  /// overlay each other: instead, just paint one with the combined color.
  static Color alphaBlend(Color foreground, Color background) {
    assert(foreground.colorSpace == background.colorSpace);
    assert(foreground.colorSpace != ColorSpace.extendedSRGB);
    final double alpha = foreground.a;
    if (alpha == 0) {
      // Foreground completely transparent.
      return background;
    }
    final double invAlpha = 1 - alpha;
    double backAlpha = background.a;
    if (backAlpha == 1) {
      // Opaque background case
      return Color.from(
        alpha: 1,
        red: alpha * foreground.r + invAlpha * background.r,
        green: alpha * foreground.g + invAlpha * background.g,
        blue: alpha * foreground.b + invAlpha * background.b,
        colorSpace: foreground.colorSpace,
      );
    } else {
      // General case
      backAlpha = backAlpha * invAlpha;
      final double outAlpha = alpha + backAlpha;
      assert(outAlpha != 0);
      return Color.from(
        alpha: outAlpha,
        red: (foreground.r * alpha + background.r * backAlpha) / outAlpha,
        green: (foreground.g * alpha + background.g * backAlpha) / outAlpha,
        blue: (foreground.b * alpha + background.b * backAlpha) / outAlpha,
        colorSpace: foreground.colorSpace,
      );
    }
  }

  /// Returns an alpha value representative of the provided [opacity] value.
  ///
  /// The [opacity] value may not be null.
  static int getAlphaFromOpacity(double opacity) {
    return (clampDouble(opacity, 0.0, 1.0) * 255).round();
  }

  @override
  bool operator ==(Object other) {
    if (identical(this, other)) {
      return true;
    }
    if (other.runtimeType != runtimeType) {
      return false;
    }
    return other is Color &&
        other.a == a &&
        other.r == r &&
        other.g == g &&
        other.b == b &&
        other.colorSpace == colorSpace;
  }

  @override
  int get hashCode => Object.hash(a, r, g, b, colorSpace);

  @override
  String toString() =>
      'Color(alpha: ${a.toStringAsFixed(4)}, red: ${r.toStringAsFixed(4)}, green: ${g.toStringAsFixed(4)}, blue: ${b.toStringAsFixed(4)}, colorSpace: $colorSpace)';
}

/// Algorithms to use when painting on the canvas.
///
/// When drawing a shape or image onto a canvas, different algorithms can be
/// used to blend the pixels. The different values of [BlendMode] specify
/// different such algorithms.
///
/// Each algorithm has two inputs, the _source_, which is the image being drawn,
/// and the _destination_, which is the image into which the source image is
/// being composited. The destination is often thought of as the _background_.
/// The source and destination both have four color channels, the red, green,
/// blue, and alpha channels. These are typically represented as numbers in the
/// range 0.0 to 1.0. The output of the algorithm also has these same four
/// channels, with values computed from the source and destination.
///
/// The documentation of each value below describes how the algorithm works. In
/// each case, an image shows the output of blending a source image with a
/// destination image. In the images below, the destination is represented by an
/// image with horizontal lines and an opaque landscape photograph, and the
/// source is represented by an image with vertical lines (the same lines but
/// rotated) and a bird clip-art image. The [src] mode shows only the source
/// image, and the [dst] mode shows only the destination image. In the
/// documentation below, the transparency is illustrated by a checkerboard
/// pattern. The [clear] mode drops both the source and destination, resulting
/// in an output that is entirely transparent (illustrated by a solid
/// checkerboard pattern).
///
/// The horizontal and vertical bars in these images show the red, green, and
/// blue channels with varying opacity levels, then all three color channels
/// together with those same varying opacity levels, then all three color
/// channels set to zero with those varying opacity levels, then two bars showing
/// a red/green/blue repeating gradient, the first with full opacity and the
/// second with partial opacity, and finally a bar with the three color channels
/// set to zero but the opacity varying in a repeating gradient.
///
/// ## Application to the [Canvas] API
///
/// When using [Canvas.saveLayer] and [Canvas.restore], the blend mode of the
/// [Paint] given to the [Canvas.saveLayer] will be applied when
/// [Canvas.restore] is called. Each call to [Canvas.saveLayer] introduces a new
/// layer onto which shapes and images are painted; when [Canvas.restore] is
/// called, that layer is then composited onto the parent layer, with the source
/// being the most-recently-drawn shapes and images, and the destination being
/// the parent layer. (For the first [Canvas.saveLayer] call, the parent layer
/// is the canvas itself.)
///
/// See also:
///
///  * [Paint.blendMode], which uses [BlendMode] to define the compositing
///    strategy.
enum BlendMode {
  // This list comes from Skia's SkXfermode.h and the values (order) should be
  // kept in sync.
  // See: https://skia.org/docs/user/api/skpaint_overview/#SkXfermode

  /// Drop both the source and destination images, leaving nothing.
  ///
  /// This corresponds to the "clear" Porter-Duff operator.
  ///
  /// ![](https://flutter.github.io/assets-for-api-docs/assets/dart-ui/blend_mode_clear.png)
  clear,

  /// Drop the destination image, only paint the source image.
  ///
  /// Conceptually, the destination is first cleared, then the source image is
  /// painted.
  ///
  /// This corresponds to the "Copy" Porter-Duff operator.
  ///
  /// ![](https://flutter.github.io/assets-for-api-docs/assets/dart-ui/blend_mode_src.png)
  src,

  /// Drop the source image, only paint the destination image.
  ///
  /// Conceptually, the source image is discarded, leaving the destination
  /// untouched.
  ///
  /// This corresponds to the "Destination" Porter-Duff operator.
  ///
  /// ![](https://flutter.github.io/assets-for-api-docs/assets/dart-ui/blend_mode_dst.png)
  dst,

  /// Composite the source image over the destination image.
  ///
  /// This is the default value. It represents the most intuitive case, where
  /// shapes are painted on top of what is below, with transparent areas showing
  /// the destination layer.
  ///
  /// This corresponds to the "Source over Destination" Porter-Duff operator,
  /// also known as the Painter's Algorithm.
  ///
  /// ![](https://flutter.github.io/assets-for-api-docs/assets/dart-ui/blend_mode_srcOver.png)
  srcOver,

  /// Composite the source image under the destination image.
  ///
  /// This is the opposite of [srcOver].
  ///
  /// This corresponds to the "Destination over Source" Porter-Duff operator.
  ///
  /// ![](https://flutter.github.io/assets-for-api-docs/assets/dart-ui/blend_mode_dstOver.png)
  ///
  /// This is useful when the source image should have been painted before the
  /// destination image, but could not be.
  dstOver,

  /// Show the source image, but only where the two images overlap. The
  /// destination image is not rendered, it is treated merely as a mask. The
  /// color channels of the destination are ignored, only the opacity has an
  /// effect.
  ///
  /// To show the destination image instead, consider [dstIn].
  ///
  /// To reverse the semantic of the mask (only showing the source where the
  /// destination is absent, rather than where it is present), consider
  /// [srcOut].
  ///
  /// This corresponds to the "Source in Destination" Porter-Duff operator.
  ///
  /// ![](https://flutter.github.io/assets-for-api-docs/assets/dart-ui/blend_mode_srcIn.png)
  srcIn,

  /// Show the destination image, but only where the two images overlap. The
  /// source image is not rendered, it is treated merely as a mask. The color
  /// channels of the source are ignored, only the opacity has an effect.
  ///
  /// To show the source image instead, consider [srcIn].
  ///
  /// To reverse the semantic of the mask (only showing the source where the
  /// destination is present, rather than where it is absent), consider [dstOut].
  ///
  /// This corresponds to the "Destination in Source" Porter-Duff operator.
  ///
  /// ![](https://flutter.github.io/assets-for-api-docs/assets/dart-ui/blend_mode_dstIn.png)
  dstIn,

  /// Show the source image, but only where the two images do not overlap. The
  /// destination image is not rendered, it is treated merely as a mask. The color
  /// channels of the destination are ignored, only the opacity has an effect.
  ///
  /// To show the destination image instead, consider [dstOut].
  ///
  /// To reverse the semantic of the mask (only showing the source where the
  /// destination is present, rather than where it is absent), consider [srcIn].
  ///
  /// This corresponds to the "Source out Destination" Porter-Duff operator.
  ///
  /// ![](https://flutter.github.io/assets-for-api-docs/assets/dart-ui/blend_mode_srcOut.png)
  srcOut,

  /// Show the destination image, but only where the two images do not overlap. The
  /// source image is not rendered, it is treated merely as a mask. The color
  /// channels of the source are ignored, only the opacity has an effect.
  ///
  /// To show the source image instead, consider [srcOut].
  ///
  /// To reverse the semantic of the mask (only showing the destination where the
  /// source is present, rather than where it is absent), consider [dstIn].
  ///
  /// This corresponds to the "Destination out Source" Porter-Duff operator.
  ///
  /// ![](https://flutter.github.io/assets-for-api-docs/assets/dart-ui/blend_mode_dstOut.png)
  dstOut,

  /// Composite the source image over the destination image, but only where it
  /// overlaps the destination.
  ///
  /// This corresponds to the "Source atop Destination" Porter-Duff operator.
  ///
  /// This is essentially the [srcOver] operator, but with the output's opacity
  /// channel being set to that of the destination image instead of being a
  /// combination of both image's opacity channels.
  ///
  /// For a variant with the destination on top instead of the source, see
  /// [dstATop].
  ///
  /// ![](https://flutter.github.io/assets-for-api-docs/assets/dart-ui/blend_mode_srcATop.png)
  srcATop,

  /// Composite the destination image over the source image, but only where it
  /// overlaps the source.
  ///
  /// This corresponds to the "Destination atop Source" Porter-Duff operator.
  ///
  /// This is essentially the [dstOver] operator, but with the output's opacity
  /// channel being set to that of the source image instead of being a
  /// combination of both image's opacity channels.
  ///
  /// For a variant with the source on top instead of the destination, see
  /// [srcATop].
  ///
  /// ![](https://flutter.github.io/assets-for-api-docs/assets/dart-ui/blend_mode_dstATop.png)
  dstATop,

  /// Apply a bitwise `xor` operator to the source and destination images. This
  /// leaves transparency where they would overlap.
  ///
  /// This corresponds to the "Source xor Destination" Porter-Duff operator.
  ///
  /// ![](https://flutter.github.io/assets-for-api-docs/assets/dart-ui/blend_mode_xor.png)
  xor,

  /// Sum the components of the source and destination images.
  ///
  /// Transparency in a pixel of one of the images reduces the contribution of
  /// that image to the corresponding output pixel, as if the color of that
  /// pixel in that image was darker.
  ///
  /// This corresponds to the "Source plus Destination" Porter-Duff operator.
  ///
  /// This is the right blend mode for cross-fading between two images. Consider
  /// two images A and B, and an interpolation time variable _t_ (from 0.0 to
  /// 1.0). To cross fade between them, A should be drawn with opacity 1.0 - _t_
  /// into a new layer using [BlendMode.srcOver], and B should be drawn on top
  /// of it, at opacity _t_, into the same layer, using [BlendMode.plus].
  ///
  /// ![](https://flutter.github.io/assets-for-api-docs/assets/dart-ui/blend_mode_plus.png)
  plus,

  /// Multiply the color components of the source and destination images.
  ///
  /// This can only result in the same or darker colors (multiplying by white,
  /// 1.0, results in no change; multiplying by black, 0.0, results in black).
  ///
  /// When compositing two opaque images, this has similar effect to overlapping
  /// two transparencies on a projector.
  ///
  /// For a variant that also multiplies the alpha channel, consider [multiply].
  ///
  /// ![](https://flutter.github.io/assets-for-api-docs/assets/dart-ui/blend_mode_modulate.png)
  ///
  /// See also:
  ///
  ///  * [screen], which does a similar computation but inverted.
  ///  * [overlay], which combines [modulate] and [screen] to favor the
  ///    destination image.
  ///  * [hardLight], which combines [modulate] and [screen] to favor the
  ///    source image.
  modulate,

  // Following blend modes are defined in the CSS Compositing standard.

  /// Multiply the inverse of the components of the source and destination
  /// images, and inverse the result.
  ///
  /// Inverting the components means that a fully saturated channel (opaque
  /// white) is treated as the value 0.0, and values normally treated as 0.0
  /// (black, transparent) are treated as 1.0.
  ///
  /// This is essentially the same as [modulate] blend mode, but with the values
  /// of the colors inverted before the multiplication and the result being
  /// inverted back before rendering.
  ///
  /// This can only result in the same or lighter colors (multiplying by black,
  /// 1.0, results in no change; multiplying by white, 0.0, results in white).
  /// Similarly, in the alpha channel, it can only result in more opaque colors.
  ///
  /// This has similar effect to two projectors displaying their images on the
  /// same screen simultaneously.
  ///
  /// ![](https://flutter.github.io/assets-for-api-docs/assets/dart-ui/blend_mode_screen.png)
  ///
  /// See also:
  ///
  ///  * [modulate], which does a similar computation but without inverting the
  ///    values.
  ///  * [overlay], which combines [modulate] and [screen] to favor the
  ///    destination image.
  ///  * [hardLight], which combines [modulate] and [screen] to favor the
  ///    source image.
  screen, // The last coeff mode.
  /// Multiply the components of the source and destination images after
  /// adjusting them to favor the destination.
  ///
  /// Specifically, if the destination value is smaller, this multiplies it with
  /// the source value, whereas is the source value is smaller, it multiplies
  /// the inverse of the source value with the inverse of the destination value,
  /// then inverts the result.
  ///
  /// Inverting the components means that a fully saturated channel (opaque
  /// white) is treated as the value 0.0, and values normally treated as 0.0
  /// (black, transparent) are treated as 1.0.
  ///
  /// ![](https://flutter.github.io/assets-for-api-docs/assets/dart-ui/blend_mode_overlay.png)
  ///
  /// See also:
  ///
  ///  * [modulate], which always multiplies the values.
  ///  * [screen], which always multiplies the inverses of the values.
  ///  * [hardLight], which is similar to [overlay] but favors the source image
  ///    instead of the destination image.
  overlay,

  /// Composite the source and destination image by choosing the lowest value
  /// from each color channel.
  ///
  /// The opacity of the output image is computed in the same way as for
  /// [srcOver].
  ///
  /// ![](https://flutter.github.io/assets-for-api-docs/assets/dart-ui/blend_mode_darken.png)
  darken,

  /// Composite the source and destination image by choosing the highest value
  /// from each color channel.
  ///
  /// The opacity of the output image is computed in the same way as for
  /// [srcOver].
  ///
  /// ![](https://flutter.github.io/assets-for-api-docs/assets/dart-ui/blend_mode_lighten.png)
  lighten,

  /// Divide the destination by the inverse of the source.
  ///
  /// Inverting the components means that a fully saturated channel (opaque
  /// white) is treated as the value 0.0, and values normally treated as 0.0
  /// (black, transparent) are treated as 1.0.
  ///
  /// ![](https://flutter.github.io/assets-for-api-docs/assets/dart-ui/blend_mode_colorDodge.png)
  colorDodge,

  /// Divide the inverse of the destination by the source, and inverse the result.
  ///
  /// Inverting the components means that a fully saturated channel (opaque
  /// white) is treated as the value 0.0, and values normally treated as 0.0
  /// (black, transparent) are treated as 1.0.
  ///
  /// ![](https://flutter.github.io/assets-for-api-docs/assets/dart-ui/blend_mode_colorBurn.png)
  colorBurn,

  /// Multiply the components of the source and destination images after
  /// adjusting them to favor the source.
  ///
  /// Specifically, if the source value is smaller, this multiplies it with the
  /// destination value, whereas is the destination value is smaller, it
  /// multiplies the inverse of the destination value with the inverse of the
  /// source value, then inverts the result.
  ///
  /// Inverting the components means that a fully saturated channel (opaque
  /// white) is treated as the value 0.0, and values normally treated as 0.0
  /// (black, transparent) are treated as 1.0.
  ///
  /// ![](https://flutter.github.io/assets-for-api-docs/assets/dart-ui/blend_mode_hardLight.png)
  ///
  /// See also:
  ///
  ///  * [modulate], which always multiplies the values.
  ///  * [screen], which always multiplies the inverses of the values.
  ///  * [overlay], which is similar to [hardLight] but favors the destination
  ///    image instead of the source image.
  hardLight,

  /// Use [colorDodge] for source values below 0.5 and [colorBurn] for source
  /// values above 0.5.
  ///
  /// This results in a similar but softer effect than [overlay].
  ///
  /// ![](https://flutter.github.io/assets-for-api-docs/assets/dart-ui/blend_mode_softLight.png)
  ///
  /// See also:
  ///
  ///  * [color], which is a more subtle tinting effect.
  softLight,

  /// Subtract the smaller value from the bigger value for each channel.
  ///
  /// Compositing black has no effect; compositing white inverts the colors of
  /// the other image.
  ///
  /// The opacity of the output image is computed in the same way as for
  /// [srcOver].
  ///
  /// The effect is similar to [exclusion] but harsher.
  ///
  /// ![](https://flutter.github.io/assets-for-api-docs/assets/dart-ui/blend_mode_difference.png)
  difference,

  /// Subtract double the product of the two images from the sum of the two
  /// images.
  ///
  /// Compositing black has no effect; compositing white inverts the colors of
  /// the other image.
  ///
  /// The opacity of the output image is computed in the same way as for
  /// [srcOver].
  ///
  /// The effect is similar to [difference] but softer.
  ///
  /// ![](https://flutter.github.io/assets-for-api-docs/assets/dart-ui/blend_mode_exclusion.png)
  exclusion,

  /// Multiply the components of the source and destination images, including
  /// the alpha channel.
  ///
  /// This can only result in the same or darker colors (multiplying by white,
  /// 1.0, results in no change; multiplying by black, 0.0, results in black).
  ///
  /// Since the alpha channel is also multiplied, a fully-transparent pixel
  /// (opacity 0.0) in one image results in a fully transparent pixel in the
  /// output. This is similar to [dstIn], but with the colors combined.
  ///
  /// For a variant that multiplies the colors but does not multiply the alpha
  /// channel, consider [modulate].
  ///
  /// ![](https://flutter.github.io/assets-for-api-docs/assets/dart-ui/blend_mode_multiply.png)
  multiply, // The last separable mode.
  /// Take the hue of the source image, and the saturation and luminosity of the
  /// destination image.
  ///
  /// The effect is to tint the destination image with the source image.
  ///
  /// The opacity of the output image is computed in the same way as for
  /// [srcOver]. Regions that are entirely transparent in the source image take
  /// their hue from the destination.
  ///
  /// ![](https://flutter.github.io/assets-for-api-docs/assets/dart-ui/blend_mode_hue.png)
  ///
  /// See also:
  ///
  ///  * [color], which is a similar but stronger effect as it also applies the
  ///    saturation of the source image.
  ///  * [HSVColor], which allows colors to be expressed using Hue rather than
  ///    the red/green/blue channels of [Color].
  hue,

  /// Take the saturation of the source image, and the hue and luminosity of the
  /// destination image.
  ///
  /// The opacity of the output image is computed in the same way as for
  /// [srcOver]. Regions that are entirely transparent in the source image take
  /// their saturation from the destination.
  ///
  /// ![](https://flutter.github.io/assets-for-api-docs/assets/dart-ui/blend_mode_saturation.png)
  ///
  /// See also:
  ///
  ///  * [color], which also applies the hue of the source image.
  ///  * [luminosity], which applies the luminosity of the source image to the
  ///    destination.
  saturation,

  /// Take the hue and saturation of the source image, and the luminosity of the
  /// destination image.
  ///
  /// The effect is to tint the destination image with the source image.
  ///
  /// The opacity of the output image is computed in the same way as for
  /// [srcOver]. Regions that are entirely transparent in the source image take
  /// their hue and saturation from the destination.
  ///
  /// ![](https://flutter.github.io/assets-for-api-docs/assets/dart-ui/blend_mode_color.png)
  ///
  /// See also:
  ///
  ///  * [hue], which is a similar but weaker effect.
  ///  * [softLight], which is a similar tinting effect but also tints white.
  ///  * [saturation], which only applies the saturation of the source image.
  color,

  /// Take the luminosity of the source image, and the hue and saturation of the
  /// destination image.
  ///
  /// The opacity of the output image is computed in the same way as for
  /// [srcOver]. Regions that are entirely transparent in the source image take
  /// their luminosity from the destination.
  ///
  /// ![](https://flutter.github.io/assets-for-api-docs/assets/dart-ui/blend_mode_luminosity.png)
  ///
  /// See also:
  ///
  ///  * [saturation], which applies the saturation of the source image to the
  ///    destination.
  ///  * [ImageFilter.blur], which can be used with [BackdropFilter] for a
  ///    related effect.
  luminosity,
}

/// Quality levels for image sampling in [ImageFilter] and [Shader] objects that sample
/// images and for [Canvas] operations that render images.
///
/// When scaling up typically the quality is lowest at [none], higher at [low] and [medium],
/// and for very large scale factors (over 10x) the highest at [high].
///
/// When scaling down, [medium] provides the best quality especially when scaling an
/// image to less than half its size or for animating the scale factor between such
/// reductions. Otherwise, [low] and [high] provide similar effects for reductions of
/// between 50% and 100% but the image may lose detail and have dropouts below 50%.
///
/// To get high quality when scaling images up and down, or when the scale is
/// unknown, [medium] is typically a good balanced choice.
///
/// ![](https://flutter.github.io/assets-for-api-docs/assets/dart-ui/filter_quality.png)
///
/// See also:
///
///  * [Paint.filterQuality], which is used to pass [FilterQuality] to the
///    engine while using drawImage calls on a [Canvas].
///  * [ImageShader].
///  * [FragmentShader.setImageSampler].
///  * [ImageFilter.matrix].
///  * [Canvas.drawImage].
///  * [Canvas.drawImageRect].
///  * [Canvas.drawImageNine].
///  * [Canvas.drawAtlas].
enum FilterQuality {
  // This list and the values (order) should be kept in sync with the equivalent list
  // in lib/ui/painting/image_filter.cc

  /// The fastest filtering method, albeit also the lowest quality.
  ///
  /// This value results in a "Nearest Neighbor" algorithm which just
  /// repeats or eliminates pixels as an image is scaled up or down.
  none,

  /// Better quality than [none], faster than [medium].
  ///
  /// This value results in a "Bilinear" algorithm which smoothly
  /// interpolates between pixels in an image.
  low,

  /// The best all around filtering method that is only worse than [high]
  /// at extremely large scale factors.
  ///
  /// This value improves upon the "Bilinear" algorithm specified by [low]
  /// by utilizing a Mipmap that pre-computes high quality lower resolutions
  /// of the image at half (and quarter and eighth, etc.) sizes and then
  /// blends between those to prevent loss of detail at small scale sizes.
  ///
  /// {@template dart.ui.filterQuality.seeAlso}
  /// See also:
  ///
  ///  * [FilterQuality] class-level documentation that goes into detail about
  ///    relative qualities of the constant values.
  /// {@endtemplate}
  medium,

  /// Best possible quality when scaling up images by scale factors larger than
  /// 5-10x.
  ///
  /// When images are scaled down, this can be worse than [medium] for scales
  /// smaller than 0.5x, or when animating the scale factor.
  ///
  /// This option is also the slowest.
  ///
  /// This value results in a standard "Bicubic" algorithm which uses a 3rd order
  /// equation to smooth the abrupt transitions between pixels while preserving
  /// some of the sense of an edge and avoiding sharp peaks in the result.
  ///
  /// {@macro dart.ui.filterQuality.seeAlso}
  high,
}

/// Styles to use for line endings.
///
/// See also:
///
///  * [Paint.strokeCap] for how this value is used.
///  * [StrokeJoin] for the different kinds of line segment joins.
// These enum values must be kept in sync with DlStrokeCap.
enum StrokeCap {
  /// Begin and end contours with a flat edge and no extension.
  ///
  /// ![A butt cap ends line segments with a square end that stops at the end of
  /// the line segment.](https://flutter.github.io/assets-for-api-docs/assets/dart-ui/butt_cap.png)
  ///
  /// Compare to the [square] cap, which has the same shape, but extends past
  /// the end of the line by half a stroke width.
  butt,

  /// Begin and end contours with a semi-circle extension.
  ///
  /// ![A round cap adds a rounded end to the line segment that protrudes
  /// by one half of the thickness of the line (which is the radius of the cap)
  /// past the end of the segment.](https://flutter.github.io/assets-for-api-docs/assets/dart-ui/round_cap.png)
  ///
  /// The cap is colored in the diagram above to highlight it: in normal use it
  /// is the same color as the line.
  round,

  /// Begin and end contours with a half square extension. This is
  /// similar to extending each contour by half the stroke width (as
  /// given by [Paint.strokeWidth]).
  ///
  /// ![A square cap has a square end that effectively extends the line length
  /// by half of the stroke width.](https://flutter.github.io/assets-for-api-docs/assets/dart-ui/square_cap.png)
  ///
  /// The cap is colored in the diagram above to highlight it: in normal use it
  /// is the same color as the line.
  ///
  /// Compare to the [butt] cap, which has the same shape, but doesn't extend
  /// past the end of the line.
  square,
}

/// Styles to use for line segment joins.
///
/// This only affects line joins for polygons drawn by [Canvas.drawPath] and
/// rectangles, not points drawn as lines with [Canvas.drawPoints].
///
/// See also:
///
/// * [Paint.strokeJoin] and [Paint.strokeMiterLimit] for how this value is
///   used.
/// * [StrokeCap] for the different kinds of line endings.
// These enum values must be kept in sync with DlStrokeJoin.
enum StrokeJoin {
  /// Joins between line segments form sharp corners.
  ///
  /// {@animation 300 300 https://flutter.github.io/assets-for-api-docs/assets/dart-ui/miter_4_join.mp4}
  ///
  /// The center of the line segment is colored in the diagram above to
  /// highlight the join, but in normal usage the join is the same color as the
  /// line.
  ///
  /// See also:
  ///
  ///   * [Paint.strokeJoin], used to set the line segment join style to this
  ///     value.
  ///   * [Paint.strokeMiterLimit], used to define when a miter is drawn instead
  ///     of a bevel when the join is set to this value.
  miter,

  /// Joins between line segments are semi-circular.
  ///
  /// {@animation 300 300 https://flutter.github.io/assets-for-api-docs/assets/dart-ui/round_join.mp4}
  ///
  /// The center of the line segment is colored in the diagram above to
  /// highlight the join, but in normal usage the join is the same color as the
  /// line.
  ///
  /// See also:
  ///
  ///   * [Paint.strokeJoin], used to set the line segment join style to this
  ///     value.
  round,

  /// Joins between line segments connect the corners of the butt ends of the
  /// line segments to give a beveled appearance.
  ///
  /// {@animation 300 300 https://flutter.github.io/assets-for-api-docs/assets/dart-ui/bevel_join.mp4}
  ///
  /// The center of the line segment is colored in the diagram above to
  /// highlight the join, but in normal usage the join is the same color as the
  /// line.
  ///
  /// See also:
  ///
  ///   * [Paint.strokeJoin], used to set the line segment join style to this
  ///     value.
  bevel,
}

/// Strategies for painting shapes and paths on a canvas.
///
/// See [Paint.style].
// These enum values must be kept in sync with DlDrawStyle.
enum PaintingStyle {
  // This list comes from dl_paint.h and the values (order) should be kept
  // in sync.

  /// Apply the [Paint] to the inside of the shape. For example, when
  /// applied to the [Canvas.drawCircle] call, this results in a disc
  /// of the given size being painted.
  fill,

  /// Apply the [Paint] to the edge of the shape. For example, when
  /// applied to the [Canvas.drawCircle] call, this results is a hoop
  /// of the given size being painted. The line drawn on the edge will
  /// be the width given by the [Paint.strokeWidth] property.
  stroke,
}

/// Different ways to clip content.
///
/// See also:
///
///  * [Paint.isAntiAlias], the anti-aliasing switch for general draw operations.
enum Clip {
  /// No clip at all.
  ///
  /// This is the default option for most widgets: if the content does not
  /// overflow the widget boundary, don't pay any performance cost for clipping.
  ///
  /// If the content does overflow, consider the following [Clip] options:
  ///
  ///  * [hardEdge], which is the fastest clipping, but with lower fidelity.
  ///  * [antiAlias], which is a little slower than [hardEdge], but with smoothed edges.
  ///  * [antiAliasWithSaveLayer], which is much slower than [antiAlias], and should
  ///    rarely be used.
  none,

  /// Clip, but do not apply anti-aliasing.
  ///
  /// This mode enables clipping, but curves and non-axis-aligned straight lines will be
  /// jagged as no effort is made to anti-alias.
  ///
  /// Faster than other clipping modes, but slower than [none].
  ///
  /// This is a reasonable choice when clipping is needed, if the container is an axis-
  /// aligned rectangle or an axis-aligned rounded rectangle with very small corner radii.
  ///
  /// See also:
  ///
  ///  * [antiAlias], recommended when clipping is needed and the shape is not
  ///    an axis-aligned rectangle.
  hardEdge,

  /// Clip with anti-aliasing.
  ///
  /// This mode has anti-aliased clipping edges, which reduces jagged edges when
  /// the clip shape itself has edges that are diagonal, curved, or otherwise
  /// not axis-aligned.
  ///
  /// This is much faster than [antiAliasWithSaveLayer], but slower than [hardEdge].
  ///
  /// Unlike [hardEdge] and [antiAliasWithSaveLayer], this clipping can have
  /// bleeding edge artifacts
  /// ([Skia Fiddle example](https://fiddle.skia.org/c/21cb4c2b2515996b537f36e7819288ae)).
  ///
  /// See also:
  ///
  ///  * [hardEdge], which is faster, but with lower fidelity.
  ///  * [antiAliasWithSaveLayer], which is much slower, but avoids bleeding
  ///    edge artifacts.
  ///  * [Paint.isAntiAlias], which is the anti-aliasing switch for general draw operations.
  antiAlias,

  /// Clip with anti-aliasing and `saveLayer` immediately following the clip.
  ///
  /// This mode not only clips with anti-aliasing, but also allocates an offscreen
  /// buffer. All subsequent paints are carried out on that buffer before finally
  /// being clipped and composited back.
  ///
  /// This is very slow. It has no bleeding edge artifacts, unlike [antiAlias],
  /// but it changes the semantics as it introduces an offscreen buffer.
  /// For example, see this
  /// [Skia Fiddle without `saveLayer`](https://fiddle.skia.org/c/83ed46ceadaf90f36a4df3b98cbe1c35)
  /// and this
  /// [Skia Fiddle with `saveLayer`](https://fiddle.skia.org/c/704acfa049a7e99fbe685232c45d1582).
  ///
  /// Use this mode only if necessary. For example, if you have an
  /// image overlaid on a very different background color. In these
  /// cases, consider if you can avoid overlaying multiple colors in one
  /// location (e.g. by having the background color only present where the image is
  /// absent). If possible, prefer [antiAlias] as it is much faster.
  ///
  /// See also:
  ///
  ///  * [antiAlias], which is much faster, and has similar clipping results.
  ///  * [Canvas.saveLayer].
  antiAliasWithSaveLayer,
}

/// A description of the style to use when drawing on a [Canvas].
///
/// Most APIs on [Canvas] take a [Paint] object to describe the style
/// to use for that operation.
final class Paint {
  /// Constructs an empty [Paint] object with all fields initialized to
  /// their defaults.
  Paint();

  /// Constructs a new [Paint] object with the same fields as [other].
  ///
  /// Any changes made to the object returned will not affect [other], and
  /// changes to [other] will not affect the object returned.
  ///
  /// Backends (for example web versus native) may have different performance
  /// characteristics. If the code is performance-sensitive, consider profiling
  /// and falling back to reusing a single [Paint] object if necessary.
  Paint.from(Paint other) {
    // Every field on Paint is deeply immutable, so to create a copy of a Paint
    // object, we copy the underlying data buffer and the list of objects (which
    // are also deeply immutable).
    _data.buffer.asUint32List().setAll(0, other._data.buffer.asUint32List());
    _objects = other._objects?.toList();
  }

  // Paint objects are encoded in two buffers:
  //
  // * _data is binary data in four-byte fields, each of which is either a
  //   uint32_t or a float. The default value for each field is encoded as
  //   zero to make initialization trivial. Most values already have a default
  //   value of zero, but some, such as color, have a non-zero default value.
  //   To encode or decode these values, XOR the value with the default value.
  //
  // * _objects is a list of unencodable objects, typically wrappers for native
  //   objects. The objects are simply stored in the list without any additional
  //   encoding.
  //
  // The binary format must match the deserialization code in paint.cc.

  // C++ unit tests access this.
  @pragma('vm:entry-point')
  final ByteData _data = ByteData(_kDataByteCount);

  // Must match //lib/ui/painting/paint.cc.
  static const int _kIsAntiAliasIndex = 0;
  static const int _kColorRedIndex = 1;
  static const int _kColorGreenIndex = 2;
  static const int _kColorBlueIndex = 3;
  static const int _kColorAlphaIndex = 4;
  static const int _kColorSpaceIndex = 5;
  static const int _kBlendModeIndex = 6;
  static const int _kStyleIndex = 7;
  static const int _kStrokeWidthIndex = 8;
  static const int _kStrokeCapIndex = 9;
  static const int _kStrokeJoinIndex = 10;
  static const int _kStrokeMiterLimitIndex = 11;
  static const int _kFilterQualityIndex = 12;
  static const int _kMaskFilterIndex = 13;
  static const int _kMaskFilterBlurStyleIndex = 14;
  static const int _kMaskFilterSigmaIndex = 15;
  static const int _kInvertColorIndex = 16;

  static const int _kIsAntiAliasOffset = _kIsAntiAliasIndex << 2;
  static const int _kColorRedOffset = _kColorRedIndex << 2;
  static const int _kColorGreenOffset = _kColorGreenIndex << 2;
  static const int _kColorBlueOffset = _kColorBlueIndex << 2;
  static const int _kColorAlphaOffset = _kColorAlphaIndex << 2;
  static const int _kColorSpaceOffset = _kColorSpaceIndex << 2;
  static const int _kBlendModeOffset = _kBlendModeIndex << 2;
  static const int _kStyleOffset = _kStyleIndex << 2;
  static const int _kStrokeWidthOffset = _kStrokeWidthIndex << 2;
  static const int _kStrokeCapOffset = _kStrokeCapIndex << 2;
  static const int _kStrokeJoinOffset = _kStrokeJoinIndex << 2;
  static const int _kStrokeMiterLimitOffset = _kStrokeMiterLimitIndex << 2;
  static const int _kFilterQualityOffset = _kFilterQualityIndex << 2;
  static const int _kMaskFilterOffset = _kMaskFilterIndex << 2;
  static const int _kMaskFilterBlurStyleOffset = _kMaskFilterBlurStyleIndex << 2;
  static const int _kMaskFilterSigmaOffset = _kMaskFilterSigmaIndex << 2;
  static const int _kInvertColorOffset = _kInvertColorIndex << 2;

  // If you add more fields, remember to update _kDataByteCount.
  static const int _kDataByteCount = 68; // 4 * (last index + 1).

  // Binary format must match the deserialization code in paint.cc.
  // C++ unit tests access this.
  @pragma('vm:entry-point')
  List<Object?>? _objects;

  List<Object?> _ensureObjectsInitialized() {
    return _objects ??= List<Object?>.filled(_kObjectCount, null);
  }

  static const int _kShaderIndex = 0;
  static const int _kColorFilterIndex = 1;
  static const int _kImageFilterIndex = 2;
  static const int _kObjectCount = 3; // Must be one larger than the largest index.

  /// Whether to apply anti-aliasing to lines and images drawn on the
  /// canvas.
  ///
  /// Defaults to true.
  bool get isAntiAlias {
    return _data.getInt32(_kIsAntiAliasOffset, _kFakeHostEndian) == 0;
  }

  set isAntiAlias(bool value) {
    // We encode true as zero and false as one because the default value, which
    // we always encode as zero, is true.
    final encoded = value ? 0 : 1;
    _data.setInt32(_kIsAntiAliasOffset, encoded, _kFakeHostEndian);
  }

  // Must be kept in sync with the default in paint.cc.
  static const int _kColorDefault = 0xFF000000;

  /// The color to use when stroking or filling a shape.
  ///
  /// Defaults to opaque black.
  ///
  /// See also:
  ///
  ///  * [style], which controls whether to stroke or fill (or both).
  ///  * [colorFilter], which overrides [color].
  ///  * [shader], which overrides [color] with more elaborate effects.
  ///
  /// This color is not used when compositing. To colorize a layer, use
  /// [colorFilter].
  Color get color {
    final double red = _data.getFloat32(_kColorRedOffset, _kFakeHostEndian);
    final double green = _data.getFloat32(_kColorGreenOffset, _kFakeHostEndian);
    final double blue = _data.getFloat32(_kColorBlueOffset, _kFakeHostEndian);
    final double alpha = 1.0 - _data.getFloat32(_kColorAlphaOffset, _kFakeHostEndian);
    final ColorSpace colorSpace = _indexToColorSpace(
      _data.getInt32(_kColorSpaceOffset, _kFakeHostEndian),
    );
    return Color.from(alpha: alpha, red: red, green: green, blue: blue, colorSpace: colorSpace);
  }

  set color(Color value) {
    _data.setFloat32(_kColorRedOffset, value.r, _kFakeHostEndian);
    _data.setFloat32(_kColorGreenOffset, value.g, _kFakeHostEndian);
    _data.setFloat32(_kColorBlueOffset, value.b, _kFakeHostEndian);
    _data.setFloat32(_kColorAlphaOffset, 1.0 - value.a, _kFakeHostEndian);
    _data.setInt32(_kColorSpaceOffset, _colorSpaceToIndex(value.colorSpace), _kFakeHostEndian);
  }

  // Must be kept in sync with the default in paint.cc.
  static final int _kBlendModeDefault = BlendMode.srcOver.index;

  /// A blend mode to apply when a shape is drawn or a layer is composited.
  ///
  /// The source colors are from the shape being drawn (e.g. from
  /// [Canvas.drawPath]) or layer being composited (the graphics that were drawn
  /// between the [Canvas.saveLayer] and [Canvas.restore] calls), after applying
  /// the [colorFilter], if any.
  ///
  /// The destination colors are from the background onto which the shape or
  /// layer is being composited.
  ///
  /// Defaults to [BlendMode.srcOver].
  ///
  /// See also:
  ///
  ///  * [Canvas.saveLayer], which uses its [Paint]'s [blendMode] to composite
  ///    the layer when [Canvas.restore] is called.
  ///  * [BlendMode], which discusses the user of [Canvas.saveLayer] with
  ///    [blendMode].
  BlendMode get blendMode {
    final int encoded = _data.getInt32(_kBlendModeOffset, _kFakeHostEndian);
    return BlendMode.values[encoded ^ _kBlendModeDefault];
  }

  set blendMode(BlendMode value) {
    final int encoded = value.index ^ _kBlendModeDefault;
    _data.setInt32(_kBlendModeOffset, encoded, _kFakeHostEndian);
  }

  /// Whether to paint inside shapes, the edges of shapes, or both.
  ///
  /// Defaults to [PaintingStyle.fill].
  PaintingStyle get style {
    return PaintingStyle.values[_data.getInt32(_kStyleOffset, _kFakeHostEndian)];
  }

  set style(PaintingStyle value) {
    final int encoded = value.index;
    _data.setInt32(_kStyleOffset, encoded, _kFakeHostEndian);
  }

  /// How wide to make edges drawn when [style] is set to
  /// [PaintingStyle.stroke]. The width is given in logical pixels measured in
  /// the direction orthogonal to the direction of the path.
  ///
  /// Defaults to 0.0, which correspond to a hairline width.
  double get strokeWidth {
    return _data.getFloat32(_kStrokeWidthOffset, _kFakeHostEndian);
  }

  set strokeWidth(double value) {
    final encoded = value;
    _data.setFloat32(_kStrokeWidthOffset, encoded, _kFakeHostEndian);
  }

  /// The kind of finish to place on the end of lines drawn when
  /// [style] is set to [PaintingStyle.stroke].
  ///
  /// Defaults to [StrokeCap.butt], i.e. no caps.
  StrokeCap get strokeCap {
    return StrokeCap.values[_data.getInt32(_kStrokeCapOffset, _kFakeHostEndian)];
  }

  set strokeCap(StrokeCap value) {
    final int encoded = value.index;
    _data.setInt32(_kStrokeCapOffset, encoded, _kFakeHostEndian);
  }

  /// The kind of finish to place on the joins between segments.
  ///
  /// This applies to paths drawn when [style] is set to [PaintingStyle.stroke],
  /// It does not apply to points drawn as lines with [Canvas.drawPoints].
  ///
  /// Defaults to [StrokeJoin.miter], i.e. sharp corners.
  ///
  /// Some examples of joins:
  ///
  /// {@animation 300 300 https://flutter.github.io/assets-for-api-docs/assets/dart-ui/miter_4_join.mp4}
  ///
  /// {@animation 300 300 https://flutter.github.io/assets-for-api-docs/assets/dart-ui/round_join.mp4}
  ///
  /// {@animation 300 300 https://flutter.github.io/assets-for-api-docs/assets/dart-ui/bevel_join.mp4}
  ///
  /// The centers of the line segments are colored in the diagrams above to
  /// highlight the joins, but in normal usage the join is the same color as the
  /// line.
  ///
  /// See also:
  ///
  ///  * [strokeMiterLimit] to control when miters are replaced by bevels when
  ///    this is set to [StrokeJoin.miter].
  ///  * [strokeCap] to control what is drawn at the ends of the stroke.
  ///  * [StrokeJoin] for the definitive list of stroke joins.
  StrokeJoin get strokeJoin {
    return StrokeJoin.values[_data.getInt32(_kStrokeJoinOffset, _kFakeHostEndian)];
  }

  set strokeJoin(StrokeJoin value) {
    final int encoded = value.index;
    _data.setInt32(_kStrokeJoinOffset, encoded, _kFakeHostEndian);
  }

  // Must be kept in sync with the default in paint.cc.
  static const double _kStrokeMiterLimitDefault = 4.0;

  /// The limit for miters to be drawn on segments when the join is set to
  /// [StrokeJoin.miter] and the [style] is set to [PaintingStyle.stroke]. If
  /// this limit is exceeded, then a [StrokeJoin.bevel] join will be drawn
  /// instead. This may cause some 'popping' of the corners of a path if the
  /// angle between line segments is animated, as seen in the diagrams below.
  ///
  /// This limit is expressed as a limit on the length of the miter.
  ///
  /// Defaults to 4.0.  Using zero as a limit will cause a [StrokeJoin.bevel]
  /// join to be used all the time.
  ///
  /// {@animation 300 300 https://flutter.github.io/assets-for-api-docs/assets/dart-ui/miter_0_join.mp4}
  ///
  /// {@animation 300 300 https://flutter.github.io/assets-for-api-docs/assets/dart-ui/miter_4_join.mp4}
  ///
  /// {@animation 300 300 https://flutter.github.io/assets-for-api-docs/assets/dart-ui/miter_6_join.mp4}
  ///
  /// The centers of the line segments are colored in the diagrams above to
  /// highlight the joins, but in normal usage the join is the same color as the
  /// line.
  ///
  /// See also:
  ///
  ///  * [strokeJoin] to control the kind of finish to place on the joins
  ///    between segments.
  ///  * [strokeCap] to control what is drawn at the ends of the stroke.
  double get strokeMiterLimit {
    return _data.getFloat32(_kStrokeMiterLimitOffset, _kFakeHostEndian);
  }

  set strokeMiterLimit(double value) {
    final double encoded = value - _kStrokeMiterLimitDefault;
    _data.setFloat32(_kStrokeMiterLimitOffset, encoded, _kFakeHostEndian);
  }

  /// A mask filter (for example, a blur) to apply to a shape after it has been
  /// drawn but before it has been composited into the image.
  ///
  /// See [MaskFilter] for details.
  MaskFilter? get maskFilter {
    switch (_data.getInt32(_kMaskFilterOffset, _kFakeHostEndian)) {
      case MaskFilter._TypeNone:
        return null;
      case MaskFilter._TypeBlur:
        return MaskFilter.blur(
          BlurStyle.values[_data.getInt32(_kMaskFilterBlurStyleOffset, _kFakeHostEndian)],
          _data.getFloat32(_kMaskFilterSigmaOffset, _kFakeHostEndian),
        );
    }
    return null;
  }

  set maskFilter(MaskFilter? value) {
    if (value == null) {
      _data.setInt32(_kMaskFilterOffset, MaskFilter._TypeNone, _kFakeHostEndian);
      _data.setInt32(_kMaskFilterBlurStyleOffset, 0, _kFakeHostEndian);
      _data.setFloat32(_kMaskFilterSigmaOffset, 0.0, _kFakeHostEndian);
    } else {
      // For now we only support one kind of MaskFilter, so we don't need to
      // check what the type is if it's not null.
      _data.setInt32(_kMaskFilterOffset, MaskFilter._TypeBlur, _kFakeHostEndian);
      _data.setInt32(_kMaskFilterBlurStyleOffset, value._style.index, _kFakeHostEndian);
      _data.setFloat32(_kMaskFilterSigmaOffset, value._sigma, _kFakeHostEndian);
    }
  }

  /// Controls the performance vs quality trade-off to use when sampling bitmaps,
  /// as with an [ImageShader], or when drawing images, as with [Canvas.drawImage],
  /// [Canvas.drawImageRect], [Canvas.drawImageNine] or [Canvas.drawAtlas].
  ///
  /// Defaults to [FilterQuality.none].
  // TODO(ianh): verify that the image drawing methods actually respect this
  FilterQuality get filterQuality {
    return FilterQuality.values[_data.getInt32(_kFilterQualityOffset, _kFakeHostEndian)];
  }

  set filterQuality(FilterQuality value) {
    final int encoded = value.index;
    _data.setInt32(_kFilterQualityOffset, encoded, _kFakeHostEndian);
  }

  /// The shader to use when stroking or filling a shape.
  ///
  /// When this is null, the [color] is used instead.
  ///
  /// See also:
  ///
  ///  * [Gradient], a shader that paints a color gradient.
  ///  * [ImageShader], a shader that tiles an [Image].
  ///  * [colorFilter], which overrides [shader].
  ///  * [color], which is used if [shader] and [colorFilter] are null.
  Shader? get shader {
    return _objects?[_kShaderIndex] as Shader?;
  }

  set shader(Shader? value) {
    assert(() {
      assert(value == null || !value.debugDisposed, 'Attempted to set a disposed shader to $this');
      return true;
    }());
    assert(() {
      if (value is FragmentShader) {
        if (!value._validateSamplers()) {
          throw Exception('Invalid FragmentShader ${value._debugName ?? ''}: missing sampler');
        }
      }
      return true;
    }());
    _ensureObjectsInitialized()[_kShaderIndex] = value;
  }

  /// A color filter to apply when a shape is drawn or when a layer is
  /// composited.
  ///
  /// See [ColorFilter] for details.
  ///
  /// When a shape is being drawn, [colorFilter] overrides [color] and [shader].
  ColorFilter? get colorFilter {
    final nativeFilter = _objects?[_kColorFilterIndex] as _ColorFilter?;
    return nativeFilter?.creator;
  }

  set colorFilter(ColorFilter? value) {
    final _ColorFilter? nativeFilter = value?._toNativeColorFilter();
    if (nativeFilter == null) {
      if (_objects != null) {
        _objects![_kColorFilterIndex] = null;
      }
    } else {
      _ensureObjectsInitialized()[_kColorFilterIndex] = nativeFilter;
    }
  }

  /// The [ImageFilter] to use when drawing raster images.
  ///
  /// For example, to blur an image using [Canvas.drawImage], apply an
  /// [ImageFilter.blur]:
  ///
  /// ```dart
  /// void paint(Canvas canvas, Size size) {
  ///   canvas.drawImage(
  ///     _image,
  ///     ui.Offset.zero,
  ///     Paint()..imageFilter = ui.ImageFilter.blur(sigmaX: 0.5, sigmaY: 0.5),
  ///   );
  /// }
  /// ```
  ///
  /// See also:
  ///
  ///  * [MaskFilter], which is used for drawing geometry.
  ImageFilter? get imageFilter {
    final nativeFilter = _objects?[_kImageFilterIndex] as _ImageFilter?;
    return nativeFilter?.creator;
  }

  set imageFilter(ImageFilter? value) {
    if (value == null) {
      if (_objects != null) {
        _objects![_kImageFilterIndex] = null;
      }
    } else {
      final List<Object?> objects = _ensureObjectsInitialized();
      final imageFilter = objects[_kImageFilterIndex] as _ImageFilter?;
      if (imageFilter?.creator != value) {
        objects[_kImageFilterIndex] = value._toNativeImageFilter();
      }
    }
  }

  /// Whether the colors of the image are inverted when drawn.
  ///
  /// Inverting the colors of an image applies a new color filter that will
  /// be composed with any user provided color filters. This is primarily
  /// used for implementing smart invert on iOS.
  bool get invertColors {
    return _data.getInt32(_kInvertColorOffset, _kFakeHostEndian) == 1;
  }

  set invertColors(bool value) {
    _data.setInt32(_kInvertColorOffset, value ? 1 : 0, _kFakeHostEndian);
  }

  @override
  String toString() {
    if (const bool.fromEnvironment('dart.vm.product')) {
      return super.toString();
    }
    final result = StringBuffer();
    var semicolon = '';
    result.write('Paint(');
    if (style == PaintingStyle.stroke) {
      result.write('$style');
      if (strokeWidth != 0.0) {
        result.write(' ${strokeWidth.toStringAsFixed(1)}');
      } else {
        result.write(' hairline');
      }
      if (strokeCap != StrokeCap.butt) {
        result.write(' $strokeCap');
      }
      if (strokeJoin == StrokeJoin.miter) {
        if (strokeMiterLimit != _kStrokeMiterLimitDefault) {
          result.write(' $strokeJoin up to ${strokeMiterLimit.toStringAsFixed(1)}');
        }
      } else {
        result.write(' $strokeJoin');
      }
      semicolon = '; ';
    }
    if (!isAntiAlias) {
      result.write('${semicolon}antialias off');
      semicolon = '; ';
    }
    if (color != const Color(_kColorDefault)) {
      result.write('$semicolon$color');
      semicolon = '; ';
    }
    if (blendMode.index != _kBlendModeDefault) {
      result.write('$semicolon$blendMode');
      semicolon = '; ';
    }
    if (colorFilter != null) {
      result.write('${semicolon}colorFilter: $colorFilter');
      semicolon = '; ';
    }
    if (maskFilter != null) {
      result.write('${semicolon}maskFilter: $maskFilter');
      semicolon = '; ';
    }
    if (filterQuality != FilterQuality.none) {
      result.write('${semicolon}filterQuality: $filterQuality');
      semicolon = '; ';
    }
    if (shader != null) {
      result.write('${semicolon}shader: $shader');
      semicolon = '; ';
    }
    if (imageFilter != null) {
      result.write('${semicolon}imageFilter: $imageFilter');
      semicolon = '; ';
    }
    if (invertColors) {
      result.write('${semicolon}invert: $invertColors');
    }
    result.write(')');
    return result.toString();
  }
}

/// The color space describes the colors that are available to an [Image].
///
/// This value can help decide which [ImageByteFormat] to use with
/// [Image.toByteData]. Images that are in the [extendedSRGB] color space
/// should use something like [ImageByteFormat.rawExtendedRgba128] so that
/// colors outside of the sRGB gamut aren't lost.
///
/// This is also the result of [Image.colorSpace].
///
/// See also: https://en.wikipedia.org/wiki/Color_space
enum ColorSpace {
  /// The sRGB color space.
  ///
  /// You may know this as the standard color space for the web or the color
  /// space of non-wide-gamut Flutter apps.
  ///
  /// See also: https://en.wikipedia.org/wiki/SRGB
  sRGB,

  /// A color space that is backwards compatible with sRGB but can represent
  /// colors outside of that gamut with values outside of [0..1]. In order to
  /// see the extended values an [ImageByteFormat] like
  /// [ImageByteFormat.rawExtendedRgba128] must be used.
  extendedSRGB,

  /// The Display P3 color space.
  ///
  /// This is a wide gamut color space that has broad hardware support. It's
  /// supported in cases like using Impeller on iOS. When used on a platform
  /// that doesn't support Display P3, the colors will be clamped to sRGB.
  ///
  /// See also: https://en.wikipedia.org/wiki/DCI-P3
  displayP3,
}

int _colorSpaceToIndex(ColorSpace colorSpace) {
  switch (colorSpace) {
    case ColorSpace.sRGB:
      return 0;
    case ColorSpace.extendedSRGB:
      return 1;
    case ColorSpace.displayP3:
      return 2;
  }
}

ColorSpace _indexToColorSpace(int index) {
  switch (index) {
    case 0:
      return ColorSpace.sRGB;
    case 1:
      return ColorSpace.extendedSRGB;
    case 2:
      return ColorSpace.displayP3;
    default:
      throw ArgumentError('Unknown color space: $index');
  }
}

/// The format in which image bytes should be returned when using
/// [Image.toByteData].
// We do not expect to add more encoding formats to the ImageByteFormat enum,
// considering the binary size of the engine after LTO optimization. You can
// use the third-party pure dart image library to encode other formats.
// See: https://github.com/flutter/flutter/issues/16635 for more details.
enum ImageByteFormat {
  /// Raw RGBA format.
  ///
  /// Unencoded bytes, in RGBA row-primary form with premultiplied alpha, 8 bits per channel.
  rawRgba,

  /// Raw straight RGBA format.
  ///
  /// Unencoded bytes, in RGBA row-primary form with straight alpha, 8 bits per channel.
  rawStraightRgba,

  /// Raw unmodified format.
  ///
  /// Unencoded bytes, in the image's existing format. For example, a grayscale
  /// image may use a single 8-bit channel for each pixel.
  rawUnmodified,

  /// Raw extended range RGBA format.
  ///
  /// Unencoded bytes, in RGBA row-primary form with straight alpha, 32 bit
  /// float (IEEE 754 binary32) per channel.
  ///
  /// Example usage:
  ///
  /// ```dart
  /// import 'dart:ui' as ui;
  /// import 'dart:typed_data';
  ///
  /// Future<Map<String, double>> getFirstPixel(ui.Image image) async {
  ///   final ByteData data =
  ///       (await image.toByteData(format: ui.ImageByteFormat.rawExtendedRgba128))!;
  ///   final Float32List floats = Float32List.view(data.buffer);
  ///   return <String, double>{
  ///     'r': floats[0],
  ///     'g': floats[1],
  ///     'b': floats[2],
  ///     'a': floats[3],
  ///   };
  /// }
  /// ```
  rawExtendedRgba128,

  /// PNG format.
  ///
  /// A loss-less compression format for images. This format is well suited for
  /// images with hard edges, such as screenshots or sprites, and images with
  /// text. Transparency is supported. The PNG format supports images up to
  /// 2,147,483,647 pixels in either dimension, though in practice available
  /// memory provides a more immediate limitation on maximum image size.
  ///
  /// PNG images normally use the `.png` file extension and the `image/png` MIME
  /// type.
  ///
  /// See also:
  ///
  ///  * <https://en.wikipedia.org/wiki/Portable_Network_Graphics>, the Wikipedia page on PNG.
  ///  * <https://tools.ietf.org/rfc/rfc2083.txt>, the PNG standard.
  png,
}

/// The format of pixel data given to [decodeImageFromPixels].
enum PixelFormat {
  /// Each pixel is 32 bits, with the highest 8 bits encoding red, the next 8
  /// bits encoding green, the next 8 bits encoding blue, and the lowest 8 bits
  /// encoding alpha. Premultiplied alpha is used.
  rgba8888,

  /// Each pixel is 32 bits, with the highest 8 bits encoding blue, the next 8
  /// bits encoding green, the next 8 bits encoding red, and the lowest 8 bits
  /// encoding alpha. Premultiplied alpha is used.
  bgra8888,

  /// Each pixel is 128 bits, where each color component is a 32 bit float that
  /// is normalized across the sRGB gamut.  The first float is the red
  /// component, followed by: green, blue and alpha. Premultiplied alpha isn't
  /// used, matching [ImageByteFormat.rawExtendedRgba128].
  rgbaFloat32,

  /// Each pixel is 32 bits, the red channel is just one 32 bit float.
  rFloat32,
}

/// The format of pixel data of the texture generated by
/// [decodeImageFromPixels].
enum TargetPixelFormat {
  /// Unspecified pixel format, let the engine decide the best pixel format.
  dontCare,

  /// Each pixel is 128 bits, where each color component is a 32 bit float.
  rgbaFloat32,

  /// Each pixel is 32 bits, the red channel is just one 32 bit float.
  rFloat32,
}

/// Signature for [Image] lifecycle events.
typedef ImageEventCallback = void Function(Image image);

/// Opaque handle to raw decoded image data (pixels).
///
/// To obtain an [Image] object, use the [ImageDescriptor] API.
///
/// To draw an [Image], use one of the methods on the [Canvas] class, such as
/// [Canvas.drawImage].
///
/// A class or method that receives an image object must call [dispose] on the
/// handle when it is no longer needed. To create a shareable reference to the
/// underlying image, call [clone]. The method or object that receives
/// the new instance will then be responsible for disposing it, and the
/// underlying image itself will be disposed when all outstanding handles are
/// disposed.
///
/// If `dart:ui` passes an `Image` object and the recipient wishes to share
/// that handle with other callers, [clone] must be called _before_ [dispose].
/// A handle that has been disposed cannot create new handles anymore.
///
/// See also:
///
///  * [Image](https://api.flutter.dev/flutter/widgets/Image-class.html), the class in the [widgets] library.
///  * [ImageDescriptor], which allows reading information about the image and
///    creating a codec to decode it.
///  * [instantiateImageCodec], a utility method that wraps [ImageDescriptor].
class Image {
  Image._(this._image, this.width, this.height) {
    assert(() {
      _debugStack = StackTrace.current;
      return true;
    }());
    _image._handles.add(this);
    onCreate?.call(this);
  }

  // C++ unit tests access this.
  @pragma('vm:entry-point')
  final _Image _image;

  /// A callback that is invoked to report an image creation.
  ///
  /// It's preferred to use [MemoryAllocations] in flutter/foundation.dart
  /// than to use [onCreate] directly because [MemoryAllocations]
  /// allows multiple callbacks.
  static ImageEventCallback? onCreate;

  /// A callback that is invoked to report the image disposal.
  ///
  /// It's preferred to use [MemoryAllocations] in flutter/foundation.dart
  /// than to use [onDispose] directly because [MemoryAllocations]
  /// allows multiple callbacks.
  static ImageEventCallback? onDispose;

  StackTrace? _debugStack;

  /// The number of image pixels along the image's horizontal axis.
  final int width;

  /// The number of image pixels along the image's vertical axis.
  final int height;

  bool _disposed = false;

  /// Release this handle's claim on the underlying Image. This handle is no
  /// longer usable after this method is called.
  ///
  /// Once all outstanding handles have been disposed, the underlying image will
  /// be disposed as well.
  ///
  /// In debug mode, [debugGetOpenHandleStackTraces] will return a list of
  /// [StackTrace] objects from all open handles' creation points. This is
  /// useful when trying to determine what parts of the program are keeping an
  /// image resident in memory.
  void dispose() {
    onDispose?.call(this);
    assert(!_disposed && !_image._disposed);
    assert(_image._handles.contains(this));
    _disposed = true;
    final bool removed = _image._handles.remove(this);
    assert(removed);
    if (_image._handles.isEmpty) {
      _image.dispose();
    }
  }

  /// Whether this reference to the underlying image is [dispose]d.
  ///
  /// This only returns a valid value if asserts are enabled, and must not be
  /// used otherwise.
  bool get debugDisposed {
    bool? disposed;
    assert(() {
      disposed = _disposed;
      return true;
    }());
    return disposed ??
        (throw StateError('Image.debugDisposed is only available when asserts are enabled.'));
  }

  /// Converts the [Image] object into a byte array.
  ///
  /// The [format] argument specifies the format in which the bytes will be
  /// returned.
  ///
  /// Using [ImageByteFormat.rawRgba] on an image in the color space
  /// [ColorSpace.extendedSRGB] will result in the gamut being squished to fit
  /// into the sRGB gamut, resulting in the loss of wide-gamut colors.
  ///
  /// Returns a future that completes with the binary image data or an error
  /// if encoding fails.
  // We do not expect to add more encoding formats to the ImageByteFormat enum,
  // considering the binary size of the engine after LTO optimization. You can
  // use the third-party pure dart image library to encode other formats.
  // See: https://github.com/flutter/flutter/issues/16635 for more details.
  Future<ByteData?> toByteData({ImageByteFormat format = ImageByteFormat.rawRgba}) {
    assert(!_disposed && !_image._disposed);
    return _image.toByteData(format: format);
  }

  /// The color space that is used by the [Image]'s colors.
  ///
  /// This value is a consequence of how the [Image] has been created.  For
  /// example, loading a PNG that is in the Display P3 color space will result
  /// in a [ColorSpace.extendedSRGB] image.
  ///
  /// On rendering backends that don't support wide gamut colors (anything but
  /// iOS impeller), wide gamut images will still report [ColorSpace.sRGB] if
  /// rendering wide gamut colors isn't supported.
  // Note: The docstring will become outdated as new platforms support wide
  // gamut color, please keep it up to date.
  ColorSpace get colorSpace {
    final int colorSpaceValue = _image.colorSpace;
    switch (colorSpaceValue) {
      case 0:
        return ColorSpace.sRGB;
      case 1:
        return ColorSpace.extendedSRGB;
      default:
        throw UnsupportedError('Unrecognized color space: $colorSpaceValue');
    }
  }

  /// If asserts are enabled, returns the [StackTrace]s of each open handle from
  /// [clone], in creation order.
  ///
  /// If asserts are disabled, this method always returns null.
  List<StackTrace>? debugGetOpenHandleStackTraces() {
    List<StackTrace>? stacks;
    assert(() {
      stacks = _image._handles.map((Image handle) => handle._debugStack!).toList();
      return true;
    }());
    return stacks;
  }

  /// Creates a disposable handle to this image.
  ///
  /// Holders of an [Image] must dispose of the image when they no longer need
  /// to access it or draw it. However, once the underlying image is disposed,
  /// it is no longer possible to use it. If a holder of an image needs to share
  /// access to that image with another object or method, [clone] creates a
  /// duplicate handle. The underlying image will only be disposed once all
  /// outstanding handles are disposed. This allows for safe sharing of image
  /// references while still disposing of the underlying resources when all
  /// consumers are finished.
  ///
  /// It is safe to pass an [Image] handle to another object or method if the
  /// current holder no longer needs it.
  ///
  /// To check whether two [Image] references are referring to the same
  /// underlying image memory, use [isCloneOf] rather than the equality operator
  /// or [identical].
  ///
  /// The following example demonstrates valid usage.
  ///
  /// ```dart
  /// import 'dart:async';
  /// import 'dart:typed_data';
  /// import 'dart:ui';
  ///
  /// Future<Image> _loadImage(int width, int height) {
  ///   final Completer<Image> completer = Completer<Image>();
  ///   decodeImageFromPixels(
  ///     Uint8List.fromList(List<int>.filled(width * height * 4, 0xFF)),
  ///     width,
  ///     height,
  ///     PixelFormat.rgba8888,
  ///     // Don't worry about disposing or cloning this image - responsibility
  ///     // is transferred to the caller, and that is safe since this method
  ///     // will not touch it again.
  ///     (Image image) => completer.complete(image),
  ///   );
  ///   return completer.future;
  /// }
  ///
  /// Future<void> main() async {
  ///   final Image image = await _loadImage(5, 5);
  ///   // Make sure to clone the image, because MyHolder might dispose it
  ///   // and we need to access it again.
  ///   final MyImageHolder holder = MyImageHolder(image.clone());
  ///   final MyImageHolder holder2 = MyImageHolder(image.clone());
  ///   // Now we dispose it because we won't need it again.
  ///   image.dispose();
  ///
  ///   final PictureRecorder recorder = PictureRecorder();
  ///   final Canvas canvas = Canvas(recorder);
  ///
  ///   holder.draw(canvas);
  ///   holder.dispose();
  ///
  ///   canvas.translate(50, 50);
  ///   holder2.draw(canvas);
  ///   holder2.dispose();
  /// }
  ///
  /// class MyImageHolder {
  ///   MyImageHolder(this.image);
  ///
  ///   final Image image;
  ///
  ///   void draw(Canvas canvas) {
  ///     canvas.drawImage(image, Offset.zero, Paint());
  ///   }
  ///
  ///   void dispose() => image.dispose();
  /// }
  /// ```
  ///
  /// The returned object behaves identically to this image. Calling
  /// [dispose] on it will only dispose the underlying native resources if it
  /// is the last remaining handle.
  Image clone() {
    if (_disposed) {
      throw StateError(
        'Cannot clone a disposed image.\n'
        'The clone() method of a previously-disposed Image was called. Once an '
        'Image object has been disposed, it can no longer be used to create '
        'handles, as the underlying data may have been released.',
      );
    }
    assert(!_image._disposed);
    return Image._(_image, width, height);
  }

  /// Returns true if `other` is a [clone] of this and thus shares the same
  /// underlying image memory, even if this or `other` is [dispose]d.
  ///
  /// This method may return false for two images that were decoded from the
  /// same underlying asset, if they are not sharing the same memory. For
  /// example, if the same file is decoded using [instantiateImageCodec] twice,
  /// or the same bytes are decoded using [decodeImageFromPixels] twice, there
  /// will be two distinct [Image]s that render the same but do not share
  /// underlying memory, and so will not be treated as clones of each other.
  bool isCloneOf(Image other) => other._image == _image;

  @override
  String toString() => _image.toString();
}

@pragma('vm:entry-point')
base class _Image extends NativeFieldWrapperClass1 {
  // This class is created by the engine, and should not be instantiated
  // or extended directly.
  //
  // _Images are always handed out wrapped in [Image]s. To create an [Image],
  // use the ImageDescriptor API.
  @pragma('vm:entry-point')
  _Image._();

  @Native<Int32 Function(Pointer<Void>)>(symbol: 'Image::width', isLeaf: true)
  external int get width;

  @Native<Int32 Function(Pointer<Void>)>(symbol: 'Image::height', isLeaf: true)
  external int get height;

  Future<ByteData?> toByteData({ImageByteFormat format = ImageByteFormat.rawRgba}) {
    return _futurizeWithError((_CallbackWithError<ByteData?> callback) {
      return _toByteData(format.index, (Uint8List? encoded, String? error) {
        if (error == null && encoded != null) {
          callback(encoded.buffer.asByteData(), null);
        } else {
          callback(null, error);
        }
      });
    });
  }

  /// Returns an error message on failure, null on success.
  @Native<Handle Function(Pointer<Void>, Int32, Handle)>(symbol: 'Image::toByteData')
  external String? _toByteData(int format, void Function(Uint8List?, String?) callback);

  bool _disposed = false;
  void dispose() {
    assert(!_disposed);
    assert(
      _handles.isEmpty,
      'Attempted to dispose of an Image object that has ${_handles.length} '
      'open handles.\n'
      'If you see this, it is a bug in dart:ui. Please file an issue at '
      'https://github.com/flutter/flutter/issues/new.',
    );
    _disposed = true;
    _dispose();
  }

  /// This can't be a leaf call because the native function calls Dart API
  /// (Dart_SetNativeInstanceField).
  @Native<Void Function(Pointer<Void>)>(symbol: 'Image::dispose')
  external void _dispose();

  final Set<Image> _handles = <Image>{};

  @Native<Int32 Function(Pointer<Void>)>(symbol: 'Image::colorSpace')
  external int get colorSpace;

  @override
  String toString() => '[$width\u00D7$height]';
}

@pragma('vm:entry-point')
Image _wrapImage(_Image image) {
  return Image._(image, image.width, image.height);
}

/// Callback signature for [decodeImageFromList].
typedef ImageDecoderCallback = void Function(Image result);

/// Information for a single frame of an animation.
///
/// To obtain an instance of the [FrameInfo] interface, see
/// [Codec.getNextFrame].
///
/// The recipient of an instance of this class is responsible for calling
/// [Image.dispose] on [image]. To share the image with other interested
/// parties, use [Image.clone]. If the [FrameInfo] object itself is passed to
/// another method or object, that method or object must assume it is
/// responsible for disposing the image when done, and the passer must not
/// access the [image] after that point.
///
/// For example, the following code sample is incorrect:
///
/// ```dart
/// /// BAD
/// Future<void> nextFrameRoutine(ui.Codec codec) async {
///   final ui.FrameInfo frameInfo = await codec.getNextFrame();
///   _cacheImage(frameInfo);
///   // ERROR - _cacheImage is now responsible for disposing the image, and
///   // the image may not be available any more for this drawing routine.
///   _drawImage(frameInfo);
///   // ERROR again - the previous methods might or might not have created
///   // handles to the image.
///   frameInfo.image.dispose();
/// }
/// ```
///
/// Correct usage is:
///
/// ```dart
/// /// GOOD
/// Future<void> nextFrameRoutine(ui.Codec codec) async {
///   final ui.FrameInfo frameInfo = await codec.getNextFrame();
///   _cacheImage(frameInfo.image.clone(), frameInfo.duration);
///   _drawImage(frameInfo.image.clone(), frameInfo.duration);
///   // This method is done with its handle, and has passed handles to its
///   // clients already.
///   // The image will live until those clients dispose of their handles, and
///   // this one must not be disposed since it will not be used again.
///   frameInfo.image.dispose();
/// }
/// ```
class FrameInfo {
  /// This class is created by the engine, and should not be instantiated
  /// or extended directly.
  ///
  /// To obtain an instance of the [FrameInfo] interface, see
  /// [Codec.getNextFrame].
  FrameInfo._({required this.duration, required this.image});

  /// The duration this frame should be shown.
  ///
  /// A zero duration indicates that the frame should be shown indefinitely.
  final Duration duration;

  /// The [Image] object for this frame.
  ///
  /// This object must be disposed by the recipient of this frame info.
  ///
  /// To share this image with other interested parties, use [Image.clone].
  final Image image;
}

/// A handle to an image codec.
///
/// This class is created by the engine, and should not be instantiated
/// or extended directly.
///
/// To obtain an instance of the [Codec] interface, see
/// [instantiateImageCodec].
abstract class Codec {
  /// Number of frames in this image.
  int get frameCount;

  /// Number of times to repeat the animation.
  ///
  /// * 0 when the animation should be played once.
  /// * -1 for infinity repetitions.
  int get repetitionCount;

  /// Fetches the next animation frame.
  ///
  /// Wraps back to the first frame after returning the last frame.
  ///
  /// The returned future can complete with an error if the decoding has failed.
  ///
  /// The caller of this method is responsible for disposing the
  /// [FrameInfo.image] on the returned object.
  Future<FrameInfo> getNextFrame();

  /// Release the resources used by this object. The object is no longer usable
  /// after this method is called.
  ///
  /// This can't be a leaf call because the native function calls Dart API
  /// (Dart_SetNativeInstanceField).
  void dispose();
}

base class _NativeCodec extends NativeFieldWrapperClass1 implements Codec {
  //
  // This class is created by the engine, and should not be instantiated
  // or extended directly.
  //
  // To obtain an instance of the [Codec] interface, see
  // [instantiateImageCodec].
  _NativeCodec._();

  int? _cachedFrameCount;

  @override
  int get frameCount => _cachedFrameCount ??= _frameCount;

  @Native<Int32 Function(Pointer<Void>)>(symbol: 'Codec::frameCount', isLeaf: true)
  external int get _frameCount;

  int? _cachedRepetitionCount;

  @override
  int get repetitionCount => _cachedRepetitionCount ??= _repetitionCount;

  @Native<Int32 Function(Pointer<Void>)>(symbol: 'Codec::repetitionCount', isLeaf: true)
  external int get _repetitionCount;

  @override
  Future<FrameInfo> getNextFrame() async {
    final completer = Completer<FrameInfo>.sync();
    final String? error = _getNextFrame((
      _Image? image,
      int durationMilliseconds,
      String decodeError,
    ) {
      if (image == null) {
        if (decodeError.isEmpty) {
          decodeError = 'Codec failed to produce an image, possibly due to invalid image data.';
        }
        completer.completeError(Exception(decodeError));
      } else {
        completer.complete(
          FrameInfo._(
            image: Image._(image, image.width, image.height),
            duration: Duration(milliseconds: durationMilliseconds),
          ),
        );
      }
    });
    if (error != null) {
      throw Exception(error);
    }
    return completer.future;
  }

  /// Returns an error message on failure, null on success.
  @Native<Handle Function(Pointer<Void>, Handle)>(symbol: 'Codec::getNextFrame')
  external String? _getNextFrame(void Function(_Image?, int, String) callback);

  @override
  @Native<Void Function(Pointer<Void>)>(symbol: 'Codec::dispose')
  external void dispose();

  @override
  String toString() => 'Codec(${_cachedFrameCount == null ? "" : "$_cachedFrameCount frames"})';
}

/// Instantiates an image [Codec].
///
/// This method is a convenience wrapper around the [ImageDescriptor] API, and
/// using [ImageDescriptor] directly is preferred since it allows the caller to
/// make better determinations about how and whether to use the `targetWidth`
/// and `targetHeight` parameters.
///
/// The `list` parameter is the binary image data (e.g a PNG or GIF binary data).
/// The data can be for either static or animated images. The following image
/// formats are supported:
// Update this list when changing the list of supported codecs.
/// {@template dart.ui.imageFormats}
/// JPEG, PNG, GIF, Animated GIF, WebP, Animated WebP, BMP, and WBMP. Additional
/// formats may be supported by the underlying platform. Flutter will
/// attempt to call platform API to decode unrecognized formats, and if the
/// platform API supports decoding the image Flutter will be able to render it.
/// {@endtemplate}
///
/// The `targetWidth` and `targetHeight` arguments specify the size of the
/// output image, in image pixels. If they are not equal to the intrinsic
/// dimensions of the image, then the image will be scaled after being decoded.
/// If the `allowUpscaling` parameter is not set to true, both dimensions will
/// be capped at the intrinsic dimensions of the image, even if only one of
/// them would have exceeded those intrinsic dimensions. If exactly one of these
/// two arguments is specified, then the aspect ratio will be maintained while
/// forcing the image to match the other given dimension. If neither is
/// specified, then the image maintains its intrinsic size.
///
/// Scaling the image to larger than its intrinsic size should usually be
/// avoided, since it causes the image to use more memory than necessary.
/// Instead, prefer scaling the [Canvas] transform. If the image must be scaled
/// up, the `allowUpscaling` parameter must be set to true.
///
/// The returned future can complete with an error if the image decoding has
/// failed.
Future<Codec> instantiateImageCodec(
  Uint8List list, {
  int? targetWidth,
  int? targetHeight,
  bool allowUpscaling = true,
}) async {
  final ImmutableBuffer buffer = await ImmutableBuffer.fromUint8List(list);
  return instantiateImageCodecFromBuffer(
    buffer,
    targetWidth: targetWidth,
    targetHeight: targetHeight,
    allowUpscaling: allowUpscaling,
  );
}

/// Instantiates an image [Codec].
///
/// This method is a convenience wrapper around the [ImageDescriptor] API, and
/// using [ImageDescriptor] directly is preferred since it allows the caller to
/// make better determinations about how and whether to use the `targetWidth`
/// and `targetHeight` parameters.
///
/// The [buffer] parameter is the binary image data (e.g a PNG or GIF binary data).
/// The data can be for either static or animated images. The following image
/// formats are supported: {@macro dart.ui.imageFormats}
///
/// The [buffer] will be disposed by this method once the codec has been created,
/// so the caller must relinquish ownership of the [buffer] when they call this
/// method.
///
/// The [targetWidth] and [targetHeight] arguments specify the size of the
/// output image, in image pixels. If they are not equal to the intrinsic
/// dimensions of the image, then the image will be scaled after being decoded.
/// If the `allowUpscaling` parameter is not set to true, both dimensions will
/// be capped at the intrinsic dimensions of the image, even if only one of
/// them would have exceeded those intrinsic dimensions. If exactly one of these
/// two arguments is specified, then the aspect ratio will be maintained while
/// forcing the image to match the other given dimension. If neither is
/// specified, then the image maintains its intrinsic size.
///
/// Scaling the image to larger than its intrinsic size should usually be
/// avoided, since it causes the image to use more memory than necessary.
/// Instead, prefer scaling the [Canvas] transform. If the image must be scaled
/// up, the `allowUpscaling` parameter must be set to true.
///
/// The returned future can complete with an error if the image decoding has
/// failed.
Future<Codec> instantiateImageCodecFromBuffer(
  ImmutableBuffer buffer, {
  int? targetWidth,
  int? targetHeight,
  bool allowUpscaling = true,
}) {
  return instantiateImageCodecWithSize(
    buffer,
    getTargetSize: (int intrinsicWidth, int intrinsicHeight) {
      if (!allowUpscaling) {
        if (targetWidth != null && targetWidth! > intrinsicWidth) {
          targetWidth = intrinsicWidth;
        }
        if (targetHeight != null && targetHeight! > intrinsicHeight) {
          targetHeight = intrinsicHeight;
        }
      }
      return TargetImageSize(width: targetWidth, height: targetHeight);
    },
  );
}

/// Instantiates an image [Codec].
///
/// This method is a convenience wrapper around the [ImageDescriptor] API.
///
/// The [buffer] parameter is the binary image data (e.g a PNG or GIF binary
/// data). The data can be for either static or animated images. The following
/// image formats are supported: {@macro dart.ui.imageFormats}
///
/// The [buffer] will be disposed by this method once the codec has been
/// created, so the caller must relinquish ownership of the [buffer] when they
/// call this method.
///
/// The [getTargetSize] parameter, when specified, will be invoked and passed
/// the image's intrinsic size to determine the size to decode the image to.
/// The width and the height of the size it returns must be positive values
/// greater than or equal to 1, or null. It is valid to return a
/// [TargetImageSize] that specifies only one of `width` and `height` with the
/// other remaining null, in which case the omitted dimension will be scaled to
/// maintain the aspect ratio of the original dimensions. When both are null or
/// omitted, the image will be decoded at its native resolution (as will be the
/// case if the [getTargetSize] parameter is omitted).
///
/// Scaling the image to larger than its intrinsic size should usually be
/// avoided, since it causes the image to use more memory than necessary.
/// Instead, prefer scaling the [Canvas] transform.
///
/// The returned future can complete with an error if the image decoding has
/// failed.
Future<Codec> instantiateImageCodecWithSize(
  ImmutableBuffer buffer, {
  TargetImageSizeCallback? getTargetSize,
}) async {
  getTargetSize ??= _getDefaultImageSize;
  final ImageDescriptor descriptor = await ImageDescriptor.encoded(buffer);
  try {
    final TargetImageSize targetSize = getTargetSize(descriptor.width, descriptor.height);
    assert(targetSize.width == null || targetSize.width! > 0);
    assert(targetSize.height == null || targetSize.height! > 0);
    return await descriptor.instantiateCodec(
      targetWidth: targetSize.width,
      targetHeight: targetSize.height,
    );
  } finally {
    buffer.dispose();
  }
}

TargetImageSize _getDefaultImageSize(int intrinsicWidth, int intrinsicHeight) {
  return const TargetImageSize();
}

/// Signature for a callback that determines the size to which an image should
/// be decoded given its intrinsic size.
///
/// See also:
///
///  * [instantiateImageCodecWithSize], which used this signature for its
///    `getTargetSize` argument.
typedef TargetImageSizeCallback = TargetImageSize Function(int intrinsicWidth, int intrinsicHeight);

/// A specification of the size to which an image should be decoded.
///
/// See also:
///
///  * [TargetImageSizeCallback], a callback that returns instances of this
///    class when consulted by image decoding methods such as
///    [instantiateImageCodecWithSize].
class TargetImageSize {
  /// Creates a new instance of this class.
  ///
  /// The `width` and `height` may both be null, but if they're non-null, they
  /// must be positive.
  const TargetImageSize({this.width, this.height})
    : assert(width == null || width > 0),
      assert(height == null || height > 0);

  /// The width into which to load the image.
  ///
  /// If this is non-null, the image will be decoded into the specified width.
  /// If this is null and [height] is also null, the image will be decoded into
  /// its intrinsic size. If this is null and [height] is non-null, the image
  /// will be decoded into a width that maintains its intrinsic aspect ratio
  /// while respecting the [height] value.
  ///
  /// If this value is non-null, it must be positive.
  final int? width;

  /// The height into which to load the image.
  ///
  /// If this is non-null, the image will be decoded into the specified height.
  /// If this is null and [width] is also null, the image will be decoded into
  /// its intrinsic size. If this is null and [width] is non-null, the image
  /// will be decoded into a height that maintains its intrinsic aspect ratio
  /// while respecting the [width] value.
  ///
  /// If this value is non-null, it must be positive.
  final int? height;

  @override
  String toString() => 'TargetImageSize($width x $height)';
}

/// Loads a single image frame from a byte array into an [Image] object.
///
/// This is a convenience wrapper around [instantiateImageCodec]. Prefer using
/// [instantiateImageCodec] which also supports multi frame images and offers
/// better error handling. This function swallows asynchronous errors.
void decodeImageFromList(Uint8List list, ImageDecoderCallback callback) {
  _decodeImageFromListAsync(list, callback);
}

Future<void> _decodeImageFromListAsync(Uint8List list, ImageDecoderCallback callback) async {
  final Codec codec = await instantiateImageCodec(list);
  final FrameInfo frameInfo;
  try {
    frameInfo = await codec.getNextFrame();
  } finally {
    codec.dispose();
  }
  callback(frameInfo.image);
}

/// Convert an array of pixel values into an [Image] object.
///
/// The `pixels` parameter is the pixel data. They are packed in bytes in the
/// order described by `format`, then grouped in rows, from left to right,
/// then top to bottom.
///
/// The `rowBytes` parameter is the number of bytes consumed by each row of
/// pixels in the data buffer. If unspecified, it defaults to `width` multiplied
/// by the number of bytes per pixel in the provided `format`.
///
/// The `targetWidth` and `targetHeight` arguments specify the size of the
/// output image, in image pixels. If they are not equal to the intrinsic
/// dimensions of the image, then the image will be scaled after being decoded.
/// If the `allowUpscaling` parameter is not set to true, both dimensions will
/// be capped at the intrinsic dimensions of the image, even if only one of
/// them would have exceeded those intrinsic dimensions. If exactly one of these
/// two arguments is specified, then the aspect ratio will be maintained while
/// forcing the image to match the other given dimension. If neither is
/// specified, then the image maintains its intrinsic size.
///
/// Scaling the image to larger than its intrinsic size should usually be
/// avoided, since it causes the image to use more memory than necessary.
/// Instead, prefer scaling the [Canvas] transform. If the image must be scaled
/// up, the `allowUpscaling` parameter must be set to true.
void decodeImageFromPixels(
  Uint8List pixels,
  int width,
  int height,
  PixelFormat format,
  ImageDecoderCallback callback, {
  int? rowBytes,
  int? targetWidth,
  int? targetHeight,
  bool allowUpscaling = true,
  TargetPixelFormat targetFormat = TargetPixelFormat.dontCare,
}) {
  if (targetWidth != null) {
    assert(allowUpscaling || targetWidth <= width);
  }
  if (targetHeight != null) {
    assert(allowUpscaling || targetHeight <= height);
  }

  ImmutableBuffer.fromUint8List(pixels).then((ImmutableBuffer buffer) {
    final descriptor = ImageDescriptor.raw(
      buffer,
      width: width,
      height: height,
      rowBytes: rowBytes,
      pixelFormat: format,
    );

    if (!allowUpscaling) {
      if (targetWidth != null && targetWidth! > descriptor.width) {
        targetWidth = descriptor.width;
      }
      if (targetHeight != null && targetHeight! > descriptor.height) {
        targetHeight = descriptor.height;
      }
    }

    descriptor
        .instantiateCodec(
          targetWidth: targetWidth,
          targetHeight: targetHeight,
          targetFormat: targetFormat,
        )
        .then((Codec codec) {
          final Future<FrameInfo> frameInfo = codec.getNextFrame();
          codec.dispose();
          return frameInfo;
        })
        .then((FrameInfo frameInfo) {
          buffer.dispose();
          descriptor.dispose();

          return callback(frameInfo.image);
        });
  });
}

/// Decodes the given [pixels] into an [Image] synchronously.
///
/// The [pixels] are expected to be in the format specified by [format].
///
/// The [width] and [height] arguments specify the dimensions of the image.
///
/// This function returns an [Image] immediately. The image might not be
/// fully decoded yet, but it can be drawn to a [Canvas].
Image decodeImageFromPixelsSync(Uint8List pixels, int width, int height, PixelFormat format) {
  final image = Image._(_Image._(), width, height);
  _decodeImageFromPixelsSync(pixels, width, height, format.index, image._image);
  return image;
}

@Native<Void Function(Handle, Int32, Int32, Int32, Handle)>(
  symbol: 'Image::decodeImageFromPixelsSync',
)
external void _decodeImageFromPixelsSync(
  Uint8List pixels,
  int width,
  int height,
  int format,
  _Image outImage,
);

/// Determines the winding rule that decides how the interior of a [Path] is
/// calculated.
///
/// This enum is used by the [Path.fillType] property.
enum PathFillType {
  /// The interior is defined by a non-zero sum of signed edge crossings.
  ///
  /// For a given point, the point is considered to be on the inside of the path
  /// if a line drawn from the point to infinity crosses lines going clockwise
  /// around the point a different number of times than it crosses lines going
  /// counter-clockwise around that point.
  ///
  /// See: <https://en.wikipedia.org/wiki/Nonzero-rule>
  nonZero,

  /// The interior is defined by an odd number of edge crossings.
  ///
  /// For a given point, the point is considered to be on the inside of the path
  /// if a line drawn from the point to infinity crosses an odd number of lines.
  ///
  /// See: <https://en.wikipedia.org/wiki/Even-odd_rule>
  evenOdd,
}

/// Strategies for combining paths.
///
/// See also:
///
/// * [Path.combine], which uses this enum to decide how to combine two paths.
// Must be kept in sync with SkPathOp
enum PathOperation {
  /// Subtract the second path from the first path.
  ///
  /// For example, if the two paths are overlapping circles of equal diameter
  /// but differing centers, the result would be a crescent portion of the
  /// first circle that was not overlapped by the second circle.
  ///
  /// See also:
  ///
  ///  * [reverseDifference], which is the same but subtracting the first path
  ///    from the second.
  difference,

  /// Create a new path that is the intersection of the two paths, leaving the
  /// overlapping pieces of the path.
  ///
  /// For example, if the two paths are overlapping circles of equal diameter
  /// but differing centers, the result would be only the overlapping portion
  /// of the two circles.
  ///
  /// See also:
  ///  * [xor], which is the inverse of this operation
  intersect,

  /// Create a new path that is the union (inclusive-or) of the two paths.
  ///
  /// For example, if the two paths are overlapping circles of equal diameter
  /// but differing centers, the result would be a figure-eight like shape
  /// matching the outer boundaries of both circles.
  union,

  /// Create a new path that is the exclusive-or of the two paths, leaving
  /// everything but the overlapping pieces of the path.
  ///
  /// For example, if the two paths are overlapping circles of equal diameter
  /// but differing centers, the figure-eight like shape less the overlapping parts
  ///
  /// See also:
  ///  * [intersect], which is the inverse of this operation
  xor,

  /// Subtract the first path from the second path.
  ///
  /// For example, if the two paths are overlapping circles of equal diameter
  /// but differing centers, the result would be a crescent portion of the
  /// second circle that was not overlapped by the first circle.
  ///
  /// See also:
  ///
  ///  * [difference], which is the same but subtracting the second path
  ///    from the first.
  reverseDifference,
}

/// A handle for the framework to hold and retain an engine layer across frames.
abstract class EngineLayer {
  /// Release the resources used by this object. The object is no longer usable
  /// after this method is called.
  ///
  /// EngineLayers indirectly retain platform specific graphics resources. Some
  /// of these resources, such as images, may be memory intensive. It is
  /// important to dispose of EngineLayer objects that will no longer be used as
  /// soon as possible to avoid retaining these resources until the next
  /// garbage collection.
  ///
  /// Once this EngineLayer is disposed, it is no longer eligible for use as a
  /// retained layer, and must not be passed as an `oldLayer` to any of the
  /// [SceneBuilder] methods which accept that parameter.
  ///
  /// This can't be a leaf call because the native function calls Dart API
  /// (Dart_SetNativeInstanceField).
  void dispose();
}

base class _NativeEngineLayer extends NativeFieldWrapperClass1 implements EngineLayer {
  /// This class is created by the engine, and should not be instantiated
  /// or extended directly.
  _NativeEngineLayer._();

  @override
  @Native<Void Function(Pointer<Void>)>(symbol: 'EngineLayer::dispose')
  external void dispose();
}

/// A complex, one-dimensional subset of a plane.
///
/// A path consists of a number of sub-paths, and a _current point_.
///
/// Sub-paths consist of segments of various types, such as lines,
/// arcs, or beziers. Sub-paths can be open or closed, and can
/// self-intersect.
///
/// Closed sub-paths enclose a (possibly discontiguous) region of the
/// plane based on the current [fillType].
///
/// The _current point_ is initially at the origin. After each
/// operation adding a segment to a sub-path, the current point is
/// updated to the end of that segment.
///
/// Paths can be drawn on canvases using [Canvas.drawPath], and can
/// used to create clip regions using [Canvas.clipPath].
abstract class Path {
  // TODO(matanlurey): have original authors document; see https://github.com/flutter/flutter/issues/151917.
  // ignore: public_member_api_docs
  factory Path() = _NativePath;

  /// Creates a copy of another [Path].
  ///
  /// This copy is fast and does not require additional memory unless either
  /// the `source` path or the path returned by this constructor are modified.
  factory Path.from(Path source) {
    final clonedPath = _NativePath._();
    (source as _NativePath)._clone(clonedPath);
    return clonedPath;
  }

  /// Determines how the interior of this path is calculated.
  ///
  /// Defaults to the non-zero winding rule, [PathFillType.nonZero].
  PathFillType get fillType;
  set fillType(PathFillType value);

  /// Starts a new sub-path at the given coordinate.
  void moveTo(double x, double y);

  /// Starts a new sub-path at the given offset from the current point.
  void relativeMoveTo(double dx, double dy);

  /// Adds a straight line segment from the current point to the given
  /// point.
  void lineTo(double x, double y);

  /// Adds a straight line segment from the current point to the point
  /// at the given offset from the current point.
  void relativeLineTo(double dx, double dy);

  /// Adds a quadratic bezier segment that curves from the current
  /// point to the given point (x2,y2), using the control point
  /// (x1,y1).
  ///
  /// ![](https://flutter.github.io/assets-for-api-docs/assets/dart-ui/path_quadratic_to.png#gh-light-mode-only)
  /// ![](https://flutter.github.io/assets-for-api-docs/assets/dart-ui/path_quadratic_to_dark.png#gh-dark-mode-only)
  void quadraticBezierTo(double x1, double y1, double x2, double y2);

  /// Adds a quadratic bezier segment that curves from the current
  /// point to the point at the offset (x2,y2) from the current point,
  /// using the control point at the offset (x1,y1) from the current
  /// point.
  void relativeQuadraticBezierTo(double x1, double y1, double x2, double y2);

  /// Adds a cubic bezier segment that curves from the current point
  /// to the given point (x3,y3), using the control points (x1,y1) and
  /// (x2,y2).
  ///
  /// ![](https://flutter.github.io/assets-for-api-docs/assets/dart-ui/path_cubic_to.png#gh-light-mode-only)
  /// ![](https://flutter.github.io/assets-for-api-docs/assets/dart-ui/path_cubic_to_dark.png#gh-dark-mode-only)
  void cubicTo(double x1, double y1, double x2, double y2, double x3, double y3);

  /// Adds a cubic bezier segment that curves from the current point
  /// to the point at the offset (x3,y3) from the current point, using
  /// the control points at the offsets (x1,y1) and (x2,y2) from the
  /// current point.
  void relativeCubicTo(double x1, double y1, double x2, double y2, double x3, double y3);

  /// Adds a bezier segment that curves from the current point to the
  /// given point (x2,y2), using the control points (x1,y1) and the
  /// weight w. If the weight is greater than 1, then the curve is a
  /// hyperbola; if the weight equals 1, it's a parabola; and if it is
  /// less than 1, it is an ellipse.
  ///
  /// ![](https://flutter.github.io/assets-for-api-docs/assets/dart-ui/path_conic_to.png#gh-light-mode-only)
  /// ![](https://flutter.github.io/assets-for-api-docs/assets/dart-ui/path_conic_to_dark.png#gh-dark-mode-only)
  void conicTo(double x1, double y1, double x2, double y2, double w);

  /// Adds a bezier segment that curves from the current point to the
  /// point at the offset (x2,y2) from the current point, using the
  /// control point at the offset (x1,y1) from the current point and
  /// the weight w. If the weight is greater than 1, then the curve is
  /// a hyperbola; if the weight equals 1, it's a parabola; and if it
  /// is less than 1, it is an ellipse.
  void relativeConicTo(double x1, double y1, double x2, double y2, double w);

  /// If the `forceMoveTo` argument is false, adds a straight line
  /// segment and an arc segment.
  ///
  /// If the `forceMoveTo` argument is true, starts a new sub-path
  /// consisting of an arc segment.
  ///
  /// In either case, the arc segment consists of the arc that follows
  /// the edge of the oval bounded by the given rectangle, from
  /// startAngle radians around the oval up to startAngle + sweepAngle
  /// radians around the oval, with zero radians being the point on
  /// the right hand side of the oval that crosses the horizontal line
  /// that intersects the center of the rectangle and with positive
  /// angles going clockwise around the oval.
  ///
  /// The line segment added if `forceMoveTo` is false starts at the
  /// current point and ends at the start of the arc. Note that this
  /// method does not draw anything if the [sweepAngle] is a multiple
  /// of $2\pi$ (e.g., $2\pi$, $4\pi$). If you need to draw a full
  /// circle or an overlapping arc, use [addArc] as a workaround.
  void arcTo(Rect rect, double startAngle, double sweepAngle, bool forceMoveTo);

  /// Appends up to four conic curves weighted to describe an oval of `radius`
  /// and rotated by `rotation` (measured in degrees and clockwise).
  ///
  /// The first curve begins from the last point in the path and the last ends
  /// at `arcEnd`. The curves follow a path in a direction determined by
  /// `clockwise` and `largeArc` in such a way that the sweep angle
  /// is always less than 360 degrees.
  ///
  /// A simple line is appended if either radii are zero or the last
  /// point in the path is `arcEnd`. The radii are scaled to fit the last path
  /// point if both are greater than zero but too small to describe an arc.
  ///
  void arcToPoint(
    Offset arcEnd, {
    Radius radius = Radius.zero,
    double rotation = 0.0,
    bool largeArc = false,
    bool clockwise = true,
  });

  /// Appends up to four conic curves weighted to describe an oval of `radius`
  /// and rotated by `rotation` (measured in degrees and clockwise).
  ///
  /// The last path point is described by (px, py).
  ///
  /// The first curve begins from the last point in the path and the last ends
  /// at `arcEndDelta.dx + px` and `arcEndDelta.dy + py`. The curves follow a
  /// path in a direction determined by `clockwise` and `largeArc`
  /// in such a way that the sweep angle is always less than 360 degrees.
  ///
  /// A simple line is appended if either radii are zero, or, both
  /// `arcEndDelta.dx` and `arcEndDelta.dy` are zero. The radii are scaled to
  /// fit the last path point if both are greater than zero but too small to
  /// describe an arc.
  void relativeArcToPoint(
    Offset arcEndDelta, {
    Radius radius = Radius.zero,
    double rotation = 0.0,
    bool largeArc = false,
    bool clockwise = true,
  });

  /// Adds a new sub-path that consists of four lines that outline the
  /// given rectangle.
  void addRect(Rect rect);

  /// Adds a new sub-path that consists of a curve that forms the
  /// ellipse that fills the given rectangle.
  ///
  /// To add a circle, pass an appropriate rectangle as `oval`. [Rect.fromCircle]
  /// can be used to easily describe the circle's center [Offset] and radius.
  void addOval(Rect oval);

  /// Adds a new sub-path with one arc segment that consists of the arc
  /// that follows the edge of the oval bounded by the given
  /// rectangle, from startAngle radians around the oval up to
  /// startAngle + sweepAngle radians around the oval, with zero
  /// radians being the point on the right hand side of the oval that
  /// crosses the horizontal line that intersects the center of the
  /// rectangle and with positive angles going clockwise around the
  /// oval.
  ///
  /// ![](https://flutter.github.io/assets-for-api-docs/assets/dart-ui/path_add_arc.png#gh-light-mode-only)
  /// ![](https://flutter.github.io/assets-for-api-docs/assets/dart-ui/path_add_arc_dark.png#gh-dark-mode-only)
  ///
  /// ![](https://flutter.github.io/assets-for-api-docs/assets/dart-ui/path_add_arc_ccw.png#gh-light-mode-only)
  /// ![](https://flutter.github.io/assets-for-api-docs/assets/dart-ui/path_add_arc_ccw_dark.png#gh-dark-mode-only)
  void addArc(Rect oval, double startAngle, double sweepAngle);

  /// Adds a new sub-path with a sequence of line segments that connect the given
  /// points.
  ///
  /// If `close` is true, a final line segment will be added that connects the
  /// last point to the first point.
  ///
  /// The `points` argument is interpreted as offsets from the origin.
  void addPolygon(List<Offset> points, bool close);

  /// Adds a new sub-path that consists of the straight lines and
  /// curves needed to form the rounded rectangle described by the
  /// argument.
  void addRRect(RRect rrect);

  /// Adds a new sub-path that consists of curves needed to form the rounded
  /// superellipse described by the argument.
  void addRSuperellipse(RSuperellipse rsuperellipse);

  /// Adds the sub-paths of `path`, offset by `offset`, to this path.
  ///
  /// If `matrix4` is specified, the path will be transformed by this matrix
  /// after the matrix is translated by the given offset. The matrix is a 4x4
  /// matrix stored in column major order.
  void addPath(Path path, Offset offset, {Float64List? matrix4});

  /// Adds the sub-paths of `path`, offset by `offset`, to this path.
  /// The current sub-path is extended with the first sub-path
  /// of `path`, connecting them with a lineTo if necessary.
  ///
  /// If `matrix4` is specified, the path will be transformed by this matrix
  /// after the matrix is translated by the given `offset`.  The matrix is a 4x4
  /// matrix stored in column major order.
  void extendWithPath(Path path, Offset offset, {Float64List? matrix4});

  /// Closes the last sub-path, as if a straight line had been drawn
  /// from the current point to the first point of the sub-path.
  void close();

  /// Clears the [Path] object of all sub-paths, returning it to the
  /// same state it had when it was created. The _current point_ is
  /// reset to the origin.
  void reset();

  /// Tests to see if the given point is within the path. (That is, whether the
  /// point would be in the visible portion of the path if the path was used
  /// with [Canvas.clipPath].)
  ///
  /// The `point` argument is interpreted as an offset from the origin.
  ///
  /// Returns true if the point is in the path, and false otherwise.
  bool contains(Offset point);

  /// Returns a copy of the path with all the segments of every
  /// sub-path translated by the given offset.
  Path shift(Offset offset);

  /// Returns a copy of the path with all the segments of every
  /// sub-path transformed by the given matrix.
  Path transform(Float64List matrix4);

  /// Computes the bounding rectangle for this path.
  ///
  /// A path containing only axis-aligned points on the same straight line will
  /// have no area, and therefore `Rect.isEmpty` will return true for such a
  /// path. Consider checking `rect.width + rect.height > 0.0` instead, or
  /// using the [computeMetrics] API to check the path length.
  ///
  /// For many more elaborate paths, the bounds may be inaccurate.  For example,
  /// when a path contains a circle, the points used to compute the bounds are
  /// the circle's implied control points, which form a square around the circle;
  /// if the circle has a transformation applied using [transform] then that
  /// square is rotated, and the (axis-aligned, non-rotated) bounding box
  /// therefore ends up grossly overestimating the actual area covered by the
  /// circle.
  // see https://skia.org/user/api/SkPath_Reference#SkPath_getBounds
  Rect getBounds();

  /// Combines the two paths according to the manner specified by the given
  /// `operation`.
  ///
  /// The resulting path will be constructed from non-overlapping contours. The
  /// curve order is reduced where possible so that cubics may be turned into
  /// quadratics, and quadratics maybe turned into lines.
  static Path combine(PathOperation operation, Path path1, Path path2) {
    final path = _NativePath();
    if (path._op(path1 as _NativePath, path2 as _NativePath, operation.index)) {
      return path;
    }
    throw StateError(
      'Path.combine() failed.  This may be due an invalid path; in particular, check for NaN values.',
    );
  }

  /// Creates a [PathMetrics] object for this path, which can describe various
  /// properties about the contours of the path.
  ///
  /// A [Path] is made up of zero or more contours. A contour is made up of
  /// connected curves and segments, created via methods like [lineTo],
  /// [cubicTo], [arcTo], [quadraticBezierTo], their relative counterparts, as
  /// well as the add* methods such as [addRect]. Creating a new [Path] starts
  /// a new contour once it has any drawing instructions, and another new
  /// contour is started for each [moveTo] instruction.
  ///
  /// A [PathMetric] object describes properties of an individual contour,
  /// such as its length, whether it is closed, what the tangent vector of a
  /// particular offset along the path is. It also provides a method for
  /// creating sub-paths: [PathMetric.extractPath].
  ///
  /// Calculating [PathMetric] objects is not trivial. The [PathMetrics] object
  /// returned by this method is a lazy [Iterable], meaning it only performs
  /// calculations when the iterator is moved to the next [PathMetric]. Callers
  /// that wish to memoize this iterable can easily do so by using
  /// [Iterable.toList] on the result of this method. In particular, callers
  /// looking for information about how many contours are in the path should
  /// either store the result of `path.computeMetrics().length`, or should use
  /// `path.computeMetrics().toList()` so they can repeatedly check the length,
  /// since calling `Iterable.length` causes traversal of the entire iterable.
  ///
  /// In particular, callers should be aware that [PathMetrics.length] is the
  /// number of contours, **not the length of the path**. To get the length of
  /// a contour in a path, use [PathMetric.length].
  ///
  /// Zero-length contours (where the start and end points are the same, such as
  /// `Path()..lineTo(0, 0)`) are not included in the returned [PathMetrics].
  /// Only contours with a positive length will have a corresponding [PathMetric].
  ///
  /// If `forceClosed` is set to true, the contours of the path will be measured
  /// as if they had been closed, even if they were not explicitly closed.
  PathMetrics computeMetrics({bool forceClosed = false});
}

base class _NativePath extends NativeFieldWrapperClass1 implements Path {
  /// Create a new empty [Path] object.
  _NativePath() {
    _constructor();
  }

  /// Avoids creating a new native backing for the path for methods that will
  /// create it later, such as [Path.from], [shift] and [transform].
  _NativePath._();

  @Native<Void Function(Handle)>(symbol: 'Path::Create')
  external void _constructor();

  @Native<Void Function(Pointer<Void>, Handle)>(symbol: 'Path::clone')
  external void _clone(Path outPath);

  @override
  PathFillType get fillType => PathFillType.values[_getFillType()];
  @override
  set fillType(PathFillType value) => _setFillType(value.index);

  @Native<Int32 Function(Pointer<Void>)>(symbol: 'Path::getFillType', isLeaf: true)
  external int _getFillType();

  @Native<Void Function(Pointer<Void>, Int32)>(symbol: 'Path::setFillType', isLeaf: true)
  external void _setFillType(int fillType);

  @override
  @Native<Void Function(Pointer<Void>, Double, Double)>(symbol: 'Path::moveTo', isLeaf: true)
  external void moveTo(double x, double y);

  @override
  @Native<Void Function(Pointer<Void>, Double, Double)>(
    symbol: 'Path::relativeMoveTo',
    isLeaf: true,
  )
  external void relativeMoveTo(double dx, double dy);

  @override
  @Native<Void Function(Pointer<Void>, Double, Double)>(symbol: 'Path::lineTo', isLeaf: true)
  external void lineTo(double x, double y);

  @override
  @Native<Void Function(Pointer<Void>, Double, Double)>(
    symbol: 'Path::relativeLineTo',
    isLeaf: true,
  )
  external void relativeLineTo(double dx, double dy);

  @override
  @Native<Void Function(Pointer<Void>, Double, Double, Double, Double)>(
    symbol: 'Path::quadraticBezierTo',
    isLeaf: true,
  )
  external void quadraticBezierTo(double x1, double y1, double x2, double y2);

  @override
  @Native<Void Function(Pointer<Void>, Double, Double, Double, Double)>(
    symbol: 'Path::relativeQuadraticBezierTo',
    isLeaf: true,
  )
  external void relativeQuadraticBezierTo(double x1, double y1, double x2, double y2);

  @override
  @Native<Void Function(Pointer<Void>, Double, Double, Double, Double, Double, Double)>(
    symbol: 'Path::cubicTo',
    isLeaf: true,
  )
  external void cubicTo(double x1, double y1, double x2, double y2, double x3, double y3);

  @override
  @Native<Void Function(Pointer<Void>, Double, Double, Double, Double, Double, Double)>(
    symbol: 'Path::relativeCubicTo',
    isLeaf: true,
  )
  external void relativeCubicTo(double x1, double y1, double x2, double y2, double x3, double y3);

  @override
  @Native<Void Function(Pointer<Void>, Double, Double, Double, Double, Double)>(
    symbol: 'Path::conicTo',
    isLeaf: true,
  )
  external void conicTo(double x1, double y1, double x2, double y2, double w);

  @override
  @Native<Void Function(Pointer<Void>, Double, Double, Double, Double, Double)>(
    symbol: 'Path::relativeConicTo',
    isLeaf: true,
  )
  external void relativeConicTo(double x1, double y1, double x2, double y2, double w);

  @override
  void arcTo(Rect rect, double startAngle, double sweepAngle, bool forceMoveTo) {
    assert(_rectIsValid(rect));
    _arcTo(rect.left, rect.top, rect.right, rect.bottom, startAngle, sweepAngle, forceMoveTo);
  }

  @Native<Void Function(Pointer<Void>, Double, Double, Double, Double, Double, Double, Bool)>(
    symbol: 'Path::arcTo',
    isLeaf: true,
  )
  external void _arcTo(
    double left,
    double top,
    double right,
    double bottom,
    double startAngle,
    double sweepAngle,
    bool forceMoveTo,
  );

  @override
  void arcToPoint(
    Offset arcEnd, {
    Radius radius = Radius.zero,
    double rotation = 0.0,
    bool largeArc = false,
    bool clockwise = true,
  }) {
    assert(_offsetIsValid(arcEnd));
    assert(_radiusIsValid(radius));
    _arcToPoint(arcEnd.dx, arcEnd.dy, radius.x, radius.y, rotation, largeArc, clockwise);
  }

  @Native<Void Function(Pointer<Void>, Double, Double, Double, Double, Double, Bool, Bool)>(
    symbol: 'Path::arcToPoint',
    isLeaf: true,
  )
  external void _arcToPoint(
    double arcEndX,
    double arcEndY,
    double radiusX,
    double radiusY,
    double rotation,
    bool largeArc,
    bool clockwise,
  );

  @override
  void relativeArcToPoint(
    Offset arcEndDelta, {
    Radius radius = Radius.zero,
    double rotation = 0.0,
    bool largeArc = false,
    bool clockwise = true,
  }) {
    assert(_offsetIsValid(arcEndDelta));
    assert(_radiusIsValid(radius));
    _relativeArcToPoint(
      arcEndDelta.dx,
      arcEndDelta.dy,
      radius.x,
      radius.y,
      rotation,
      largeArc,
      clockwise,
    );
  }

  @Native<Void Function(Pointer<Void>, Double, Double, Double, Double, Double, Bool, Bool)>(
    symbol: 'Path::relativeArcToPoint',
    isLeaf: true,
  )
  external void _relativeArcToPoint(
    double arcEndX,
    double arcEndY,
    double radiusX,
    double radiusY,
    double rotation,
    bool largeArc,
    bool clockwise,
  );

  @override
  void addRect(Rect rect) {
    assert(_rectIsValid(rect));
    _addRect(rect.left, rect.top, rect.right, rect.bottom);
  }

  @Native<Void Function(Pointer<Void>, Double, Double, Double, Double)>(
    symbol: 'Path::addRect',
    isLeaf: true,
  )
  external void _addRect(double left, double top, double right, double bottom);

  @override
  void addOval(Rect oval) {
    assert(_rectIsValid(oval));
    _addOval(oval.left, oval.top, oval.right, oval.bottom);
  }

  @Native<Void Function(Pointer<Void>, Double, Double, Double, Double)>(
    symbol: 'Path::addOval',
    isLeaf: true,
  )
  external void _addOval(double left, double top, double right, double bottom);

  @override
  void addArc(Rect oval, double startAngle, double sweepAngle) {
    assert(_rectIsValid(oval));
    _addArc(oval.left, oval.top, oval.right, oval.bottom, startAngle, sweepAngle);
  }

  @Native<Void Function(Pointer<Void>, Double, Double, Double, Double, Double, Double)>(
    symbol: 'Path::addArc',
    isLeaf: true,
  )
  external void _addArc(
    double left,
    double top,
    double right,
    double bottom,
    double startAngle,
    double sweepAngle,
  );

  @override
  void addPolygon(List<Offset> points, bool close) {
    _addPolygon(_encodePointList(points), close);
  }

  @Native<Void Function(Pointer<Void>, Handle, Bool)>(symbol: 'Path::addPolygon')
  external void _addPolygon(Float32List points, bool close);

  @override
  void addRRect(RRect rrect) {
    assert(_rrectIsValid(rrect));
    _addRRect(rrect._getValue32());
  }

  @Native<Void Function(Pointer<Void>, Handle)>(symbol: 'Path::addRRect')
  external void _addRRect(Float32List rrect);

  @override
  void addRSuperellipse(RSuperellipse rsuperellipse) {
    assert(_rsuperellipseIsValid(rsuperellipse));
    _addRSuperellipse(rsuperellipse._native());
  }

  @Native<Void Function(Pointer<Void>, Pointer<Void>)>(symbol: 'Path::addRSuperellipse')
  external void _addRSuperellipse(_NativeRSuperellipse rsuperellipse);

  @override
  void addPath(Path path, Offset offset, {Float64List? matrix4}) {
    assert(_offsetIsValid(offset));
    if (matrix4 != null) {
      assert(_matrix4IsValid(matrix4));
      _addPathWithMatrix(path as _NativePath, offset.dx, offset.dy, matrix4);
    } else {
      _addPath(path as _NativePath, offset.dx, offset.dy);
    }
  }

  @Native<Void Function(Pointer<Void>, Pointer<Void>, Double, Double)>(symbol: 'Path::addPath')
  external void _addPath(_NativePath path, double dx, double dy);

  @Native<Void Function(Pointer<Void>, Pointer<Void>, Double, Double, Handle)>(
    symbol: 'Path::addPathWithMatrix',
  )
  external void _addPathWithMatrix(_NativePath path, double dx, double dy, Float64List matrix);

  @override
  void extendWithPath(Path path, Offset offset, {Float64List? matrix4}) {
    assert(_offsetIsValid(offset));
    if (matrix4 != null) {
      assert(_matrix4IsValid(matrix4));
      _extendWithPathAndMatrix(path as _NativePath, offset.dx, offset.dy, matrix4);
    } else {
      _extendWithPath(path as _NativePath, offset.dx, offset.dy);
    }
  }

  @Native<Void Function(Pointer<Void>, Pointer<Void>, Double, Double)>(
    symbol: 'Path::extendWithPath',
  )
  external void _extendWithPath(_NativePath path, double dx, double dy);

  @Native<Void Function(Pointer<Void>, Pointer<Void>, Double, Double, Handle)>(
    symbol: 'Path::extendWithPathAndMatrix',
  )
  external void _extendWithPathAndMatrix(
    _NativePath path,
    double dx,
    double dy,
    Float64List matrix,
  );

  @override
  @Native<Void Function(Pointer<Void>)>(symbol: 'Path::close', isLeaf: true)
  external void close();

  @override
  @Native<Void Function(Pointer<Void>)>(symbol: 'Path::reset', isLeaf: true)
  external void reset();

  @override
  bool contains(Offset point) {
    assert(_offsetIsValid(point));
    return _contains(point.dx, point.dy);
  }

  @Native<Bool Function(Pointer<Void>, Double, Double)>(symbol: 'Path::contains', isLeaf: true)
  external bool _contains(double x, double y);

  @override
  Path shift(Offset offset) {
    assert(_offsetIsValid(offset));
    final path = _NativePath._();
    _shift(path, offset.dx, offset.dy);
    return path;
  }

  @Native<Void Function(Pointer<Void>, Handle, Double, Double)>(symbol: 'Path::shift')
  external void _shift(Path outPath, double dx, double dy);

  @override
  Path transform(Float64List matrix4) {
    assert(_matrix4IsValid(matrix4));
    final path = _NativePath._();
    _transform(path, matrix4);
    return path;
  }

  @Native<Void Function(Pointer<Void>, Handle, Handle)>(symbol: 'Path::transform')
  external void _transform(Path outPath, Float64List matrix4);

  @override
  Rect getBounds() {
    final Float32List rect = _getBounds();
    return Rect.fromLTRB(rect[0], rect[1], rect[2], rect[3]);
  }

  @Native<Handle Function(Pointer<Void>)>(symbol: 'Path::getBounds')
  external Float32List _getBounds();

  @Native<Bool Function(Pointer<Void>, Pointer<Void>, Pointer<Void>, Int32)>(symbol: 'Path::op')
  external bool _op(_NativePath path1, _NativePath path2, int operation);

  @override
  PathMetrics computeMetrics({bool forceClosed = false}) {
    return PathMetrics._(this, forceClosed);
  }

  @override
  String toString() => 'Path';
}

/// The geometric description of a tangent: the angle at a point.
///
/// See also:
///  * [PathMetric.getTangentForOffset], which returns the tangent of an offset along a path.
class Tangent {
  /// Creates a [Tangent] with the given values.
  ///
  /// The arguments must not be null.
  const Tangent(this.position, this.vector);

  /// Creates a [Tangent] based on the angle rather than the vector.
  ///
  /// The [vector] is computed to be the unit vector at the given angle, interpreted
  /// as clockwise radians from the x axis.
  factory Tangent.fromAngle(Offset position, double angle) {
    return Tangent(position, Offset(math.cos(angle), math.sin(angle)));
  }

  /// Position of the tangent.
  ///
  /// When used with [PathMetric.getTangentForOffset], this represents the precise
  /// position that the given offset along the path corresponds to.
  final Offset position;

  /// The vector of the curve at [position].
  ///
  /// When used with [PathMetric.getTangentForOffset], this is the vector of the
  /// curve that is at the given offset along the path (i.e. the direction of the
  /// curve at [position]).
  final Offset vector;

  /// The direction of the curve at [position].
  ///
  /// When used with [PathMetric.getTangentForOffset], this is the angle of the
  /// curve that is the given offset along the path (i.e. the direction of the
  /// curve at [position]).
  ///
  /// This value is in radians, with 0.0 meaning pointing along the x axis in
  /// the positive x-axis direction, positive numbers pointing downward toward
  /// the negative y-axis, i.e. in a clockwise direction, and negative numbers
  /// pointing upward toward the positive y-axis, i.e. in a counter-clockwise
  /// direction.
  // flip the sign to be consistent with [Path.arcTo]'s `sweepAngle`
  double get angle => -math.atan2(vector.dy, vector.dx);
}

/// An iterable collection of [PathMetric] objects describing a [Path].
///
/// A [PathMetrics] object is created by using the [Path.computeMetrics] method,
/// and represents the path as it stood at the time of the call. Subsequent
/// modifications of the path do not affect the [PathMetrics] object.
///
/// Each path metric corresponds to a segment, or contour, of a path.
///
/// For example, a path consisting of a [Path.lineTo], a [Path.moveTo], and
/// another [Path.lineTo] will contain two contours and thus be represented by
/// two [PathMetric] objects.
///
/// This iterable does not memoize. Callers who need to traverse the list
/// multiple times, or who need to randomly access elements of the list, should
/// use [toList] on this object.
class PathMetrics extends collection.IterableBase<PathMetric> {
  PathMetrics._(Path path, bool forceClosed)
    : _iterator = PathMetricIterator._(_PathMeasure(path as _NativePath, forceClosed));

  final Iterator<PathMetric> _iterator;

  @override
  Iterator<PathMetric> get iterator => _iterator;
}

/// Used by [PathMetrics] to track iteration from one segment of a path to the
/// next for measurement.
class PathMetricIterator implements Iterator<PathMetric> {
  PathMetricIterator._(this._pathMeasure);

  PathMetric? _pathMetric;
  final _PathMeasure _pathMeasure;

  @override
  PathMetric get current {
    final PathMetric? currentMetric = _pathMetric;
    if (currentMetric == null) {
      throw RangeError(
        'PathMetricIterator is not pointing to a PathMetric. This can happen in two situations:\n'
        '- The iteration has not started yet. If so, call "moveNext" to start iteration.\n'
        '- The iterator ran out of elements. If so, check that "moveNext" returns true prior to calling "current".',
      );
    }
    return currentMetric;
  }

  @override
  bool moveNext() {
    if (_pathMeasure._nextContour()) {
      _pathMetric = PathMetric._(_pathMeasure);
      return true;
    }
    _pathMetric = null;
    return false;
  }
}

/// Utilities for measuring a [Path] and extracting sub-paths.
///
/// Iterate over the object returned by [Path.computeMetrics] to obtain
/// [PathMetric] objects. Callers that want to randomly access elements or
/// iterate multiple times should use `path.computeMetrics().toList()`, since
/// [PathMetrics] does not memoize.
///
/// Once created, the metrics are only valid for the path as it was specified
/// when [Path.computeMetrics] was called. If additional contours are added or
/// any contours are updated, the metrics need to be recomputed. Previously
/// created metrics will still refer to a snapshot of the path at the time they
/// were computed, rather than to the actual metrics for the new mutations to
/// the path.
class PathMetric {
  PathMetric._(this._measure)
    : length = _measure.length(_measure.currentContourIndex),
      isClosed = _measure.isClosed(_measure.currentContourIndex),
      contourIndex = _measure.currentContourIndex;

  /// Return the total length of the current contour.
  ///
  /// The length may be calculated from an approximation of the geometry
  /// originally added. For this reason, it is not recommended to rely on
  /// this property for mathematically correct lengths of common shapes.
  final double length;

  /// Whether the contour is closed.
  ///
  /// Returns true if the contour ends with a call to [Path.close] (which may
  /// have been implied when using methods like [Path.addRect]) or if
  /// `forceClosed` was specified as true in the call to [Path.computeMetrics].
  /// Returns false otherwise.
  final bool isClosed;

  /// The zero-based index of the contour.
  ///
  /// [Path] objects are made up of zero or more contours. The first contour is
  /// created once a drawing command (e.g. [Path.lineTo]) is issued. A
  /// [Path.moveTo] command after a drawing command may create a new contour,
  /// although it may not if optimizations are applied that determine the move
  /// command did not actually result in moving the pen.
  ///
  /// This property is only valid with reference to its original iterator and
  /// the contours of the path at the time the path's metrics were computed. If
  /// additional contours were added or existing contours updated, this metric
  /// will be invalid for the current state of the path.
  final int contourIndex;

  final _PathMeasure _measure;

  /// Computes the position of the current contour at the given offset, and the
  /// angle of the path at that point.
  ///
  /// For example, calling this method with a distance of 1.41 for a line from
  /// 0.0,0.0 to 2.0,2.0 would give a point 1.0,1.0 and the angle 45 degrees
  /// (but in radians).
  ///
  /// Returns null if the contour has zero [length].
  ///
  /// The distance is clamped to the [length] of the current contour.
  Tangent? getTangentForOffset(double distance) {
    return _measure.getTangentForOffset(contourIndex, distance);
  }

  /// Given a start and end distance, return the intervening segment(s).
  ///
  /// `start` and `end` are clamped to legal values (0..[length])
  /// Begin the segment with a moveTo if `startWithMoveTo` is true.
  Path extractPath(double start, double end, {bool startWithMoveTo = true}) {
    return _measure.extractPath(contourIndex, start, end, startWithMoveTo: startWithMoveTo);
  }

  @override
  String toString() =>
      'PathMetric(length: $length, isClosed: $isClosed, contourIndex: $contourIndex)';
}

base class _PathMeasure extends NativeFieldWrapperClass1 {
  _PathMeasure(_NativePath path, bool forceClosed) {
    _constructor(path, forceClosed);
  }

  @Native<Void Function(Handle, Pointer<Void>, Bool)>(symbol: 'PathMeasure::Create')
  external void _constructor(_NativePath path, bool forceClosed);

  double length(int contourIndex) {
    assert(
      contourIndex <= currentContourIndex,
      'Iterator must be advanced before index $contourIndex can be used.',
    );
    return _length(contourIndex);
  }

  @Native<Double Function(Pointer<Void>, Int32)>(symbol: 'PathMeasure::getLength', isLeaf: true)
  external double _length(int contourIndex);

  Tangent? getTangentForOffset(int contourIndex, double distance) {
    assert(
      contourIndex <= currentContourIndex,
      'Iterator must be advanced before index $contourIndex can be used.',
    );
    final Float32List posTan = _getPosTan(contourIndex, distance);
    // first entry == 0 indicates that Skia returned false
    if (posTan[0] == 0.0) {
      return null;
    } else {
      return Tangent(Offset(posTan[1], posTan[2]), Offset(posTan[3], posTan[4]));
    }
  }

  @Native<Handle Function(Pointer<Void>, Int32, Double)>(symbol: 'PathMeasure::getPosTan')
  external Float32List _getPosTan(int contourIndex, double distance);

  Path extractPath(int contourIndex, double start, double end, {bool startWithMoveTo = true}) {
    assert(
      contourIndex <= currentContourIndex,
      'Iterator must be advanced before index $contourIndex can be used.',
    );
    final path = _NativePath._();
    _extractPath(path, contourIndex, start, end, startWithMoveTo);
    return path;
  }

  @Native<Void Function(Pointer<Void>, Handle, Int32, Double, Double, Bool)>(
    symbol: 'PathMeasure::getSegment',
  )
  external void _extractPath(
    Path outPath,
    int contourIndex,
    double start,
    double end,
    bool startWithMoveTo,
  );

  bool isClosed(int contourIndex) {
    assert(
      contourIndex <= currentContourIndex,
      'Iterator must be advanced before index $contourIndex can be used.',
    );
    return _isClosed(contourIndex);
  }

  @Native<Bool Function(Pointer<Void>, Int32)>(symbol: 'PathMeasure::isClosed', isLeaf: true)
  external bool _isClosed(int contourIndex);

  // Move to the next contour in the path.
  //
  // A path can have a next contour if [Path.moveTo] was called after drawing began.
  // Return true if one exists, or false.
  bool _nextContour() {
    final bool next = _nativeNextContour();
    if (next) {
      currentContourIndex++;
    }
    return next;
  }

  @Native<Bool Function(Pointer<Void>)>(symbol: 'PathMeasure::nextContour', isLeaf: true)
  external bool _nativeNextContour();

  /// The index of the current contour in the list of contours in the path.
  ///
  /// [nextContour] will increment this to the zero based index.
  int currentContourIndex = -1;
}

/// Styles to use for blurs in [MaskFilter] objects.
// These enum values must be kept in sync with DlBlurStyle.
enum BlurStyle {
  // These mirror DlBlurStyle and must be kept in sync.

  /// Fuzzy inside and outside. This is useful for painting shadows that are
  /// offset from the shape that ostensibly is casting the shadow.
  normal,

  /// Solid inside, fuzzy outside. This corresponds to drawing the shape, and
  /// additionally drawing the blur. This can make objects appear brighter,
  /// maybe even as if they were fluorescent.
  solid,

  /// Nothing inside, fuzzy outside. This is useful for painting shadows for
  /// partially transparent shapes, when they are painted separately but without
  /// an offset, so that the shadow doesn't paint below the shape.
  outer,

  /// Fuzzy inside, nothing outside. This can make shapes appear to be lit from
  /// within.
  inner,
}

/// A mask filter to apply to shapes as they are painted. A mask filter is a
/// function that takes a bitmap of color pixels, and returns another bitmap of
/// color pixels.
///
/// Instances of this class are used with [Paint.maskFilter] on [Paint] objects.
class MaskFilter {
  /// Creates a mask filter that takes the shape being drawn and blurs it.
  ///
  /// This is commonly used to approximate shadows.
  ///
  /// The `style` argument controls the kind of effect to draw; see [BlurStyle].
  ///
  /// The `sigma` argument controls the size of the effect. It is the standard
  /// deviation of the Gaussian blur to apply. The value must be greater than
  /// zero. The sigma corresponds to very roughly half the radius of the effect
  /// in pixels.
  ///
  /// A blur is an expensive operation and should therefore be used sparingly.
  ///
  /// The arguments must not be null.
  ///
  /// See also:
  ///
  ///  * [Canvas.drawShadow], which is a more efficient way to draw shadows.
  const MaskFilter.blur(this._style, this._sigma);

  final BlurStyle _style;
  final double _sigma;

  // The type of MaskFilter class to create for flutter::DisplayList.
  // These constants must be kept in sync with MaskFilterType in paint.cc.
  static const int _TypeNone = 0; // null
  static const int _TypeBlur = 1; // DlBlurMaskFilter

  @override
  bool operator ==(Object other) {
    return other is MaskFilter && other._style == _style && other._sigma == _sigma;
  }

  @override
  int get hashCode => Object.hash(_style, _sigma);

  @override
  String toString() => 'MaskFilter.blur($_style, ${_sigma.toStringAsFixed(1)})';
}

abstract class _ColorTransform {
  Color transform(Color color, ColorSpace resultColorSpace);
}

class _IdentityColorTransform implements _ColorTransform {
  const _IdentityColorTransform();
  @override
  Color transform(Color color, ColorSpace resultColorSpace) => color;
}

class _ClampTransform implements _ColorTransform {
  const _ClampTransform(this.child);
  final _ColorTransform child;
  @override
  Color transform(Color color, ColorSpace resultColorSpace) {
    return Color.from(
      alpha: clampDouble(color.a, 0, 1),
      red: clampDouble(color.r, 0, 1),
      green: clampDouble(color.g, 0, 1),
      blue: clampDouble(color.b, 0, 1),
      colorSpace: resultColorSpace,
    );
  }
}

// sRGB standard constants for transfer functions.
// See https://en.wikipedia.org/wiki/SRGB.
const double _kSrgbGamma = 2.4;
const double _kSrgbLinearThreshold = 0.04045;
const double _kSrgbLinearSlope = 12.92;
const double _kSrgbEncodedOffset = 0.055;
const double _kSrgbEncodedDivisor = 1.055;
const double _kSrgbLinearToEncodedThreshold = 0.0031308;

/// sRGB electro-optical transfer function (gamma decode to linear).
double _srgbEOTF(double v) {
  if (v <= _kSrgbLinearThreshold) {
    return v / _kSrgbLinearSlope;
  }
  return math.pow((v + _kSrgbEncodedOffset) / _kSrgbEncodedDivisor, _kSrgbGamma).toDouble();
}

/// sRGB opto-electronic transfer function (linear to gamma encode).
double _srgbOETF(double v) {
  if (v <= _kSrgbLinearToEncodedThreshold) {
    return v * _kSrgbLinearSlope;
  }
  return _kSrgbEncodedDivisor * math.pow(v, 1.0 / _kSrgbGamma).toDouble() - _kSrgbEncodedOffset;
}

/// Extended versions that handle negative values by mirroring.
double _srgbEOTFExtended(double v) {
  return v < 0.0 ? -_srgbEOTF(-v) : _srgbEOTF(v);
}

double _srgbOETFExtended(double v) {
  return v < 0.0 ? -_srgbOETF(-v) : _srgbOETF(v);
}

/// Display P3 to sRGB 3x3 matrix in linear space.
/// M = sRGB_XYZ_to_RGB * P3_RGB_to_XYZ
const List<double> _kP3ToSrgbLinear = <double>[
  1.2249401,
  -0.2249402,
  0.0,
  -0.0420569,
  1.0420571,
  0.0,
  -0.0196376,
  -0.0786507,
  1.0982884,
];

/// sRGB to Display P3 3x3 matrix in linear space (inverse of [_kP3ToSrgbLinear]).
const List<double> _kSrgbToP3Linear = <double>[
  0.8224622,
  0.1775380,
  0.0,
  0.0331942,
  0.9668058,
  0.0,
  0.0170806,
  0.0723974,
  0.9105220,
];

/// Converts Display P3 (gamma-encoded) to extended sRGB (gamma-encoded).
/// Pipeline: EOTF(decode) -> 3x3 matrix -> OETF(encode).
class _P3ToSrgbTransform implements _ColorTransform {
  const _P3ToSrgbTransform();

  @override
  Color transform(Color color, ColorSpace resultColorSpace) {
    final double rLin = _srgbEOTFExtended(color.r);
    final double gLin = _srgbEOTFExtended(color.g);
    final double bLin = _srgbEOTFExtended(color.b);

    final double rOut =
        _kP3ToSrgbLinear[0] * rLin + _kP3ToSrgbLinear[1] * gLin + _kP3ToSrgbLinear[2] * bLin;
    final double gOut =
        _kP3ToSrgbLinear[3] * rLin + _kP3ToSrgbLinear[4] * gLin + _kP3ToSrgbLinear[5] * bLin;
    final double bOut =
        _kP3ToSrgbLinear[6] * rLin + _kP3ToSrgbLinear[7] * gLin + _kP3ToSrgbLinear[8] * bLin;

    return Color.from(
      alpha: color.a,
      red: _srgbOETFExtended(rOut),
      green: _srgbOETFExtended(gOut),
      blue: _srgbOETFExtended(bOut),
      colorSpace: resultColorSpace,
    );
  }
}

/// Converts sRGB (gamma-encoded) to Display P3 (gamma-encoded).
/// Pipeline: EOTF(decode) -> 3x3 matrix -> OETF(encode).
class _SrgbToP3Transform implements _ColorTransform {
  const _SrgbToP3Transform();

  @override
  Color transform(Color color, ColorSpace resultColorSpace) {
    final double rLin = _srgbEOTFExtended(color.r);
    final double gLin = _srgbEOTFExtended(color.g);
    final double bLin = _srgbEOTFExtended(color.b);

    final double rOut =
        _kSrgbToP3Linear[0] * rLin + _kSrgbToP3Linear[1] * gLin + _kSrgbToP3Linear[2] * bLin;
    final double gOut =
        _kSrgbToP3Linear[3] * rLin + _kSrgbToP3Linear[4] * gLin + _kSrgbToP3Linear[5] * bLin;
    final double bOut =
        _kSrgbToP3Linear[6] * rLin + _kSrgbToP3Linear[7] * gLin + _kSrgbToP3Linear[8] * bLin;

    return Color.from(
      alpha: color.a,
      red: _srgbOETFExtended(rOut),
      green: _srgbOETFExtended(gOut),
      blue: _srgbOETFExtended(bOut),
      colorSpace: resultColorSpace,
    );
  }
}

_ColorTransform _getColorTransform(ColorSpace source, ColorSpace destination) {
  switch (source) {
    case ColorSpace.sRGB:
      switch (destination) {
        case ColorSpace.sRGB:
          return const _IdentityColorTransform();
        case ColorSpace.extendedSRGB:
          return const _IdentityColorTransform();
        case ColorSpace.displayP3:
          return const _SrgbToP3Transform();
      }
    case ColorSpace.extendedSRGB:
      switch (destination) {
        case ColorSpace.sRGB:
          return const _ClampTransform(_IdentityColorTransform());
        case ColorSpace.extendedSRGB:
          return const _IdentityColorTransform();
        case ColorSpace.displayP3:
          return const _ClampTransform(_SrgbToP3Transform());
      }
    case ColorSpace.displayP3:
      switch (destination) {
        case ColorSpace.sRGB:
          return const _ClampTransform(_P3ToSrgbTransform());
        case ColorSpace.extendedSRGB:
          return const _P3ToSrgbTransform();
        case ColorSpace.displayP3:
          return const _IdentityColorTransform();
      }
  }
}

/// A description of a color filter to apply when drawing a shape or compositing
/// a layer with a particular [Paint]. A color filter is a function that takes
/// two colors, and outputs one color. When applied during compositing, it is
/// independently applied to each pixel of the layer being drawn before the
/// entire layer is merged with the destination.
///
/// Instances of this class are used with [Paint.colorFilter] on [Paint]
/// objects.
class ColorFilter implements ImageFilter {
  /// Creates a color filter that applies the blend mode given as the second
  /// argument. The source color is the one given as the first argument, and the
  /// destination color is the one from the layer being composited.
  ///
  /// The output of this filter is then composited into the background according
  /// to the [Paint.blendMode], using the output of this filter as the source
  /// and the background as the destination.
  const ColorFilter.mode(Color color, BlendMode blendMode)
    : _color = color,
      _blendMode = blendMode,
      _matrix = null,
      _type = _kTypeMode;

  /// Construct a color filter from a 4x5 row-major matrix. The matrix is
  /// interpreted as a 5x5 matrix, where the fifth row is the identity
  /// configuration.
  ///
  /// Every pixel's color value, represented as an `[R, G, B, A]`, is matrix
  /// multiplied to create a new color:
  ///
  ///     | R' |   | a00 a01 a02 a03 a04 |   | R |
  ///     | G' |   | a10 a11 a12 a13 a14 |   | G |
  ///     | B' | = | a20 a21 a22 a23 a24 | * | B |
  ///     | A' |   | a30 a31 a32 a33 a34 |   | A |
  ///     | 1  |   |  0   0   0   0   1  |   | 1 |
  ///
  /// The matrix is in row-major order and the translation column is specified
  /// in unnormalized, 0...255, space. For example, the identity matrix is:
  ///
  /// ```dart
  /// const ColorFilter identity = ColorFilter.matrix(<double>[
  ///   1, 0, 0, 0, 0,
  ///   0, 1, 0, 0, 0,
  ///   0, 0, 1, 0, 0,
  ///   0, 0, 0, 1, 0,
  /// ]);
  /// ```
  ///
  /// ## Examples
  ///
  /// An inversion color matrix:
  ///
  /// ```dart
  /// const ColorFilter invert = ColorFilter.matrix(<double>[
  ///   -1,  0,  0, 0, 255,
  ///    0, -1,  0, 0, 255,
  ///    0,  0, -1, 0, 255,
  ///    0,  0,  0, 1,   0,
  /// ]);
  /// ```
  ///
  /// A sepia-toned color matrix (values based on the [Filter Effects Spec](https://www.w3.org/TR/filter-effects-1/#sepiaEquivalent)):
  ///
  /// ```dart
  /// const ColorFilter sepia = ColorFilter.matrix(<double>[
  ///   0.393, 0.769, 0.189, 0, 0,
  ///   0.349, 0.686, 0.168, 0, 0,
  ///   0.272, 0.534, 0.131, 0, 0,
  ///   0,     0,     0,     1, 0,
  /// ]);
  /// ```
  ///
  /// A greyscale color filter (values based on the [Filter Effects Spec](https://www.w3.org/TR/filter-effects-1/#grayscaleEquivalent)):
  ///
  /// ```dart
  /// const ColorFilter greyscale = ColorFilter.matrix(<double>[
  ///   0.2126, 0.7152, 0.0722, 0, 0,
  ///   0.2126, 0.7152, 0.0722, 0, 0,
  ///   0.2126, 0.7152, 0.0722, 0, 0,
  ///   0,      0,      0,      1, 0,
  /// ]);
  /// ```
  const ColorFilter.matrix(List<double> matrix)
    : _color = null,
      _blendMode = null,
      _matrix = matrix,
      _type = _kTypeMatrix;

  /// Construct a color filter that applies the sRGB gamma curve to the RGB
  /// channels.
  const ColorFilter.linearToSrgbGamma()
    : _color = null,
      _blendMode = null,
      _matrix = null,
      _type = _kTypeLinearToSrgbGamma;

  /// Creates a color filter that applies the inverse of the sRGB gamma curve
  /// to the RGB channels.
  const ColorFilter.srgbToLinearGamma()
    : _color = null,
      _blendMode = null,
      _matrix = null,
      _type = _kTypeSrgbToLinearGamma;

  /// Creates a color filter that applies the given saturation to the RGB
  /// channels.
  factory ColorFilter.saturation(double saturation) {
    const rLuminance = 0.2126;
    const gLuminance = 0.7152;
    const bLuminance = 0.0722;
    final double invSat = 1 - saturation;

    return ColorFilter.matrix(<double>[
      // dart format off
      invSat * rLuminance + saturation, invSat * gLuminance,              invSat * bLuminance,              0, 0,
      invSat * rLuminance,              invSat * gLuminance + saturation, invSat * bLuminance,              0, 0,
      invSat * rLuminance,              invSat * gLuminance,              invSat * bLuminance + saturation, 0, 0,
      0,                                0,                                0,                                1, 0,
      // dart format on
    ]);
  }

  final Color? _color;
  final BlendMode? _blendMode;
  final List<double>? _matrix;
  final int _type;

  // The type of DlColorFilter class to create.
  static const int _kTypeMode = 1; // MakeModeFilter
  static const int _kTypeMatrix = 2; // MakeMatrixFilterRowMajor255
  static const int _kTypeLinearToSrgbGamma = 3; // MakeLinearToSRGBGamma
  static const int _kTypeSrgbToLinearGamma = 4; // MakeSRGBToLinearGamma

  // DlColorImageFilter
  @override
  _ImageFilter _toNativeImageFilter() => _ImageFilter.fromColorFilter(this);

  _ColorFilter? _toNativeColorFilter() {
    switch (_type) {
      case _kTypeMode:
        if (_color == null || _blendMode == null) {
          return null;
        }
        return _ColorFilter.mode(this);
      case _kTypeMatrix:
        final List<double>? matrix = _matrix;
        if (matrix == null) {
          return null;
        }
        assert(matrix.length == 20, 'Color Matrix must have 20 entries.');
        return _ColorFilter.matrix(this);
      case _kTypeLinearToSrgbGamma:
        return _ColorFilter.linearToSrgbGamma(this);
      case _kTypeSrgbToLinearGamma:
        return _ColorFilter.srgbToLinearGamma(this);
      default:
        throw StateError('Unknown mode $_type for ColorFilter.');
    }
  }

  @override
  bool operator ==(Object other) {
    if (other.runtimeType != runtimeType) {
      return false;
    }
    return other is ColorFilter &&
        other._type == _type &&
        _listEquals<double>(other._matrix, _matrix) &&
        other._color == _color &&
        other._blendMode == _blendMode;
  }

  @override
  int get hashCode {
    final List<double>? matrix = _matrix;
    return Object.hash(_color, _blendMode, matrix == null ? null : Object.hashAll(matrix), _type);
  }

  @override
  String get debugShortDescription {
    switch (_type) {
      case _kTypeMode:
        return 'ColorFilter.mode($_color, $_blendMode)';
      case _kTypeMatrix:
        return 'ColorFilter.matrix($_matrix)';
      case _kTypeLinearToSrgbGamma:
        return 'ColorFilter.linearToSrgbGamma()';
      case _kTypeSrgbToLinearGamma:
        return 'ColorFilter.srgbToLinearGamma()';
      default:
        return 'unknow ColorFilter';
    }
  }

  @override
  String toString() {
    switch (_type) {
      case _kTypeMode:
        return 'ColorFilter.mode($_color, $_blendMode)';
      case _kTypeMatrix:
        return 'ColorFilter.matrix($_matrix)';
      case _kTypeLinearToSrgbGamma:
        return 'ColorFilter.linearToSrgbGamma()';
      case _kTypeSrgbToLinearGamma:
        return 'ColorFilter.srgbToLinearGamma()';
      default:
        return "Unknown ColorFilter type. This is an error. If you're seeing this, please file an issue at https://github.com/flutter/flutter/issues/new.";
    }
  }
}

/// A [ColorFilter] that is backed by a native DlColorFilter.
///
/// This is a private class, rather than being the implementation of the public
/// ColorFilter, because we want ColorFilter to be const constructible and
/// efficiently comparable, so that widgets can check for ColorFilter equality to
/// avoid repainting.
base class _ColorFilter extends NativeFieldWrapperClass1 {
  _ColorFilter.mode(this.creator) : assert(creator._type == ColorFilter._kTypeMode) {
    _constructor();
    _initMode(creator._color!.value, creator._blendMode!.index);
  }

  _ColorFilter.matrix(this.creator) : assert(creator._type == ColorFilter._kTypeMatrix) {
    _constructor();
    _initMatrix(Float32List.fromList(creator._matrix!));
  }
  _ColorFilter.linearToSrgbGamma(this.creator)
    : assert(creator._type == ColorFilter._kTypeLinearToSrgbGamma) {
    _constructor();
    _initLinearToSrgbGamma();
  }

  _ColorFilter.srgbToLinearGamma(this.creator)
    : assert(creator._type == ColorFilter._kTypeSrgbToLinearGamma) {
    _constructor();
    _initSrgbToLinearGamma();
  }

  /// The original Dart object that created the native wrapper, which retains
  /// the values used for the filter.
  final ColorFilter creator;

  @Native<Void Function(Handle)>(symbol: 'ColorFilter::Create')
  external void _constructor();

  @Native<Void Function(Pointer<Void>, Int32, Int32)>(symbol: 'ColorFilter::initMode', isLeaf: true)
  external void _initMode(int color, int blendMode);

  @Native<Void Function(Pointer<Void>, Handle)>(symbol: 'ColorFilter::initMatrix')
  external void _initMatrix(Float32List matrix);

  @Native<Void Function(Pointer<Void>)>(symbol: 'ColorFilter::initLinearToSrgbGamma', isLeaf: true)
  external void _initLinearToSrgbGamma();

  @Native<Void Function(Pointer<Void>)>(symbol: 'ColorFilter::initSrgbToLinearGamma', isLeaf: true)
  external void _initSrgbToLinearGamma();
}

/// A filter operation to apply to a raster image.
///
/// See also:
///
///  * [BackdropFilter], a widget that applies [ImageFilter] to its rendering.
///  * [ClipRect], a widget that limits the area affected by the [ImageFilter]
///    when used with [BackdropFilter].
///  * [ImageFiltered], a widget that applies [ImageFilter] to its children.
///  * [SceneBuilder.pushBackdropFilter], which is the low-level API for using
///    this class as a backdrop filter.
///  * [SceneBuilder.pushImageFilter], which is the low-level API for using
///    this class as a child layer filter.
abstract class ImageFilter {
  // This class is not meant to be extended; this constructor prevents extension.
  ImageFilter._(); // ignore: unused_element

  /// Creates an image filter that applies a Gaussian blur.
  ///
  /// The `sigma_x` and `sigma_y` are the standard deviation of the Gaussian
  /// kernel in the X direction and the Y direction, respectively.
  ///
  /// The `tile_mode` defines the behavior of sampling pixels at the edges when
  /// performing a standard, unbounded blur.
  ///
  /// The `bounds` argument is optional and enables "bounded blur" mode. When
  /// `bounds` is non-null, the image filter substitutes transparent black for
  /// any sample it reads from outside the defined bounding rectangle. The final
  /// weighted sum is then divided by the total weight of the non-transparent samples
  /// (the effective alpha), resulting in opaque output.
  ///
  /// The bounded mode prevents color bleeding from content adjacent to the
  /// bounds into the blurred area, and is typically used when the blur must be
  /// strictly contained within a clipped region, such as for iOS-style frosted
  /// glass effects.
  ///
  /// The `bounds` rectangle is specified in the canvas's current coordinate
  /// space and is affected by the current transform; consequently, the bounds
  /// may not be axis-aligned in the final canvas coordinates.
  factory ImageFilter.blur({
    double sigmaX = 0.0,
    double sigmaY = 0.0,
    TileMode? tileMode,
    Rect? bounds,
  }) {
    return _GaussianBlurImageFilter(
      sigmaX: sigmaX,
      sigmaY: sigmaY,
      tileMode: tileMode,
      bounds: bounds,
    );
  }

  /// Creates an image filter that dilates each input pixel's channel values
  /// to the max value within the given radii along the x and y axes.
  factory ImageFilter.dilate({double radiusX = 0.0, double radiusY = 0.0}) {
    return _DilateImageFilter(radiusX: radiusX, radiusY: radiusY);
  }

  /// Create a filter that erodes each input pixel's channel values
  /// to the minimum channel value within the given radii along the x and y axes.
  factory ImageFilter.erode({double radiusX = 0.0, double radiusY = 0.0}) {
    return _ErodeImageFilter(radiusX: radiusX, radiusY: radiusY);
  }

  /// Creates an image filter that applies a matrix transformation.
  ///
  /// For example, applying a positive scale matrix (see [Matrix4.diagonal3])
  /// when used with [BackdropFilter] would magnify the background image.
  factory ImageFilter.matrix(
    Float64List matrix4, {
    FilterQuality filterQuality = FilterQuality.medium,
  }) {
    if (matrix4.length != 16) {
      throw ArgumentError('"matrix4" must have 16 entries.');
    }
    return _MatrixImageFilter(data: Float64List.fromList(matrix4), filterQuality: filterQuality);
  }

  /// Composes the `inner` filter with `outer`, to combine their effects.
  ///
  /// Creates a single [ImageFilter] that when applied, has the same effect as
  /// subsequently applying `inner` and `outer`, i.e.,
  /// result = outer(inner(source)).
  factory ImageFilter.compose({required ImageFilter outer, required ImageFilter inner}) {
    return _ComposeImageFilter(innerFilter: inner, outerFilter: outer);
  }

  /// Creates an image filter from a [FragmentShader].
  ///
  /// > [!WARNING]
  /// > This API is only supported when using the Impeller rendering engine.
  /// > On other backends, an [UnsupportedError] will be thrown.
  ///
  /// > To check at runtime whether this API is supported, use [isShaderFilterSupported].
  ///
  /// Example usage:
  ///
  /// ```dart
  /// if (ui.ImageFilter.isShaderFilterSupported) {
  ///   // Use the filter...
  /// }
  /// ```
  ///
  /// The fragment shader provided here has additional requirements to be used
  /// by the engine for filtering. The first uniform value must be a vec2, this
  /// will be set by the engine to the size of the bound texture. There must
  /// also be at least one sampler2D uniform, the first of which will be set by
  /// the engine to contain the filter input.
  ///
  /// When Impeller uses the OpenGL(ES) backend, the y-axis direction is
  /// reversed. Custom fragment shaders must invert the y-axis on
  /// GLES or they will render upside-down.
  ///
  /// For example, the following is a valid fragment shader that can be used
  /// with this API. Note that the uniform names are not required to have any
  /// particular value.
  ///
  /// ```glsl
  /// #include <flutter/runtime_effect.glsl>
  ///
  /// uniform vec2 u_size;
  /// uniform float u_time;
  ///
  /// uniform sampler2D u_texture_input;
  ///
  /// out vec4 frag_color;
  ///
  /// void main() {
  ///   vec2 uv = FlutterFragCoord().xy / u_size;
  /// // Reverse y axis for OpenGL backend.
  /// #ifdef IMPELLER_TARGET_OPENGLES
  ///   uv.y = 1.0 - uv.y
  /// #endif
  ///   frag_color = texture(u_texture_input, uv) * u_time;
  ///
  /// }
  ///
  /// ```
  factory ImageFilter.shader(FragmentShader shader) {
    if (!_impellerEnabled) {
      throw UnsupportedError('ImageFilter.shader only supported with Impeller rendering engine.');
    }
    final bool invalidFloats = shader._floats.length < 2;
    final bool invalidSampler = !shader._validateImageFilter();
    if (invalidFloats || invalidSampler) {
      final buffer = StringBuffer(
        'ImageFilter.shader requires that the first uniform is a vec2 and at '
        'least one sampler uniform is present.\n',
      );
      if (invalidFloats) {
        buffer.write('The shader has fewer than two float uniforms.\n');
      }
      if (invalidSampler) {
        buffer.write('The shader is missing a sampler uniform.\n');
      }
      throw StateError(buffer.toString());
    }
    return _FragmentShaderImageFilter(shader);
  }

  /// Whether [ImageFilter.shader] is supported on the current backend.
  ///
  /// > [!WARNING]
  /// > This property will only return true when the Impeller rendering engine is enabled.
  /// > Attempting to create an [ImageFilter.shader] when this property is `false` will throw an [UnsupportedError].
  static bool get isShaderFilterSupported => _impellerEnabled;

  // Converts this to a native DlImageFilter. See the comments of this method in
  // subclasses for the exact type of DlImageFilter this method converts to.
  _ImageFilter _toNativeImageFilter();

  /// The description text to show when the filter is part of a composite
  /// [ImageFilter] created using [ImageFilter.compose].
  String get debugShortDescription => toString();
}

class _MatrixImageFilter implements ImageFilter {
  _MatrixImageFilter({required this.data, required this.filterQuality});

  final Float64List data;
  final FilterQuality filterQuality;

  // MakeMatrixFilterRowMajor255
  late final _ImageFilter nativeFilter = _ImageFilter.matrix(this);
  @override
  _ImageFilter _toNativeImageFilter() => nativeFilter;

  @override
  String get debugShortDescription => 'matrix($data, $filterQuality)';

  @override
  String toString() => 'ImageFilter.matrix($data, $filterQuality)';

  @override
  bool operator ==(Object other) {
    if (other.runtimeType != runtimeType) {
      return false;
    }
    return other is _MatrixImageFilter &&
        other.filterQuality == filterQuality &&
        _listEquals<double>(other.data, data);
  }

  @override
  int get hashCode => Object.hash(filterQuality, Object.hashAll(data));
}

class _GaussianBlurImageFilter implements ImageFilter {
  _GaussianBlurImageFilter({
    required this.sigmaX,
    required this.sigmaY,
    required this.tileMode,
    this.bounds,
  });

  final double sigmaX;
  final double sigmaY;
  final TileMode? tileMode;
  final Rect? bounds;

  // MakeBlurFilter
  late final _ImageFilter nativeFilter = _ImageFilter.blur(this);
  @override
  _ImageFilter _toNativeImageFilter() => nativeFilter;

  String get _modeString {
    switch (tileMode) {
      case TileMode.clamp:
        return 'clamp';
      case TileMode.mirror:
        return 'mirror';
      case TileMode.repeated:
        return 'repeated';
      case TileMode.decal:
        return 'decal';
      case null:
        return 'unspecified';
    }
  }

  @override
  String get debugShortDescription => 'blur($sigmaX, $sigmaY, $_modeString${_boundsString()})';

  String _boundsString() => bounds == null ? '' : ', bounds: $bounds';

  @override
  String toString() => 'ImageFilter.blur($sigmaX, $sigmaY, $_modeString${_boundsString()})';

  @override
  bool operator ==(Object other) {
    if (other.runtimeType != runtimeType) {
      return false;
    }
    return other is _GaussianBlurImageFilter &&
        other.sigmaX == sigmaX &&
        other.sigmaY == sigmaY &&
        other.bounds == bounds &&
        other.tileMode == tileMode;
  }

  @override
  int get hashCode => Object.hash(sigmaX, sigmaY, bounds, tileMode);
}

class _DilateImageFilter implements ImageFilter {
  _DilateImageFilter({required this.radiusX, required this.radiusY});

  final double radiusX;
  final double radiusY;

  late final _ImageFilter nativeFilter = _ImageFilter.dilate(this);
  @override
  _ImageFilter _toNativeImageFilter() => nativeFilter;

  @override
  String get debugShortDescription => 'dilate($radiusX, $radiusY)';

  @override
  String toString() => 'ImageFilter.dilate($radiusX, $radiusY)';

  @override
  bool operator ==(Object other) {
    if (other.runtimeType != runtimeType) {
      return false;
    }
    return other is _DilateImageFilter && other.radiusX == radiusX && other.radiusY == radiusY;
  }

  @override
  int get hashCode => Object.hash(radiusX, radiusY);
}

class _ErodeImageFilter implements ImageFilter {
  _ErodeImageFilter({required this.radiusX, required this.radiusY});

  final double radiusX;
  final double radiusY;

  late final _ImageFilter nativeFilter = _ImageFilter.erode(this);
  @override
  _ImageFilter _toNativeImageFilter() => nativeFilter;

  @override
  String get debugShortDescription => 'erode($radiusX, $radiusY)';

  @override
  String toString() => 'ImageFilter.erode($radiusX, $radiusY)';

  @override
  bool operator ==(Object other) {
    if (other.runtimeType != runtimeType) {
      return false;
    }
    return other is _ErodeImageFilter && other.radiusX == radiusX && other.radiusY == radiusY;
  }

  @override
  int get hashCode => Object.hash(radiusX, radiusY);
}

class _ComposeImageFilter implements ImageFilter {
  _ComposeImageFilter({required this.innerFilter, required this.outerFilter});

  final ImageFilter innerFilter;
  final ImageFilter outerFilter;

  // DlComposeImageFilter
  late final _ImageFilter nativeFilter = _ImageFilter.composed(this);
  @override
  _ImageFilter _toNativeImageFilter() => nativeFilter;

  @override
  String get debugShortDescription =>
      '${innerFilter.debugShortDescription} -> ${outerFilter.debugShortDescription}';

  @override
  String toString() => 'ImageFilter.compose(source -> $debugShortDescription -> result)';

  @override
  bool operator ==(Object other) {
    if (other.runtimeType != runtimeType) {
      return false;
    }
    return other is _ComposeImageFilter &&
        other.innerFilter == innerFilter &&
        other.outerFilter == outerFilter;
  }

  @override
  int get hashCode => Object.hash(innerFilter, outerFilter);
}

class _FragmentShaderImageFilter implements ImageFilter {
  _FragmentShaderImageFilter(this.shader);

  final FragmentShader shader;

  late final _ImageFilter nativeFilter = _ImageFilter.shader(this);

  @override
  _ImageFilter _toNativeImageFilter() => nativeFilter;

  @override
  String get debugShortDescription => 'shader';

  @override
  String toString() => 'ImageFilter.shader(Shader#${shader.hashCode})';

  @override
  bool operator ==(Object other) {
    if (other.runtimeType != runtimeType) {
      return false;
    }
    return other is _FragmentShaderImageFilter &&
        other.shader == shader &&
        _equals(nativeFilter, other.nativeFilter);
  }

  @Native<Bool Function(Handle, Handle)>(symbol: 'ImageFilter::equals')
  external static bool _equals(_ImageFilter a, _ImageFilter b);

  @override
  int get hashCode => shader.hashCode;
}

/// An [ImageFilter] that is backed by a native DlImageFilter.
///
/// This is a private class, rather than being the implementation of the public
/// ImageFilter, because we want ImageFilter to be efficiently comparable, so that
/// widgets can check for ImageFilter equality to avoid repainting.
base class _ImageFilter extends NativeFieldWrapperClass1 {
  /// Creates an image filter that applies a Gaussian blur.
  _ImageFilter.blur(_GaussianBlurImageFilter filter) : creator = filter {
    _constructor();
    final Rect bounds = filter.bounds ?? Rect.zero;
    _initBlur(
      filter.sigmaX,
      filter.sigmaY,
      filter.tileMode?.index ?? -1,
      filter.bounds != null,
      bounds.left,
      bounds.top,
      bounds.right,
      bounds.bottom,
    );
  }

  /// Creates an image filter that dilates each input pixel's channel values
  /// to the max value within the given radii along the x and y axes.
  _ImageFilter.dilate(_DilateImageFilter filter) : creator = filter {
    _constructor();
    _initDilate(filter.radiusX, filter.radiusY);
  }

  /// Create a filter that erodes each input pixel's channel values
  /// to the minimum channel value within the given radii along the x and y axes.
  _ImageFilter.erode(_ErodeImageFilter filter) : creator = filter {
    _constructor();
    _initErode(filter.radiusX, filter.radiusY);
  }

  /// Creates an image filter that applies a matrix transformation.
  ///
  /// For example, applying a positive scale matrix (see [Matrix4.diagonal3])
  /// when used with [BackdropFilter] would magnify the background image.
  _ImageFilter.matrix(_MatrixImageFilter filter) : creator = filter {
    if (filter.data.length != 16) {
      throw ArgumentError('"matrix4" must have 16 entries.');
    }
    _constructor();
    _initMatrix(filter.data, filter.filterQuality.index);
  }

  /// Converts a color filter to an image filter.
  _ImageFilter.fromColorFilter(ColorFilter filter) : creator = filter {
    _constructor();
    final _ColorFilter? nativeFilter = filter._toNativeColorFilter();
    _initColorFilter(nativeFilter);
  }

  /// Composes `_innerFilter` with `_outerFilter`.
  _ImageFilter.composed(_ComposeImageFilter filter) : creator = filter {
    _constructor();
    final _ImageFilter nativeFilterInner = filter.innerFilter._toNativeImageFilter();
    final _ImageFilter nativeFilterOuter = filter.outerFilter._toNativeImageFilter();
    _initComposed(nativeFilterOuter, nativeFilterInner);
  }

  _ImageFilter.shader(_FragmentShaderImageFilter filter) : creator = filter {
    _constructor();
    _initShader(filter.shader);
  }

  @Native<Void Function(Handle)>(symbol: 'ImageFilter::Create')
  external void _constructor();

  @Native<
    Void Function(Pointer<Void>, Double, Double, Int32, Bool, Double, Double, Double, Double)
  >(symbol: 'ImageFilter::initBlur', isLeaf: true)
  external void _initBlur(
    double sigmaX,
    double sigmaY,
    int tileMode,
    bool bounded,
    double boundsLeft,
    double boundsTop,
    double boundsRight,
    double boundsBottom,
  );

  @Native<Void Function(Pointer<Void>, Double, Double)>(
    symbol: 'ImageFilter::initDilate',
    isLeaf: true,
  )
  external void _initDilate(double radiusX, double radiusY);

  @Native<Void Function(Pointer<Void>, Double, Double)>(
    symbol: 'ImageFilter::initErode',
    isLeaf: true,
  )
  external void _initErode(double radiusX, double radiusY);

  @Native<Void Function(Pointer<Void>, Handle, Int32)>(symbol: 'ImageFilter::initMatrix')
  external void _initMatrix(Float64List matrix4, int filterQuality);

  @Native<Void Function(Pointer<Void>, Pointer<Void>)>(symbol: 'ImageFilter::initColorFilter')
  external void _initColorFilter(_ColorFilter? colorFilter);

  @Native<Void Function(Pointer<Void>, Pointer<Void>, Pointer<Void>)>(
    symbol: 'ImageFilter::initComposeFilter',
  )
  external void _initComposed(_ImageFilter outerFilter, _ImageFilter innerFilter);

  @Native<Void Function(Pointer<Void>, Pointer<Void>)>(symbol: 'ImageFilter::initShader')
  external void _initShader(FragmentShader shader);

  /// The original Dart object that created the native wrapper, which retains
  /// the values used for the filter.
  final ImageFilter creator;
}

/// Base class for objects such as [Gradient] and [ImageShader] which
/// correspond to shaders as used by [Paint.shader].
base class Shader extends NativeFieldWrapperClass1 {
  /// This class is created by the engine, and should not be instantiated
  /// or extended directly.
  @pragma('vm:entry-point')
  Shader._();

  bool _debugDisposed = false;

  /// Whether [dispose] has been called.
  ///
  /// This must only be used when asserts are enabled. Otherwise, it will throw.
  bool get debugDisposed {
    late bool disposed;
    assert(() {
      disposed = _debugDisposed;
      return true;
    }());
    return disposed;
  }

  /// Release the resources used by this object. The object is no longer usable
  /// after this method is called.
  ///
  /// The underlying memory allocated by this object will be retained beyond
  /// this call if it is still needed by another object that has not been
  /// disposed. For example, a [Picture] that has not been disposed that
  /// refers to an [ImageShader] may keep its underlying resources alive.
  ///
  /// Classes that override this method must call `super.dispose()`.
  void dispose() {
    assert(() {
      assert(!_debugDisposed, 'A Shader cannot be disposed more than once.');
      _debugDisposed = true;
      return true;
    }());
  }
}

/// Defines how to handle areas outside the defined bounds of a gradient or image filter.
///
/// ## For Gradients
///
/// Gradients are defined with some specific bounds creating an inner area and an outer area, and `TileMode` controls how colors
/// are determined for areas outside these bounds:
///
/// - **Linear gradients**: The inner area is the area between two points
///   (typically referred to as `start` and `end` in the gradient API), or more precisely,
///   it's the area between the parallel lines that are orthogonal to the line drawn between the two points.
///   Colors outside this area are determined by the `TileMode`.
///
/// - **Radial gradients**: The inner area is the disc defined by a center and radius.
///   Colors outside this disc are determined by the `TileMode`.
///
/// - **Sweep gradients**: The inner area is the angular sector between `startAngle`
///   and `endAngle`. Colors outside this sector are determined by the `TileMode`.
///
/// ## For Image Filters
///
/// When applying filters (like blur) that sample colors from outside an image's bounds,
/// `TileMode` defines how those out-of-bounds samples are determined:
///
/// - It controls what color values are used when the filter needs to sample
///   from areas outside the original image.
/// - This is particularly important for effects like blurring near image edges.
///
/// See also:
///
///  * [painting.Gradient], the superclass for [LinearGradient] and
///    [RadialGradient], as used by [BoxDecoration] et al, which works in
///    relative coordinates and can create a [Shader] representing the gradient
///    for a particular [Rect] on demand.
///  * [dart:ui.Gradient], the low-level class used when dealing with the
///    [Paint.shader] property directly, with its [Gradient.linear] and
///    [Gradient.radial] constructors.
///  * [dart:ui.ImageFilter.blur], an ImageFilter that may sometimes need to
///    read samples from outside an image to combine with the pixels near the
///    edge of the image.
// These enum values must be kept in sync with DlTileMode.
enum TileMode {
  /// Samples beyond the edge are clamped to the nearest color in the defined inner area.
  ///
  /// For gradients, this means the region outside the inner area is painted with
  /// the color at the end of the color stop list closest to that region.
  ///
  /// For sweep gradients specifically, the entire area outside the angular sector
  /// defined by [startAngle] and [endAngle] will be painted with the color at the
  /// end of the color stop list closest to that region.
  ///
  /// An image filter will substitute the nearest edge pixel for any samples taken from
  /// outside its source image.
  ///
  /// ![](https://flutter.github.io/assets-for-api-docs/assets/dart-ui/tile_mode_clamp_linear.png)
  /// ![](https://flutter.github.io/assets-for-api-docs/assets/dart-ui/tile_mode_clamp_radial.png)
  /// ![](https://flutter.github.io/assets-for-api-docs/assets/dart-ui/tile_mode_clamp_sweep.png)
  clamp,

  /// Samples beyond the edge are repeated from the far end of the defined area.
  ///
  /// For a gradient, this technique is as if the stop points from 0.0 to 1.0 were then
  /// repeated from 1.0 to 2.0, 2.0 to 3.0, and so forth (and for linear gradients, similarly
  /// from -1.0 to 0.0, -2.0 to -1.0, etc).
  ///
  /// For sweep gradients, the gradient pattern is repeated in the same direction
  /// (clockwise) for angles beyond [endAngle] and before [startAngle].
  ///
  /// An image filter will treat its source image as if it were tiled across the enlarged
  /// sample space from which it reads, each tile in the same orientation as the base image.
  ///
  /// ![](https://flutter.github.io/assets-for-api-docs/assets/dart-ui/tile_mode_repeated_linear.png)
  /// ![](https://flutter.github.io/assets-for-api-docs/assets/dart-ui/tile_mode_repeated_radial.png)
  /// ![](https://flutter.github.io/assets-for-api-docs/assets/dart-ui/tile_mode_repeated_sweep.png)
  repeated,

  /// Samples beyond the edge are mirrored back and forth across the defined area.
  ///
  /// For a gradient, this technique is as if the stop points from 0.0 to 1.0 were then
  /// repeated backwards from 2.0 to 1.0, then forwards from 2.0 to 3.0, then backwards
  /// again from 4.0 to 3.0, and so forth (and for linear gradients, similarly in the
  /// negative direction).
  ///
  /// For sweep gradients, the gradient pattern is mirrored back and forth as the angle
  /// increases beyond [endAngle] or decreases below [startAngle].
  ///
  /// An image filter will treat its source image as tiled in an alternating forwards and
  /// backwards or upwards and downwards direction across the sample space from which
  /// it is reading.
  ///
  /// ![](https://flutter.github.io/assets-for-api-docs/assets/dart-ui/tile_mode_mirror_linear.png)
  /// ![](https://flutter.github.io/assets-for-api-docs/assets/dart-ui/tile_mode_mirror_radial.png)
  /// ![](https://flutter.github.io/assets-for-api-docs/assets/dart-ui/tile_mode_mirror_sweep.png)
  mirror,

  /// Samples beyond the edge are treated as transparent black.
  ///
  /// A gradient will render transparency over any region that is outside the circle of a
  /// radial gradient, outside the parallel lines that define the inner area of a linear
  /// gradient, or outside the angular sector of a sweep gradient.
  ///
  /// For sweep gradients, only the sector between [startAngle] and [endAngle] will be
  /// painted; all other areas will be transparent.
  ///
  /// An image filter will substitute transparent black for any sample it must read from
  /// outside its source image.
  ///
  /// ![](https://flutter.github.io/assets-for-api-docs/assets/dart-ui/tile_mode_decal_linear.png)
  /// ![](https://flutter.github.io/assets-for-api-docs/assets/dart-ui/tile_mode_decal_radial.png)
  /// ![](https://flutter.github.io/assets-for-api-docs/assets/dart-ui/tile_mode_decal_sweep.png)
  decal,
}

Float32List _encodeWideColorList(List<Color> colors) {
  final int colorCount = colors.length;
  final result = Float32List(colorCount * 4);
  for (var i = 0; i < colorCount; i++) {
    final Color colorXr = colors[i].withValues(colorSpace: ColorSpace.extendedSRGB);
    result[i * 4 + 0] = colorXr.a;
    result[i * 4 + 1] = colorXr.r;
    result[i * 4 + 2] = colorXr.g;
    result[i * 4 + 3] = colorXr.b;
  }
  return result;
}

Int32List _encodeColorList(List<Color> colors) {
  final int colorCount = colors.length;
  final result = Int32List(colorCount);
  for (var i = 0; i < colorCount; i++) {
    result[i] = colors[i].value;
  }
  return result;
}

Float32List _encodePointList(List<Offset> points) {
  final int pointCount = points.length;
  final result = Float32List(pointCount * 2);
  for (var i = 0; i < pointCount; i++) {
    final int xIndex = i * 2;
    final int yIndex = xIndex + 1;
    final Offset point = points[i];
    assert(_offsetIsValid(point));
    result[xIndex] = point.dx;
    result[yIndex] = point.dy;
  }
  return result;
}

Float32List _encodeTwoPoints(Offset pointA, Offset pointB) {
  assert(_offsetIsValid(pointA));
  assert(_offsetIsValid(pointB));
  final result = Float32List(4);
  result[0] = pointA.dx;
  result[1] = pointA.dy;
  result[2] = pointB.dx;
  result[3] = pointB.dy;
  return result;
}

/// A shader (as used by [Paint.shader]) that renders a color gradient.
///
/// There are several types of gradients, represented by the various constructors
/// on this class.
///
/// See also:
///
///  * [Gradient](https://api.flutter.dev/flutter/painting/Gradient-class.html), the class in the [painting] library.
///
base class Gradient extends Shader {
  /// Creates a linear gradient from `from` to `to`.
  ///
  /// If `colorStops` is provided, `colorStops[i]` is a number from 0.0 to 1.0
  /// that specifies where `color[i]` begins in the gradient. If `colorStops` is
  /// not provided, then only two stops, at 0.0 and 1.0, are implied (and
  /// `color` must therefore only have two entries). Stop values less than 0.0
  /// will be rounded up to 0.0 and stop values greater than 1.0 will be rounded
  /// down to 1.0. Each stop value must be greater than or equal to the previous
  /// stop value. Stop values that do not meet this criteria will be rounded up
  /// to the previous stop value.
  ///
  /// The behavior before `from` and after `to` is described by the `tileMode`
  /// argument. For details, see the [TileMode] enum.
  ///
  /// ![](https://flutter.github.io/assets-for-api-docs/assets/dart-ui/tile_mode_clamp_linear.png)
  /// ![](https://flutter.github.io/assets-for-api-docs/assets/dart-ui/tile_mode_decal_linear.png)
  /// ![](https://flutter.github.io/assets-for-api-docs/assets/dart-ui/tile_mode_mirror_linear.png)
  /// ![](https://flutter.github.io/assets-for-api-docs/assets/dart-ui/tile_mode_repeated_linear.png)
  ///
  /// If `from`, `to`, `colors`, or `tileMode` are null, or if `colors` or
  /// `colorStops` contain null values, this constructor will throw a
  /// [NoSuchMethodError].
  ///
  /// If `matrix4` is provided, the gradient fill will be transformed by the
  /// specified 4x4 matrix relative to the local coordinate system. `matrix4` must
  /// be a column-major matrix packed into a list of 16 values.
  Gradient.linear(
    Offset from,
    Offset to,
    List<Color> colors, [
    List<double>? colorStops,
    TileMode tileMode = TileMode.clamp,
    Float64List? matrix4,
  ]) : assert(_offsetIsValid(from)),
       assert(_offsetIsValid(to)),
       assert(matrix4 == null || _matrix4IsValid(matrix4)),
       super._() {
    _validateColorStops(colors, colorStops);
    final Float32List endPointsBuffer = _encodeTwoPoints(from, to);
    final Float32List colorsBuffer = _encodeWideColorList(colors);
    final Float32List? colorStopsBuffer = colorStops == null
        ? null
        : Float32List.fromList(colorStops);
    _constructor();
    _initLinear(endPointsBuffer, colorsBuffer, colorStopsBuffer, tileMode.index, matrix4);
  }

  /// Creates a radial gradient centered at `center` that ends at `radius`
  /// distance from the center.
  ///
  /// If `colorStops` is provided, `colorStops[i]` is a number from 0.0 to 1.0
  /// that specifies where `color[i]` begins in the gradient. If `colorStops` is
  /// not provided, then only two stops, at 0.0 and 1.0, are implied (and
  /// `color` must therefore only have two entries). Stop values less than 0.0
  /// will be rounded up to 0.0 and stop values greater than 1.0 will be rounded
  /// down to 1.0. Each stop value must be greater than or equal to the previous
  /// stop value. Stop values that do not meet this criteria will be rounded up
  /// to the previous stop value.
  ///
  /// The behavior before and after the radius is described by the `tileMode`
  /// argument. For details, see the [TileMode] enum.
  ///
  /// ![](https://flutter.github.io/assets-for-api-docs/assets/dart-ui/tile_mode_clamp_radial.png)
  /// ![](https://flutter.github.io/assets-for-api-docs/assets/dart-ui/tile_mode_decal_radial.png)
  /// ![](https://flutter.github.io/assets-for-api-docs/assets/dart-ui/tile_mode_mirror_radial.png)
  /// ![](https://flutter.github.io/assets-for-api-docs/assets/dart-ui/tile_mode_repeated_radial.png)
  ///
  /// If `center`, `radius`, `colors`, or `tileMode` are null, or if `colors` or
  /// `colorStops` contain null values, this constructor will throw a
  /// [NoSuchMethodError].
  ///
  /// If `matrix4` is provided, the gradient fill will be transformed by the
  /// specified 4x4 matrix relative to the local coordinate system. `matrix4` must
  /// be a column-major matrix packed into a list of 16 values.
  ///
  /// If `focal` is provided and not equal to `center` and `focalRadius` is
  /// provided and not equal to 0.0, the generated shader will be a two point
  /// conical radial gradient, with `focal` being the center of the focal
  /// circle and `focalRadius` being the radius of that circle. If `focal` is
  /// provided and not equal to `center`, at least one of the two offsets must
  /// not be equal to [Offset.zero].
  Gradient.radial(
    Offset center,
    double radius,
    List<Color> colors, [
    List<double>? colorStops,
    TileMode tileMode = TileMode.clamp,
    Float64List? matrix4,
    Offset? focal,
    double focalRadius = 0.0,
  ]) : assert(_offsetIsValid(center)),
       assert(matrix4 == null || _matrix4IsValid(matrix4)),
       super._() {
    _validateColorStops(colors, colorStops);
    final Float32List? colorStopsBuffer = colorStops == null
        ? null
        : Float32List.fromList(colorStops);
    final Float32List colorsBuffer = _encodeWideColorList(colors);

    // If focal is null or focal radius is null, this should be treated as a regular radial gradient
    // If focal == center and the focal radius is 0.0, it's still a regular radial gradient
    if (focal == null || (focal == center && focalRadius == 0.0)) {
      _constructor();
      _initRadial(
        center.dx,
        center.dy,
        radius,
        colorsBuffer,
        colorStopsBuffer,
        tileMode.index,
        matrix4,
      );
    } else {
      assert(
        center != Offset.zero || focal != Offset.zero,
      ); // will result in exception(s) in Skia side
      _constructor();
      _initConical(
        focal.dx,
        focal.dy,
        focalRadius,
        center.dx,
        center.dy,
        radius,
        colorsBuffer,
        colorStopsBuffer,
        tileMode.index,
        matrix4,
      );
    }
  }

  /// Creates a sweep gradient centered at `center` that starts at `startAngle`
  /// and ends at `endAngle`.
  ///
  /// `startAngle` and `endAngle` should be provided in radians, with zero
  /// radians being the horizontal line to the right of the `center` and with
  /// positive angles going clockwise around the `center`.
  ///
  /// If `colorStops` is provided, `colorStops[i]` is a number from 0.0 to 1.0
  /// that specifies where `colors[i]` begins in the gradient. If `colorStops` is
  /// not provided, then only two stops, at 0.0 and 1.0, are implied
  /// (and `colors` must therefore only have two entries). Stop values less than
  /// 0.0 will be rounded up to 0.0 and stop values greater than 1.0 will be
  /// rounded down to 1.0. Each stop value must be greater than or equal to the
  /// previous stop value. Stop values that do not meet this criteria will be
  /// rounded up to the previous stop value.
  ///
  /// The `startAngle` and `endAngle` parameters define the angular sector to be
  /// painted. Angles are measured in radians clockwise from the positive x-axis.
  /// Values outside the range `[0, 2π]` are normalized to this range using modulo
  /// arithmetic. The gradient is only painted in the sector between `startAngle`
  /// and `endAngle`. The `tileMode` determines how the gradient behaves outside
  /// this sector.
  ///
  /// The `tileMode` argument specifies how the gradient should handle areas
  /// outside the angular sector defined by `startAngle` and `endAngle`:
  ///
  /// The behavior before `startAngle` and after `endAngle` is described by the
  /// `tileMode` argument. For details, see the [TileMode] enum.
  ///
  /// * [TileMode.clamp]: The edge colors are extended to infinity.
  /// * [TileMode.mirror]: The gradient is repeated, alternating direction each time.
  /// * [TileMode.repeated]: The gradient is repeated in the same direction.
  /// * [TileMode.decal]: Only the colors within the gradient's angular sector are
  ///   drawn, with transparent black elsewhere.
  ///
  /// The [colorStops] argument must have the same number of values as [colors],
  /// if specified. It specifies the position of each color stop between 0.0 and
  /// 1.0. If it is null, a uniform distribution is assumed. The stop values must
  /// be in ascending order. A stop value of 0.0 corresponds to [startAngle], and
  /// a stop value of 1.0 corresponds to [endAngle].
  ///
  /// ![](https://flutter.github.io/assets-for-api-docs/assets/dart-ui/tile_mode_clamp_sweep.png)
  /// ![](https://flutter.github.io/assets-for-api-docs/assets/dart-ui/tile_mode_decal_sweep.png)
  /// ![](https://flutter.github.io/assets-for-api-docs/assets/dart-ui/tile_mode_mirror_sweep.png)
  /// ![](https://flutter.github.io/assets-for-api-docs/assets/dart-ui/tile_mode_repeated_sweep.png)
  ///
  /// If `center`, `colors`, `tileMode`, `startAngle`, or `endAngle` are null,
  /// or if `colors` or `colorStops` contain null values, this constructor will
  /// throw a [NoSuchMethodError].
  ///
  /// If `matrix4` is provided, the gradient fill will be transformed by the
  /// specified 4x4 matrix relative to the local coordinate system. `matrix4` must
  /// be a column-major matrix packed into a list of 16 values.
  Gradient.sweep(
    Offset center,
    List<Color> colors, [
    List<double>? colorStops,
    TileMode tileMode = TileMode.clamp,
    double startAngle = 0.0,
    double endAngle = math.pi * 2,
    Float64List? matrix4,
  ]) : assert(_offsetIsValid(center)),
       assert(startAngle < endAngle),
       assert(matrix4 == null || _matrix4IsValid(matrix4)),
       super._() {
    _validateColorStops(colors, colorStops);
    final Float32List colorsBuffer = _encodeWideColorList(colors);
    final Float32List? colorStopsBuffer = colorStops == null
        ? null
        : Float32List.fromList(colorStops);
    _constructor();
    _initSweep(
      center.dx,
      center.dy,
      colorsBuffer,
      colorStopsBuffer,
      tileMode.index,
      startAngle,
      endAngle,
      matrix4,
    );
  }

  @Native<Void Function(Handle)>(symbol: 'Gradient::Create')
  external void _constructor();

  @Native<Void Function(Pointer<Void>, Handle, Handle, Handle, Int32, Handle)>(
    symbol: 'Gradient::initLinear',
  )
  external void _initLinear(
    Float32List endPoints,
    Float32List colors,
    Float32List? colorStops,
    int tileMode,
    Float64List? matrix4,
  );

  @Native<Void Function(Pointer<Void>, Double, Double, Double, Handle, Handle, Int32, Handle)>(
    symbol: 'Gradient::initRadial',
  )
  external void _initRadial(
    double centerX,
    double centerY,
    double radius,
    Float32List colors,
    Float32List? colorStops,
    int tileMode,
    Float64List? matrix4,
  );

  @Native<
    Void Function(
      Pointer<Void>,
      Double,
      Double,
      Double,
      Double,
      Double,
      Double,
      Handle,
      Handle,
      Int32,
      Handle,
    )
  >(symbol: 'Gradient::initTwoPointConical')
  external void _initConical(
    double startX,
    double startY,
    double startRadius,
    double endX,
    double endY,
    double endRadius,
    Float32List colors,
    Float32List? colorStops,
    int tileMode,
    Float64List? matrix4,
  );

  @Native<
    Void Function(Pointer<Void>, Double, Double, Handle, Handle, Int32, Double, Double, Handle)
  >(symbol: 'Gradient::initSweep')
  external void _initSweep(
    double centerX,
    double centerY,
    Float32List colors,
    Float32List? colorStops,
    int tileMode,
    double startAngle,
    double endAngle,
    Float64List? matrix,
  );

  static void _validateColorStops(List<Color> colors, List<double>? colorStops) {
    if (colorStops == null) {
      if (colors.length != 2) {
        throw ArgumentError('"colors" must have length 2 if "colorStops" is omitted.');
      }
    } else {
      if (colors.length != colorStops.length) {
        throw ArgumentError('"colors" and "colorStops" arguments must have equal length.');
      }
    }
  }
}

/// A shader (as used by [Paint.shader]) that tiles an image.
base class ImageShader extends Shader {
  /// Creates an image-tiling shader.
  ///
  /// The first argument specifies the image to render. The
  /// [decodeImageFromList] function can be used to decode an image from bytes
  /// into the form expected here. (In production code, starting from
  /// [instantiateImageCodec] may be preferable.)
  ///
  /// The second and third arguments specify the [TileMode] for the x direction
  /// and y direction respectively. [TileMode.repeated] can be used for tiling
  /// images.
  ///
  /// The fourth argument gives the matrix to apply to the effect. The
  /// expression `Matrix4.identity().storage` creates a [Float64List]
  /// prepopulated with the identity matrix.
  ///
  /// All the arguments are required and must not be null, except for
  /// [filterQuality]. If [filterQuality] is not specified at construction time
  /// it will be deduced from the environment where it is used, such as from
  /// [Paint.filterQuality].
  @pragma('vm:entry-point')
  ImageShader(
    Image image,
    TileMode tmx,
    TileMode tmy,
    Float64List matrix4, {
    FilterQuality? filterQuality,
  }) : assert(!image.debugDisposed),
       super._() {
    if (matrix4.length != 16) {
      throw ArgumentError('"matrix4" must have 16 entries.');
    }
    _constructor();
    final String? error = _initWithImage(
      image._image,
      tmx.index,
      tmy.index,
      filterQuality?.index ?? -1,
      matrix4,
    );
    if (error != null) {
      throw Exception(error);
    }
  }

  @override
  void dispose() {
    super.dispose();
    _dispose();
  }

  @Native<Void Function(Handle)>(symbol: 'ImageShader::Create')
  external void _constructor();

  @Native<Handle Function(Pointer<Void>, Pointer<Void>, Int32, Int32, Int32, Handle)>(
    symbol: 'ImageShader::initWithImage',
  )
  external String? _initWithImage(
    _Image image,
    int tmx,
    int tmy,
    int filterQualityIndex,
    Float64List matrix4,
  );

  /// This can't be a leaf call because the native function calls Dart API
  /// (Dart_SetNativeInstanceField).
  @Native<Void Function(Pointer<Void>)>(symbol: 'ImageShader::dispose')
  external void _dispose();
}

typedef _UniformFloatInfo = ({int index, int size});

/// An instance of [FragmentProgram] creates [Shader] objects (as used by
/// [Paint.shader]).
///
/// For more information, see the website
/// [documentation]( https://docs.flutter.dev/development/ui/advanced/shaders).
base class FragmentProgram extends NativeFieldWrapperClass1 {
  @pragma('vm:entry-point')
  FragmentProgram._fromAsset(String assetKey) {
    _constructor();
    final String result = _initFromAsset(assetKey);
    if (result.isNotEmpty) {
      throw Exception(result);
    }
    assert(() {
      _debugName = assetKey;
      return true;
    }());
  }

  String? _debugName;
  final List<WeakReference<FragmentShader>> _shaders = <WeakReference<FragmentShader>>[];

  /// Creates a fragment program from the asset with key [assetKey].
  ///
  /// The asset must be a file produced as the output of the `impellerc`
  /// compiler. The constructed object should then be reused via the
  /// [fragmentShader] method to create [Shader] objects that can be used by
  /// [Paint.shader].
  static Future<FragmentProgram> fromAsset(String assetKey) {
    // The flutter tool converts all asset keys with spaces into URI
    // encoded paths (replacing ' ' with '%20', for example). We perform
    // the same encoding here so that users can load assets with the same
    // key they have written in the pubspec.
    final String encodedKey = Uri(path: Uri.encodeFull(assetKey)).path;
    final FragmentProgram? program = _shaderRegistry[encodedKey];
    if (program != null) {
      return Future<FragmentProgram>.value(program);
    }
    return Future<FragmentProgram>.microtask(() {
      final program = FragmentProgram._fromAsset(encodedKey);
      _shaderRegistry[encodedKey] = program;
      return program;
    });
  }

  // This is a cache of shaders that have been loaded by
  // FragmentProgram.fromAsset. It holds a strong reference to theFragmentPrograms
  // The native engine will retain the resources associated with this shader
  // program (PSO variants) until shutdown, so maintaining a strong reference
  // here ensures we do not perform extra work if the dart object is continually
  // re-initialized.
  static final Map<String, FragmentProgram> _shaderRegistry = <String, FragmentProgram>{};

  // This is called on hot reload when a shader has changed.
  static void _reinitializeShader(String assetKey) {
    // If a shader for the asset isn't already registered, then there's no
    // need to reinitialize it. The new shader will be loaded and initialized
    // the next time the program access it.
    final FragmentProgram? program = _shaderRegistry[assetKey];
    if (program == null) {
      return;
    }

    final String result = program._initFromAsset(assetKey);
    if (result.isNotEmpty) {
      throw result; // ignore: only_throw_errors
    }

    // Update all the named bindings.
    program._shaders.removeWhere((WeakReference<FragmentShader> shaderReference) {
      final FragmentShader? shader = shaderReference.target;
      if (shader == null) {
        return true;
      }

      shader._reinitialize();
      shader._slots.removeWhere((WeakReference<UniformFloatSlot> slotReference) {
        final UniformFloatSlot? slot = slotReference.target;
        if (slot == null) {
          return true;
        }

        if (!program._hasUniform(slot.name)) {
          return true;
        }

        final _UniformFloatInfo info = program._getUniformFloatInfo(slot.name);
        slot._shaderIndex = info.index + slot.index;

        return false;
      });

      shader._samplers.removeWhere((WeakReference<ImageSamplerSlot> ref) {
        final ImageSamplerSlot? slot = ref.target;
        if (slot == null) {
          return true;
        }

        slot._shaderIndex = program._getImageSamplerIndex(slot.name);
        return false;
      });

      return false;
    });
  }

  bool _hasUniform(String name) {
    return _uniformInfo.any((dynamic entryDynamic) {
      final entry = entryDynamic! as Map<String, Object>;
      return entry['name'] == name ||
          (entry['type'] == 'Struct' &&
              (entry['struct_field_names']! as List<dynamic>).contains(name));
    });
  }

  int _getImageSamplerIndex(String name) {
    var index = 0;
    var found = false;
    for (final Object? entryDynamic in _uniformInfo) {
      final entry = entryDynamic! as Map<String, Object>;
      if (entry['name'] == name) {
        if (entry['type'] != 'SampledImage') {
          throw ArgumentError('Uniform "$name" is not an image sampler.');
        }
        found = true;
        break;
      } else if (entry['type'] == 'SampledImage') {
        index += 1;
      }
    }

    if (!found) {
      if (_hasUniform(name)) {
        throw ArgumentError('Uniform "$name" is not an image sampler.');
      } else {
        throw ArgumentError('No uniform named "$name".');
      }
    }
    return index;
  }

  _UniformFloatInfo _getUniformFloatInfo(String name) {
    var offset = 0;
    var sizeInFloats = 0;
    var found = false;
    const sizeOfFloat = 4;
    for (final Object? entryDynamic in _uniformInfo) {
      final entry = entryDynamic! as Map<String, Object>;
      if (found) {
        break;
      }

      if (entry['type'] == 'Struct') {
        final elementNames = entry['struct_field_names']! as List<dynamic>;
        final elementSizes = entry['struct_field_bytes']! as List<dynamic>;

        for (var i = 0; i < elementNames.length; ++i) {
          final elementName = elementNames[i]! as String;
          final elementSize = elementSizes[i]! as int;
          sizeInFloats = elementSize ~/ sizeOfFloat;
          if (elementName == name) {
            found = true;
            break;
          }
          offset += sizeInFloats;
        }
      } else {
        sizeInFloats = (entry['size'] as int? ?? 0) ~/ sizeOfFloat;
        if (entry['name'] == name) {
          found = true;
          break;
        }
        offset += sizeInFloats;
      }
    }

    if (!found) {
      throw ArgumentError('No uniform named "$name".');
    }

    return (index: offset, size: sizeInFloats);
  }

  @pragma('vm:entry-point')
  late int _uniformFloatCount;

  @pragma('vm:entry-point')
  late int _samplerCount;

  @pragma('vm:entry-point')
  late List<dynamic> _uniformInfo;

  @Native<Void Function(Handle)>(symbol: 'FragmentProgram::Create')
  external void _constructor();

  @Native<Handle Function(Pointer<Void>, Handle)>(symbol: 'FragmentProgram::initFromAsset')
  external String _initFromAsset(String assetKey);

  /// Returns a fresh instance of [FragmentShader].
  FragmentShader fragmentShader() {
    final result = FragmentShader._(this, debugName: _debugName);
    _shaders.removeWhere((WeakReference<FragmentShader> ref) => ref.target == null);
    _shaders.add(WeakReference<FragmentShader>(result));
    return result;
  }
}

/// A binding into a uniform defined in a shader. Used now to restrict the types
/// of UniformArrays that can be created.
sealed class UniformType {}

/// A binding to a uniform of type float. Calling [set] on this object updates
/// a float uniform's value.
///
/// Example:
///
/// ```dart
/// void updateShader(ui.FragmentShader shader) {
///   shader.getUniformFloat('uColor', 0).set(1.0);
///   shader.getUniformFloat('uColor', 1).set(0.0);
///   shader.getUniformFloat('uColor', 2).set(0.0);
/// }
/// ```
///
/// See also:
///   [FragmentShader.getUniformFloat] - How [UniformFloatSlot] instances are acquired.
///
base class UniformFloatSlot extends UniformType {
  UniformFloatSlot._(this._shader, this.name, this.index, this._shaderIndex);

  /// Set the float value of the bound uniform.
  void set(double val) {
    _shader.setFloat(_shaderIndex, val);
  }

  /// VisibleForTesting: This is the index one would use with
  /// [FragmentShader.setFloat] for this uniform.
  int get shaderIndex {
    return _shaderIndex;
  }

  final FragmentShader _shader;
  int _shaderIndex;

  /// The name of the bound uniform.
  final String name;

  /// The offset into the bound uniform. For example, 1 for `.y` or 2 for `.b`.
  final int index;
}

/// A binding to a uniform of type vec2. Calling [set] on this object updates
/// the uniform's value.
///
/// Example:
///
/// ```dart
/// void updateShader(ui.FragmentShader shader) {
///   shader.getUniformVec2('uSize').set(100, 100);
/// }
/// ```
///
/// See also:
///   [FragmentShader.getUniformVec2] - How [UniformVec2Slot] instances are acquired.
///
base class UniformVec2Slot extends UniformType {
  UniformVec2Slot._(this._xSlot, this._ySlot);

  /// Set the float value of the bound uniform.
  void set(double x, double y) {
    _xSlot.set(x);
    _ySlot.set(y);
  }

  final UniformFloatSlot _xSlot, _ySlot;
}

/// A binding to a uniform of type vec3. Calling [set] on this object updates
/// the uniform's value.
///
/// Example:
///
/// ```dart
/// void updateShader(ui.FragmentShader shader, double time) {
///   shader.getUniformVec3('uScaledTime').set(time, time*0.1, time*0.01);
/// }
/// ```
///
/// See also:
///   [FragmentShader.getUniformVec3] - How [UniformVec3Slot] instances are acquired.
///
base class UniformVec3Slot extends UniformType {
  UniformVec3Slot._(this._xSlot, this._ySlot, this._zSlot);

  /// Set the float value of the bound uniform.
  void set(double x, double y, double z) {
    _xSlot.set(x);
    _ySlot.set(y);
    _zSlot.set(z);
  }

  final UniformFloatSlot _xSlot, _ySlot, _zSlot;
}

/// A binding to a uniform of type vec4. Calling [set] on this object updates
/// the uniform's value.
///
/// Example:
///
/// ```dart
/// void updateShader(ui.FragmentShader shader) {
///   shader.getUniformVec4('uColor').set(1.0, 0.0, 1.0, 1.0);
/// }
/// ```
///
/// See also:
///   [FragmentShader.getUniformVec4] - How [UniformVec4Slot] instances are acquired.
///
base class UniformVec4Slot extends UniformType {
  UniformVec4Slot._(this._xSlot, this._ySlot, this._zSlot, this._wSlot);

  /// Set the float value of the bound uniform.
  void set(double x, double y, double z, double w) {
    _xSlot.set(x);
    _ySlot.set(y);
    _zSlot.set(z);
    _wSlot.set(w);
  }

  final UniformFloatSlot _xSlot, _ySlot, _zSlot, _wSlot;
}

/// A binding to a uniform of type mat2. Calling [set] on this object updates
/// the uniform's value.
///
/// Example:
///
/// ```dart
/// void updateShader(ui.FragmentShader shader) {
///   shader.getUniformMat2('uIdentity').set(
///     1.0, 0.0,
///     0.0, 1.0
///   );
/// }
/// ```
///
/// See also:
///   [FragmentShader.getUniformMat2] - How [UniformMat2Slot] instances are acquired.
///
base class UniformMat2Slot extends UniformType {
  UniformMat2Slot._(this._m00, this._m01, this._m10, this._m11);

  /// Set the float value of the matrix in row-major order.
  void set(double m00, double m01, double m10, double m11) {
    _m00.set(m00);
    _m01.set(m01);
    _m10.set(m10);
    _m11.set(m11);
  }

  final UniformFloatSlot _m00, _m01, _m10, _m11;
}

/// A binding to a uniform of type mat3. Calling [set] on this object updates
/// the uniform's value.
///
/// Example:
///
/// ```dart
/// void updateShader(ui.FragmentShader shader) {
///   shader.getUniformMat3('uIdentity').set(
///     1.0, 0.0, 0.0,
///     0.0, 1.0, 0.0,
///     0.0, 0.0, 1.0
///   );
/// }
/// ```
///
/// See also:
///   [FragmentShader.getUniformMat3] - How [UniformMat3Slot] instances are acquired.
///
base class UniformMat3Slot extends UniformType {
  UniformMat3Slot._(
    this._m00,
    this._m01,
    this._m02,
    this._m10,
    this._m11,
    this._m12,
    this._m20,
    this._m21,
    this._m22,
  );

  /// Set the float value of the matrix in row-major order.
  void set(
    double m00,
    double m01,
    double m02,
    double m10,
    double m11,
    double m12,
    double m20,
    double m21,
    double m22,
  ) {
    _m00.set(m00);
    _m01.set(m01);
    _m02.set(m02);
    _m10.set(m10);
    _m11.set(m11);
    _m12.set(m12);
    _m20.set(m20);
    _m21.set(m21);
    _m22.set(m22);
  }

  final UniformFloatSlot _m00, _m01, _m02, _m10, _m11, _m12, _m20, _m21, _m22;
}

/// A binding to a uniform of type mat4. Calling [set] on this object updates
/// the uniform's value.
///
/// Example:
///
/// ```dart
/// void updateShader(ui.FragmentShader shader) {
///   shader.getUniformMat4('uIdentity').set(
///     1.0, 0.0, 0.0, 0.0,
///     0.0, 1.0, 0.0, 0.0,
///     0.0, 0.0, 1.0, 0.0,
///     0.0, 0.0, 0.0, 1.0
///   );
/// }
/// ```
///
/// See also:
///   [FragmentShader.getUniformMat4] - How [UniformMat4Slot] instances are acquired.
///

base class UniformMat4Slot extends UniformType {
  UniformMat4Slot._(
    this._m00,
    this._m01,
    this._m02,
    this._m03,
    this._m10,
    this._m11,
    this._m12,
    this._m13,
    this._m20,
    this._m21,
    this._m22,
    this._m23,
    this._m30,
    this._m31,
    this._m32,
    this._m33,
  );

  /// Set the float value of the matrix in row-major order.
  void set(
    double m00,
    double m01,
    double m02,
    double m03,
    double m10,
    double m11,
    double m12,
    double m13,
    double m20,
    double m21,
    double m22,
    double m23,
    double m30,
    double m31,
    double m32,
    double m33,
  ) {
    _m00.set(m00);
    _m01.set(m01);
    _m02.set(m02);
    _m03.set(m03);
    _m10.set(m10);
    _m11.set(m11);
    _m12.set(m12);
    _m13.set(m13);
    _m20.set(m20);
    _m21.set(m21);
    _m22.set(m22);
    _m23.set(m23);
    _m30.set(m30);
    _m31.set(m31);
    _m32.set(m32);
    _m33.set(m33);
  }

  final UniformFloatSlot _m00,
      _m01,
      _m02,
      _m03,
      _m10,
      _m11,
      _m12,
      _m13,
      _m20,
      _m21,
      _m22,
      _m23,
      _m30,
      _m31,
      _m32,
      _m33;
}

/// An array of bindings to uniforms of the same type T. Access elements via [] and
/// set them individually.
/// Example:
///
/// ```dart
/// void updateShader(ui.FragmentShader shader) {
///   final ui.UniformArray<ui.UniformVec4Slot> colors = shader.getUniformVec4Array('uColorArray');
///   colors[0].set(1.0, 0.0, 1.0, 0.3);
/// }
/// ```
///
/// See also:
///   [FragmentShader.getUniformFloatArray] - How [UniformArray<Float>] instances are acquired.
///
class UniformArray<T extends UniformType> {
  UniformArray._(this._elements);

  /// Access an element of the UniformArray.
  T operator [](int index) {
    return _elements[index];
  }

  /// The number of Uniforms in the UniformArray.
  int get length => _elements.length;

  final List<T> _elements;
}

/// A binding to a shader's image sampler. Calling [set] on this object updates
/// a sampler's bound image.
base class ImageSamplerSlot {
  ImageSamplerSlot._(this._shader, this.name, this._shaderIndex);

  final FragmentShader _shader;
  int _shaderIndex;

  /// Set the [Image] value for the bound sampler associated with this slot.
  void set(Image val) {
    _shader.setImageSampler(_shaderIndex, val);
  }

  /// VisibleForTesting: This is the index one would use with
  /// [FragmentShader.setImageSampler] for this sampler.
  int get shaderIndex => _shaderIndex;

  /// The name of the bound uniform.
  final String name;
}

/// A [Shader] generated from a [FragmentProgram].
///
/// Instances of this class can be obtained from the
/// [FragmentProgram.fragmentShader] method. The float uniforms list is
/// initialized to the size expected by the shader and is zero-filled. Uniforms
/// of float type can then be set by calling [setFloat]. Sampler uniforms are
/// set by calling [setImageSampler].
///
/// A [FragmentShader] can be re-used, and this is an efficient way to avoid
/// allocating and re-initializing the uniform buffer and samplers. However,
/// if two [FragmentShader] objects with different float uniforms or samplers
/// are required to exist simultaneously, they must be obtained from two
/// different calls to [FragmentProgram.fragmentShader].
base class FragmentShader extends Shader {
  FragmentShader._(this._program, {String? debugName}) : _debugName = debugName, super._() {
    _floats = _constructor(_program, _program._uniformFloatCount, _program._samplerCount);
  }

  final FragmentProgram _program;

  final String? _debugName;

  static final Float32List _kEmptyFloat32List = Float32List(0);
  Float32List _floats = _kEmptyFloat32List;
  final List<WeakReference<UniformFloatSlot>> _slots = <WeakReference<UniformFloatSlot>>[];
  final List<WeakReference<ImageSamplerSlot>> _samplers = <WeakReference<ImageSamplerSlot>>[];

  void _reinitialize() {
    _floats = _constructor(_program, _program._uniformFloatCount, _program._samplerCount);
  }

  List<UniformFloatSlot> _getSlotsForUniform(String name, int size) {
    final _UniformFloatInfo info = _program._getUniformFloatInfo(name);

    if (info.size != size) {
      throw ArgumentError('Uniform `$name` has size ${info.size}, not size $size.');
    }

    final slots = List<UniformFloatSlot>.generate(
      size,
      (i) => UniformFloatSlot._(this, name, i, info.index + i),
    );
    _slots.removeWhere((WeakReference<UniformFloatSlot> ref) => ref.target == null);
    _slots.addAll(slots.map((slot) => WeakReference<UniformFloatSlot>(slot)));
    return slots;
  }

  /// Sets the float uniform at [index] to [value].
  ///
  /// All uniforms defined in a fragment shader that are not samplers must be
  /// set through this method. This includes floats and vec2, vec3, and vec4.
  /// The correct index for each uniform is determined by the order of the
  /// uniforms as defined in the fragment program, ignoring any samplers. For
  /// data types that are composed of multiple floats such as a vec4, more than
  /// one call to [setFloat] is required.
  ///
  /// For example, given the following uniforms in a fragment program:
  ///
  /// ```glsl
  /// uniform float uScale;
  /// uniform sampler2D uTexture;
  /// uniform vec2 uMagnitude;
  /// uniform vec4 uColor;
  /// ```
  ///
  /// Then the corresponding Dart code to correctly initialize these uniforms
  /// is:
  ///
  /// ```dart
  /// void updateShader(ui.FragmentShader shader, Color color, ui.Image image) {
  ///   shader.setFloat(0, 23);  // uScale
  ///   shader.setFloat(1, 114); // uMagnitude x
  ///   shader.setFloat(2, 83);  // uMagnitude y
  ///
  ///   // Convert color to premultiplied opacity.
  ///   shader.setFloat(3, color.r * color.a); // uColor r
  ///   shader.setFloat(4, color.g * color.a); // uColor g
  ///   shader.setFloat(5, color.b * color.a); // uColor b
  ///   shader.setFloat(6, color.a);           // uColor a
  ///
  ///   // initialize sampler uniform.
  ///   shader.setImageSampler(0, image);
  /// }
  /// ```
  ///
  /// Note how the indexes used does not count the `sampler2D` uniform. This
  /// uniform will be set separately with [setImageSampler], with the index starting
  /// over at 0.
  ///
  /// Any float uniforms that are left uninitialized will default to `0`.
  void setFloat(int index, double value) {
    assert(!debugDisposed, 'Tried to accesss uniforms on a disposed Shader: $this');
    _floats[index] = value;
  }

  /// Access the float binding for uniform named [name] with optional offset
  /// [index]. Example [index] values: 1 for 'foo.y', 2 for 'foo.b'.
  ///
  /// Example:
  ///
  /// ```glsl
  /// uniform float uScale;
  /// uniform sampler2D uTexture;
  /// uniform vec2 uMagnitude;
  /// uniform vec4 uColor;
  /// ```
  ///
  /// ```dart
  /// void updateShader(ui.FragmentShader shader) {
  ///   shader.getUniformFloat('uScale');
  ///   shader.getUniformFloat('uMagnitude', 0);
  ///   shader.getUniformFloat('uMagnitude', 1);
  ///   shader.getUniformFloat('uColor', 0);
  ///   shader.getUniformFloat('uColor', 1);
  ///   shader.getUniformFloat('uColor', 2);
  ///   shader.getUniformFloat('uColor', 3);
  /// }
  /// ```
  UniformFloatSlot getUniformFloat(String name, [int? index]) {
    index ??= 0;

    final _UniformFloatInfo info = _program._getUniformFloatInfo(name);

    IndexError.check(index, info.size, message: 'Index `$index` out of bounds for `$name`.');

    final result = UniformFloatSlot._(this, name, index, info.index + index);
    _slots.removeWhere((WeakReference<UniformFloatSlot> ref) => ref.target == null);
    _slots.add(WeakReference<UniformFloatSlot>(result));
    return result;
  }

  /// Access the float binding for a vec2 uniform named [name].
  ///
  /// Example:
  ///
  /// ```glsl
  /// uniform float uScale;
  /// uniform vec2 uMagnitude;
  /// ```
  ///
  /// ```dart
  /// void updateShader(ui.FragmentShader shader) {
  ///   shader.getUniformFloat('uScale');
  ///   shader.getUniformVec2('uMagnitude');
  /// }
  /// ```
  UniformVec2Slot getUniformVec2(String name) {
    final List<UniformFloatSlot> slots = _getSlotsForUniform(name, 2);
    return UniformVec2Slot._(slots[0], slots[1]);
  }

  /// Access the float binding for a vec3 uniform named [name].
  ///
  /// Example:
  ///
  /// ```glsl
  /// uniform float uScale;
  /// uniform vec3 uScaledTime;
  /// ```
  ///
  /// ```dart
  /// void updateShader(ui.FragmentShader shader) {
  ///   shader.getUniformFloat('uScale');
  ///   shader.getUniformVec3('uScaledTime');
  /// }
  /// ```
  UniformVec3Slot getUniformVec3(String name) {
    final List<UniformFloatSlot> slots = _getSlotsForUniform(name, 3);
    return UniformVec3Slot._(slots[0], slots[1], slots[2]);
  }

  /// Access the float binding for a vec4 uniform named [name].
  ///
  /// Example:
  ///
  /// ```glsl
  /// uniform float uScale;
  /// uniform vec4 uColor;
  /// ```
  ///
  /// ```dart
  /// void updateShader(ui.FragmentShader shader) {
  ///   shader.getUniformFloat('uScale');
  ///   shader.getUniformVec4('uColor');
  /// }
  /// ```
  UniformVec4Slot getUniformVec4(String name) {
    final List<UniformFloatSlot> slots = _getSlotsForUniform(name, 4);
    return UniformVec4Slot._(slots[0], slots[1], slots[2], slots[3]);
  }

  /// Access the float binding for a mat2 uniform named [name].
  ///
  /// Example:
  ///
  /// ```glsl
  /// uniform mat2 uIdentity;
  /// ```
  ///
  /// ```dart
  /// void updateShader(ui.FragmentShader shader) {
  ///   shader.getUniformMat2('uIdentity');
  /// }
  /// ```
  UniformMat2Slot getUniformMat2(String name) {
    final List<UniformFloatSlot> slots = _getSlotsForUniform(name, 4);
    return UniformMat2Slot._(slots[0], slots[1], slots[2], slots[3]);
  }

  /// Access the float binding for a mat3 uniform named [name].
  ///
  /// Example:
  ///
  /// ```glsl
  /// uniform mat3 uIdentity;
  /// ```
  ///
  /// ```dart
  /// void updateShader(ui.FragmentShader shader) {
  ///   shader.getUniformMat3('uIdentity');
  /// }
  /// ```
  UniformMat3Slot getUniformMat3(String name) {
    final List<UniformFloatSlot> slots = _getSlotsForUniform(name, 9);
    return UniformMat3Slot._(
      slots[0],
      slots[1],
      slots[2],
      slots[3],
      slots[4],
      slots[5],
      slots[6],
      slots[7],
      slots[8],
    );
  }

  /// Access the float binding for a mat4 uniform named [name].
  ///
  /// Example:
  ///
  /// ```glsl
  /// uniform mat4 uIdentity;
  /// ```
  ///
  /// ```dart
  /// void updateShader(ui.FragmentShader shader) {
  ///   shader.getUniformMat4('uIdentity');
  /// }
  /// ```
  UniformMat4Slot getUniformMat4(String name) {
    final List<UniformFloatSlot> slots = _getSlotsForUniform(name, 16);
    return UniformMat4Slot._(
      slots[0],
      slots[1],
      slots[2],
      slots[3],
      slots[4],
      slots[5],
      slots[6],
      slots[7],
      slots[8],
      slots[9],
      slots[10],
      slots[11],
      slots[12],
      slots[13],
      slots[14],
      slots[15],
    );
  }

  UniformArray<T> _getUniformArray<T extends UniformType>(
    String name,
    int elementSize,
    T Function(List<UniformFloatSlot> slots) elementFactory,
  ) {
    final _UniformFloatInfo info = _program._getUniformFloatInfo(name);

    if (info.size % elementSize != 0) {
      throw ArgumentError(
        'Uniform size (${info.size}) for "$name" is not a multiple of $elementSize.',
      );
    }
    final int numElements = info.size ~/ elementSize;

    final elements = List<T>.generate(numElements, (i) {
      final slots = List<UniformFloatSlot>.generate(
        info.size,
        (j) => UniformFloatSlot._(this, name, j, info.index + i * elementSize + j),
      );
      _slots.addAll(slots.map((slot) => WeakReference<UniformFloatSlot>(slot)));
      return elementFactory(slots);
    });

    _slots.removeWhere((WeakReference<UniformFloatSlot> ref) => ref.target == null);

    return UniformArray<T>._(elements);
  }

  /// Access the binding for a float[] uniform named [name].
  ///
  /// Example:
  ///
  /// ```glsl
  /// uniform float[10] uValues;
  /// ```
  ///
  /// ```dart
  /// void updateShader(ui.FragmentShader shader) {
  ///   final ui.UniformArray<ui.UniformFloatSlot> values = shader.getUniformFloatArray('uValues');
  ///   values[2].set(1.0);
  /// }
  /// ```
  UniformArray<UniformFloatSlot> getUniformFloatArray(String name) {
    return _getUniformArray(name, 1, (components) => components.first);
  }

  /// Access the binding for a vec2[] uniform named [name].
  ///
  /// Example:
  ///
  /// ```glsl
  /// uniform vec2[10] uPositions;
  /// ```
  ///
  /// ```dart
  /// void updateShader(ui.FragmentShader shader) {
  ///   final ui.UniformArray<ui.UniformVec2Slot> positions = shader.getUniformVec2Array('uPositions');
  ///   positions[2].set(6.0, 7.0);
  /// }
  /// ```
  UniformArray<UniformVec2Slot> getUniformVec2Array(String name) {
    return _getUniformArray<UniformVec2Slot>(
      name,
      2, // 2 floats per element
      (components) => UniformVec2Slot._(
        components[0],
        components[1],
      ), // Create Vec2 from two UniformFloat components
    );
  }

  /// Access the binding for a vec3[] uniform named [name].
  ///
  /// Example:
  ///
  /// ```glsl
  /// uniform vec3[10] uColors;
  /// ```
  ///
  /// ```dart
  /// void updateShader(ui.FragmentShader shader) {
  ///   final ui.UniformArray<ui.UniformVec3Slot> colors = shader.getUniformVec3Array('uColors');
  ///   colors[0].set(1.0, 0.0, 1.0);
  /// }
  /// ```
  UniformArray<UniformVec3Slot> getUniformVec3Array(String name) {
    return _getUniformArray<UniformVec3Slot>(
      name,
      3, // 3 floats per element
      (components) => UniformVec3Slot._(components[0], components[1], components[2]), // Create Vec3
    );
  }

  /// Access the binding for a vec4[] uniform named [name].
  ///
  /// Example:
  ///
  /// ```glsl
  /// uniform vec4[10] uColors;
  /// ```
  ///
  /// ```dart
  /// void updateShader(ui.FragmentShader shader) {
  ///   final ui.UniformArray<ui.UniformVec4Slot> colors = shader.getUniformVec4Array('uColors');
  ///   colors[0].set(1.0, 0.0, 1.0, 0.5);
  /// }
  /// ```
  UniformArray<UniformVec4Slot> getUniformVec4Array(String name) {
    return _getUniformArray<UniformVec4Slot>(
      name,
      4, // 4 floats per element
      (components) => UniformVec4Slot._(
        components[0],
        components[1],
        components[2],
        components[3],
      ), // Create Vec4
    );
  }

  /// Access the binding for a mat2[] uniform named [name].
  ///
  /// Example:
  ///
  /// ```glsl
  /// uniform mat2[10] uMatricies;
  /// ```
  ///
  /// ```dart
  /// void updateShader(ui.FragmentShader shader) {
  ///   final ui.UniformArray<ui.UniformMat2Slot> mats = shader.getUniformMat2Array('uMatricies');
  ///   mats[0].set(
  ///     1.0, 0.0,
  ///     1.0, 0.5
  ///   );
  /// }
  /// ```
  UniformArray<UniformMat2Slot> getUniformMat2Array(String name) {
    return _getUniformArray<UniformMat2Slot>(
      name,
      4,
      (components) => UniformMat2Slot._(components[0], components[1], components[2], components[3]),
    );
  }

  /// Access the binding for a mat3[] uniform named [name].
  ///
  /// Example:
  ///
  /// ```glsl
  /// uniform mat3[10] uMatricies;
  /// ```
  ///
  /// ```dart
  /// void updateShader(ui.FragmentShader shader) {
  ///   final ui.UniformArray<ui.UniformMat3Slot> mats = shader.getUniformMat3Array('uMatricies');
  ///   mats[0].set(
  ///     1.0, 0.0, 0.0,
  ///     1.0, 0.5, 0.0,
  ///     1.0, 0.3, 1.2
  ///   );
  /// }
  /// ```
  UniformArray<UniformMat3Slot> getUniformMat3Array(String name) {
    return _getUniformArray<UniformMat3Slot>(
      name,
      9,
      (components) => UniformMat3Slot._(
        components[0],
        components[1],
        components[2],
        components[3],
        components[4],
        components[5],
        components[6],
        components[7],
        components[8],
      ),
    );
  }

  /// Access the binding for a mat4[] uniform named [name].
  ///
  /// Example:
  ///
  /// ```glsl
  /// uniform mat4[10] uMatricies;
  /// ```
  ///
  /// ```dart
  /// void updateShader(ui.FragmentShader shader) {
  ///   final ui.UniformArray<ui.UniformMat4Slot> mats = shader.getUniformMat4Array('uMatricies');
  ///   mats[0].set(
  ///     1.0, 0.0, 0.0, 1.0,
  ///     1.0, 0.5, 0.0, 0.4,
  ///     1.0, 0.3, 1.2, 0.2,
  ///     0.0, 0.0, 1.0, 0.3,
  ///   );
  /// }
  /// ```
  UniformArray<UniformMat4Slot> getUniformMat4Array(String name) {
    return _getUniformArray<UniformMat4Slot>(
      name,
      16, // 4 floats per element
      (components) => UniformMat4Slot._(
        components[0],
        components[1],
        components[2],
        components[3],
        components[4],
        components[5],
        components[6],
        components[7],
        components[8],
        components[9],
        components[10],
        components[11],
        components[12],
        components[13],
        components[14],
        components[15],
      ),
    );
  }

  /// Access the [ImageSamplerSlot] binding associated with the sampler named
  /// [name].
  ///
  /// The index provided to setImageSampler is the index of the sampler uniform
  /// defined in the fragment program, excluding all non-sampler uniforms.
  ImageSamplerSlot getImageSampler(String name) {
    final int index = _program._getImageSamplerIndex(name);
    final slot = ImageSamplerSlot._(this, name, index);
    _samplers.removeWhere((WeakReference<ImageSamplerSlot> ref) => ref.target == null);
    _samplers.add(WeakReference<ImageSamplerSlot>(slot));
    return slot;
  }

  /// Sets the sampler uniform at [index] to [image].
  ///
  /// The index provided to setImageSampler is the index of the sampler uniform defined
  /// in the fragment program, excluding all non-sampler uniforms.
  ///
  /// The optional [filterQuality] argument may be provided to set the quality level used to sample
  /// the image. By default, it is set to [FilterQuality.none].
  ///
  /// All the sampler uniforms that a shader expects must be provided or the
  /// results will be undefined.
  void setImageSampler(int index, Image image, {FilterQuality filterQuality = FilterQuality.none}) {
    assert(!debugDisposed, 'Tried to access uniforms on a disposed Shader: $this');
    assert(!image.debugDisposed, 'Image has been disposed');
    _setImageSampler(index, image._image, filterQuality.index);
  }

  /// Releases the native resources held by the [FragmentShader].
  ///
  /// After this method is called, calling methods on the shader, or attaching
  /// it to a [Paint] object will fail with an exception. Calling [dispose]
  /// twice will also result in an exception being thrown.
  @override
  void dispose() {
    super.dispose();
    _floats = _kEmptyFloat32List;
    _dispose();
  }

  @Native<Handle Function(Handle, Handle, Handle, Handle)>(symbol: 'ReusableFragmentShader::Create')
  external Float32List _constructor(
    FragmentProgram program,
    int floatUniforms,
    int samplerUniforms,
  );

  @Native<Void Function(Pointer<Void>, Handle, Handle, Int32)>(
    symbol: 'ReusableFragmentShader::SetImageSampler',
  )
  external void _setImageSampler(int index, _Image sampler, int filterQualityIndex);

  @Native<Bool Function(Pointer<Void>)>(symbol: 'ReusableFragmentShader::ValidateSamplers')
  external bool _validateSamplers();

  @Native<Bool Function(Pointer<Void>)>(symbol: 'ReusableFragmentShader::ValidateImageFilter')
  external bool _validateImageFilter();

  @Native<Void Function(Pointer<Void>)>(symbol: 'ReusableFragmentShader::Dispose')
  external void _dispose();
}

/// Defines how a list of points is interpreted when drawing a set of triangles.
///
/// Used by [Canvas.drawVertices].
// These enum values must be kept in sync with DlVertexMode.
enum VertexMode {
  /// Draw each sequence of three points as the vertices of a triangle.
  triangles,

  /// Draw each sliding window of three points as the vertices of a triangle.
  triangleStrip,

  /// Draw the first point and each sliding window of two points as the vertices
  /// of a triangle.
  ///
  /// This mode is not natively supported by most backends, and is instead
  /// implemented by unrolling the points into the equivalent
  /// [VertexMode.triangles], which is generally more efficient.
  triangleFan,
}

/// A set of vertex data used by [Canvas.drawVertices].
///
/// Vertex data consists of a series of points in the canvas coordinate space.
/// Based on the [VertexMode], these points are interpreted either as
/// independent triangles ([VertexMode.triangles]), as a sliding window of
/// points forming a chain of triangles each sharing one side with the next
/// ([VertexMode.triangleStrip]), or as a fan of triangles with a single shared
/// point ([VertexMode.triangleFan]).
///
/// Each point can be associated with a color. Each triangle is painted as a
/// gradient that blends between the three colors at the three points of that
/// triangle. If no colors are specified, transparent black is assumed for all
/// the points.
///
/// These colors are then blended with the [Paint] specified in the call to
/// [Canvas.drawVertices]. This paint is either a solid color ([Paint.color]),
/// or a bitmap, specified using a shader ([Paint.shader]), typically either a
/// gradient ([Gradient]) or image ([ImageFilter]). The bitmap uses the same
/// coordinate space as the canvas (in the case of an [ImageFilter], this is
/// notably different than the coordinate space of the source image; the source
/// image is tiled according to the filter's configuration, and the image that
/// is sampled when painting the triangles is the infinite one after all the
/// repeating is applied.)
///
/// Each point in the [Vertices] is associated with a specific point on this
/// image. Each triangle is painted by sampling points from this image by
/// interpolating between the three points of the image corresponding to the
/// three points of the triangle.
///
/// The [Vertices.new] constructor configures all this using lists of [Offset]
/// and [Color] objects. The [Vertices.raw] constructor instead uses
/// [Float32List], [Int32List], and [Uint16List] objects, which more closely
/// corresponds to the data format used internally and therefore reduces some of
/// the conversion overhead. The raw constructor is useful if the data is coming
/// from another source (e.g. a file) and can therefore be parsed directly into
/// the underlying representation.
base class Vertices extends NativeFieldWrapperClass1 {
  /// Creates a set of vertex data for use with [Canvas.drawVertices].
  ///
  /// The `mode` parameter describes how the points should be interpreted: as
  /// independent triangles ([VertexMode.triangles]), as a sliding window of
  /// points forming a chain of triangles each sharing one side with the next
  /// ([VertexMode.triangleStrip]), or as a fan of triangles with a single
  /// shared point ([VertexMode.triangleFan]).
  ///
  /// The `positions` parameter provides the points in the canvas space that
  /// will be use to draw the triangles.
  ///
  /// The `colors` parameter, if specified, provides the color for each point in
  /// `positions`. Each triangle is painted as a gradient that blends between
  /// the three colors at the three points of that triangle. (These colors are
  /// then blended with the [Paint] specified in the call to
  /// [Canvas.drawVertices].)
  ///
  /// The `textureCoordinates` parameter, if specified, provides the points in
  /// the [Paint] image to sample for the corresponding points in `positions`.
  ///
  /// If the `colors` or `textureCoordinates` parameters are specified, they must
  /// be the same length as `positions`.
  ///
  /// The `indices` parameter specifies the order in which the points should be
  /// painted. If it is omitted (or present but empty), the points are processed
  /// in the order they are given in `positions`, as if the `indices` was a list
  /// from 0 to n-1, where _n_ is the number of entries in `positions`. The
  /// `indices` parameter, if present and non-empty, must have at least three
  /// entries, but may be of any length beyond this. Indicies may refer to
  /// offsets in the positions array multiple times, or may skip positions
  /// entirely.
  ///
  /// If the `indices` parameter is specified, all values in the list must be
  /// valid index values for `positions`.
  ///
  /// The `mode` and `positions` parameters must not be null.
  ///
  /// This constructor converts its parameters into [dart:typed_data] lists
  /// (e.g. using [Float32List]s for the coordinates) before sending them to the
  /// Flutter engine. If the data provided to this constructor is not already in
  /// [List] form, consider using the [Vertices.raw] constructor instead to
  /// avoid converting the data twice.
  Vertices(
    VertexMode mode,
    List<Offset> positions, {
    List<Color>? colors,
    List<Offset>? textureCoordinates,
    List<int>? indices,
  }) {
    if (colors != null && colors.length != positions.length) {
      throw ArgumentError('"positions" and "colors" lengths must match.');
    }
    if (textureCoordinates != null && textureCoordinates.length != positions.length) {
      throw ArgumentError('"positions" and "textureCoordinates" lengths must match.');
    }
    assert(() {
      if (indices != null) {
        for (var index = 0; index < indices.length; index += 1) {
          if (indices[index] >= positions.length) {
            throw ArgumentError(
              '"indices" values must be valid indices in the positions list '
              '(i.e. numbers in the range 0..${positions.length - 1}), '
              'but indices[$index] is ${indices[index]}, which is too big.',
            );
          }
        }
      }
      return true;
    }());
    final Float32List encodedPositions = _encodePointList(positions);
    final Float32List? encodedTextureCoordinates = (textureCoordinates != null)
        ? _encodePointList(textureCoordinates)
        : null;
    final Int32List? encodedColors = colors != null ? _encodeColorList(colors) : null;
    final Uint16List? encodedIndices = indices != null ? Uint16List.fromList(indices) : null;

    if (!_init(
      this,
      mode.index,
      encodedPositions,
      encodedTextureCoordinates,
      encodedColors,
      encodedIndices,
    )) {
      throw ArgumentError('Invalid configuration for vertices.');
    }
  }

  /// Creates a set of vertex data for use with [Canvas.drawVertices], using the
  /// encoding expected by the Flutter engine.
  ///
  /// The `mode` parameter describes how the points should be interpreted: as
  /// independent triangles ([VertexMode.triangles]), as a sliding window of
  /// points forming a chain of triangles each sharing one side with the next
  /// ([VertexMode.triangleStrip]), or as a fan of triangles with a single
  /// shared point ([VertexMode.triangleFan]).
  ///
  /// The `positions` parameter provides the points in the canvas space that
  /// will be use to draw the triangles. Each point is represented as two
  /// numbers in the list, the first giving the x coordinate and the second
  /// giving the y coordinate. (As a result, the list must have an even number
  /// of entries.)
  ///
  /// The `colors` parameter, if specified, provides the color for each point in
  /// `positions`. Each color is represented as ARGB with 8 bit color channels
  /// (like [Color.value]'s internal representation), and the list, if
  /// specified, must therefore be half the length of `positions`. Each triangle
  /// is painted as a gradient that blends between the three colors at the three
  /// points of that triangle. (These colors are then blended with the [Paint]
  /// specified in the call to [Canvas.drawVertices].)
  ///
  /// The `textureCoordinates` parameter, if specified, provides the points in
  /// the [Paint] image to sample for the corresponding points in `positions`.
  /// Each point is represented as two numbers in the list, the first giving the
  /// x coordinate and the second giving the y coordinate. This list, if
  /// specified, must be the same length as `positions`.
  ///
  /// The `indices` parameter specifies the order in which the points should be
  /// painted. If it is omitted (or present but empty), the points are processed
  /// in the order they are given in `positions`, as if the `indices` was a list
  /// from 0 to n-2, where _n_ is the number of pairs in `positions` (i.e. half
  /// the length of `positions`). The `indices` parameter, if present and
  /// non-empty, must have at least three entries, but may be of any length
  /// beyond this. Indicies may refer to offsets in the positions array multiple
  /// times, or may skip positions entirely.
  ///
  /// If the `indices` parameter is specified, all values in the list must be
  /// valid index values for pairs in `positions`. For example, if there are 12
  /// numbers in `positions` (representing 6 coordinates), the `indicies` must
  /// be numbers in the range 0..5 inclusive.
  ///
  /// The `mode` and `positions` parameters must not be null.
  Vertices.raw(
    VertexMode mode,
    Float32List positions, {
    Int32List? colors,
    Float32List? textureCoordinates,
    Uint16List? indices,
  }) {
    if (positions.length % 2 != 0) {
      throw ArgumentError(
        '"positions" must have an even number of entries (each coordinate is an x,y pair).',
      );
    }
    if (colors != null && colors.length * 2 != positions.length) {
      throw ArgumentError('"positions" and "colors" lengths must match.');
    }
    if (textureCoordinates != null && textureCoordinates.length != positions.length) {
      throw ArgumentError('"positions" and "textureCoordinates" lengths must match.');
    }
    assert(() {
      if (indices != null) {
        for (var index = 0; index < indices.length; index += 1) {
          if (indices[index] * 2 >= positions.length) {
            throw ArgumentError(
              '"indices" values must be valid indices in the positions list '
              '(i.e. numbers in the range 0..${positions.length ~/ 2 - 1}), '
              'but indices[$index] is ${indices[index]}, which is too big.',
            );
          }
        }
      }
      return true;
    }());
    if (!_init(this, mode.index, positions, textureCoordinates, colors, indices)) {
      throw ArgumentError('Invalid configuration for vertices.');
    }
  }

  @Native<Bool Function(Handle, Int32, Handle, Handle, Handle, Handle)>(symbol: 'Vertices::init')
  external static bool _init(
    Vertices outVertices,
    int mode,
    Float32List positions,
    Float32List? textureCoordinates,
    Int32List? colors,
    Uint16List? indices,
  );

  /// Release the resources used by this object. The object is no longer usable
  /// after this method is called.
  void dispose() {
    assert(!_disposed);
    assert(() {
      _disposed = true;
      return true;
    }());
    _dispose();
  }

  /// This can't be a leaf call because the native function calls Dart API
  /// (Dart_SetNativeInstanceField).
  @Native<Void Function(Pointer<Void>)>(symbol: 'Vertices::dispose')
  external void _dispose();

  bool _disposed = false;

  /// Whether this reference to the underlying vertex data is [dispose]d.
  ///
  /// This only returns a valid value if asserts are enabled, and must not be
  /// used otherwise.
  bool get debugDisposed {
    bool? disposed;
    assert(() {
      disposed = _disposed;
      return true;
    }());
    return disposed ??
        (throw StateError('Vertices.debugDisposed is only available when asserts are enabled.'));
  }
}

/// Defines how a list of points is interpreted when drawing a set of points.
///
/// Used by [Canvas.drawPoints] and [Canvas.drawRawPoints].
// These enum values must be kept in sync with DlPointMode.
enum PointMode {
  /// Draw each point separately.
  ///
  /// If the [Paint.strokeCap] is [StrokeCap.round], then each point is drawn
  /// as a circle with the diameter of the [Paint.strokeWidth], filled as
  /// described by the [Paint] (ignoring [Paint.style]).
  ///
  /// Otherwise, each point is drawn as an axis-aligned square with sides of
  /// length [Paint.strokeWidth], filled as described by the [Paint] (ignoring
  /// [Paint.style]).
  points,

  /// Draw each sequence of two points as a line segment.
  ///
  /// If the number of points is odd, then the last point is ignored.
  ///
  /// The lines are stroked as described by the [Paint] (ignoring
  /// [Paint.style]).
  lines,

  /// Draw the entire sequence of points as one line.
  ///
  /// The lines are stroked as described by the [Paint] (ignoring
  /// [Paint.style]).
  polygon,
}

/// Defines how a new clip region should be merged with the existing clip
/// region.
///
/// Used by [Canvas.clipRect].
enum ClipOp {
  /// Subtract the new region from the existing region.
  difference,

  /// Intersect the new region from the existing region.
  intersect,
}

/// An interface for recording graphical operations.
///
/// [Canvas] objects are used in creating [Picture] objects, which can
/// themselves be used with a [SceneBuilder] to build a [Scene]. In
/// normal usage, however, this is all handled by the framework.
///
/// A canvas has a current transformation matrix which is applied to all
/// operations. Initially, the transformation matrix is the identity transform.
/// It can be modified using the [translate], [scale], [rotate], [skew],
/// and [transform] methods.
///
/// A canvas also has a current clip region which is applied to all operations.
/// Initially, the clip region is infinite. It can be modified using the
/// [clipRect], [clipRRect], and [clipPath] methods.
///
/// The current transform and clip can be saved and restored using the stack
/// managed by the [save], [saveLayer], and [restore] methods.
///
/// ## Use with the Flutter framework
///
/// The Flutter framework's [RendererBinding] provides a hook for creating
/// [Canvas] objects ([RendererBinding.createCanvas]) that allows tests to hook
/// into the scene creation logic. When creating a [Canvas] that will be used
/// with a [PictureLayer] as part of the [Scene] in the context of the Flutter
/// framework, consider calling [RendererBinding.createCanvas] instead of
/// calling the [Canvas.new] constructor directly.
///
/// This does not apply when using a canvas to generate a bitmap for other
/// purposes, e.g. for generating a PNG image using [Picture.toImage].
abstract class Canvas {
  /// Creates a canvas for recording graphical operations into the
  /// given picture recorder.
  ///
  /// Graphical operations that affect pixels entirely outside the given
  /// `cullRect` might be discarded by the implementation. However, the
  /// implementation might draw outside these bounds if, for example, a command
  /// draws partially inside and outside the `cullRect`. To ensure that pixels
  /// outside a given region are discarded, consider using a [clipRect]. The
  /// `cullRect` is optional; by default, all operations are kept.
  ///
  /// To end the recording, call [PictureRecorder.endRecording] on the
  /// given recorder.
  factory Canvas(PictureRecorder recorder, [Rect? cullRect]) = _NativeCanvas;

  /// Saves a copy of the current transform and clip on the save stack.
  ///
  /// Call [restore] to pop the save stack.
  ///
  /// See also:
  ///
  ///  * [saveLayer], which does the same thing but additionally also groups the
  ///    commands done until the matching [restore].
  void save();

  /// Saves a copy of the current transform and clip on the save stack, and then
  /// creates a new group which subsequent calls will become a part of. When the
  /// save stack is later popped, the group will be flattened into a layer and
  /// have the given `paint`'s [Paint.colorFilter] and [Paint.blendMode]
  /// applied.
  ///
  /// This lets you create composite effects, for example making a group of
  /// drawing commands semi-transparent. Without using [saveLayer], each part of
  /// the group would be painted individually, so where they overlap would be
  /// darker than where they do not. By using [saveLayer] to group them
  /// together, they can be drawn with an opaque color at first, and then the
  /// entire group can be made transparent using the [saveLayer]'s paint.
  ///
  /// Call [restore] to pop the save stack and apply the paint to the group.
  ///
  /// ## Using saveLayer with clips
  ///
  /// When a rectangular clip operation (from [clipRect]) is not axis-aligned
  /// with the raster buffer, or when the clip operation is not rectilinear
  /// (e.g. because it is a rounded rectangle clip created by [clipRRect] or an
  /// arbitrarily complicated path clip created by [clipPath]), the edge of the
  /// clip needs to be anti-aliased.
  ///
  /// If two draw calls overlap at the edge of such a clipped region, without
  /// using [saveLayer], the first drawing will be anti-aliased with the
  /// background first, and then the second will be anti-aliased with the result
  /// of blending the first drawing and the background. On the other hand, if
  /// [saveLayer] is used immediately after establishing the clip, the second
  /// drawing will cover the first in the layer, and thus the second alone will
  /// be anti-aliased with the background when the layer is clipped and
  /// composited (when [restore] is called).
  ///
  /// For example, this [CustomPainter.paint] method paints a clean white
  /// rounded rectangle:
  ///
  /// ```dart
  /// void paint(Canvas canvas, Size size) {
  ///   Rect rect = Offset.zero & size;
  ///   canvas.save();
  ///   canvas.clipRRect(RRect.fromRectXY(rect, 100.0, 100.0));
  ///   canvas.saveLayer(rect, Paint());
  ///   canvas.drawPaint(Paint()..color = Colors.red);
  ///   canvas.drawPaint(Paint()..color = Colors.white);
  ///   canvas.restore();
  ///   canvas.restore();
  /// }
  /// ```
  ///
  /// On the other hand, this one renders a red outline, the result of the red
  /// paint being anti-aliased with the background at the clip edge, then the
  /// white paint being similarly anti-aliased with the background _including
  /// the clipped red paint_:
  ///
  /// ```dart
  /// void paint(Canvas canvas, Size size) {
  ///   // (this example renders poorly, prefer the example above)
  ///   Rect rect = Offset.zero & size;
  ///   canvas.save();
  ///   canvas.clipRRect(RRect.fromRectXY(rect, 100.0, 100.0));
  ///   canvas.drawPaint(Paint()..color = Colors.red);
  ///   canvas.drawPaint(Paint()..color = Colors.white);
  ///   canvas.restore();
  /// }
  /// ```
  ///
  /// This point is moot if the clip only clips one draw operation. For example,
  /// the following paint method paints a pair of clean white rounded
  /// rectangles, even though the clips are not done on a separate layer:
  ///
  /// ```dart
  /// void paint(Canvas canvas, Size size) {
  ///   canvas.save();
  ///   canvas.clipRRect(RRect.fromRectXY(Offset.zero & (size / 2.0), 50.0, 50.0));
  ///   canvas.drawPaint(Paint()..color = Colors.white);
  ///   canvas.restore();
  ///   canvas.save();
  ///   canvas.clipRRect(RRect.fromRectXY(size.center(Offset.zero) & (size / 2.0), 50.0, 50.0));
  ///   canvas.drawPaint(Paint()..color = Colors.white);
  ///   canvas.restore();
  /// }
  /// ```
  ///
  /// (Incidentally, rather than using [clipRRect] and [drawPaint] to draw
  /// rounded rectangles like this, prefer the [drawRRect] method. These
  /// examples are using [drawPaint] as a proxy for "complicated draw operations
  /// that will get clipped", to illustrate the point.)
  ///
  /// ## Performance considerations
  ///
  /// Generally speaking, [saveLayer] is relatively expensive.
  ///
  /// There are a several different hardware architectures for GPUs (graphics
  /// processing units, the hardware that handles graphics), but most of them
  /// involve batching commands and reordering them for performance. When layers
  /// are used, they cause the rendering pipeline to have to switch render
  /// target (from one layer to another). Render target switches can flush the
  /// GPU's command buffer, which typically means that optimizations that one
  /// could get with larger batching are lost. Render target switches also
  /// generate a lot of memory churn because the GPU needs to copy out the
  /// current frame buffer contents from the part of memory that's optimized for
  /// writing, and then needs to copy it back in once the previous render target
  /// (layer) is restored.
  ///
  /// See also:
  ///
  ///  * [save], which saves the current state, but does not create a new layer
  ///    for subsequent commands.
  ///  * [BlendMode], which discusses the use of [Paint.blendMode] with
  ///    [saveLayer].
  void saveLayer(Rect? bounds, Paint paint);

  /// Pops the current save stack, if there is anything to pop.
  /// Otherwise, does nothing.
  ///
  /// Use [save] and [saveLayer] to push state onto the stack.
  ///
  /// If the state was pushed with [saveLayer], then this call will also
  /// cause the new layer to be composited into the previous layer.
  void restore();

  /// Restores the save stack to a previous level as might be obtained from [getSaveCount].
  /// If [count] is less than 1, the stack is restored to its initial state.
  /// If [count] is greater than the current [getSaveCount] then nothing happens.
  ///
  /// Use [save] and [saveLayer] to push state onto the stack.
  ///
  /// If any of the state stack levels restored by this call were pushed with
  /// [saveLayer], then this call will also cause those layers to be composited
  /// into their previous layers.
  void restoreToCount(int count);

  /// Returns the number of items on the save stack, including the
  /// initial state. This means it returns 1 for a clean canvas, and
  /// that each call to [save] and [saveLayer] increments it, and that
  /// each matching call to [restore] decrements it.
  ///
  /// This number cannot go below 1.
  int getSaveCount();

  /// Add a translation to the current transform, shifting the coordinate space
  /// horizontally by the first argument and vertically by the second argument.
  void translate(double dx, double dy);

  /// Add an axis-aligned scale to the current transform, scaling by the first
  /// argument in the horizontal direction and the second in the vertical
  /// direction.
  ///
  /// If [sy] is unspecified, [sx] will be used for the scale in both
  /// directions.
  void scale(double sx, [double? sy]);

  /// Add a rotation to the current transform. The argument is in radians clockwise.
  void rotate(double radians);

  /// Add an axis-aligned skew to the current transform, with the first argument
  /// being the horizontal skew in rise over run units clockwise around the
  /// origin, and the second argument being the vertical skew in rise over run
  /// units clockwise around the origin.
  void skew(double sx, double sy);

  /// Multiply the current transform by the specified 4⨉4 transformation matrix
  /// specified as a list of values in column-major order.
  void transform(Float64List matrix4);

  /// Returns the current transform including the combined result of all transform
  /// methods executed since the creation of this [Canvas] object, and respecting the
  /// save/restore history.
  ///
  /// Methods that can change the current transform include [translate], [scale],
  /// [rotate], [skew], and [transform]. The [restore] method can also modify
  /// the current transform by restoring it to the same value it had before its
  /// associated [save] or [saveLayer] call.
  Float64List getTransform();

  /// Reduces the clip region to the intersection of the current clip and the
  /// given rectangle.
  ///
  /// ![](https://flutter.github.io/assets-for-api-docs/assets/dart-ui/clip_rect.png)
  ///
  /// If [doAntiAlias] is true, then the clip will be anti-aliased.
  ///
  /// If multiple draw commands intersect with the clip boundary, this can result
  /// in incorrect blending at the clip boundary. See [saveLayer] for a
  /// discussion of how to address that.
  ///
  /// Use [ClipOp.difference] to subtract the provided rectangle from the
  /// current clip.
  void clipRect(Rect rect, {ClipOp clipOp = ClipOp.intersect, bool doAntiAlias = true});

  /// Reduces the clip region to the intersection of the current clip and the
  /// given rounded rectangle.
  ///
  /// ![](https://flutter.github.io/assets-for-api-docs/assets/dart-ui/clip_rrect.png)
  ///
  /// If [doAntiAlias] is true, then the clip will be anti-aliased.
  ///
  /// If multiple draw commands intersect with the clip boundary, this can result
  /// in incorrect blending at the clip boundary. See [saveLayer] for a
  /// discussion of how to address that and some examples of using [clipRRect].
  void clipRRect(RRect rrect, {bool doAntiAlias = true});

  /// Reduces the clip region to the intersection of the current clip and the
  /// given rounded superellipse.
  ///
  /// ![](https://flutter.github.io/assets-for-api-docs/assets/dart-ui/clip_rsuperellipse.png)
  ///
  /// If [doAntiAlias] is true, then the clip will be anti-aliased.
  ///
  /// If multiple draw commands intersect with the clip boundary, this can result
  /// in incorrect blending at the clip boundary. See [saveLayer] for a
  /// discussion of how to address that and some examples of using [clipRSuperellipse].
  void clipRSuperellipse(RSuperellipse rsuperellipse, {bool doAntiAlias = true});

  /// Reduces the clip region to the intersection of the current clip and the
  /// given [Path].
  ///
  /// ![](https://flutter.github.io/assets-for-api-docs/assets/dart-ui/clip_path.png)
  ///
  /// If [doAntiAlias] is true, then the clip will be anti-aliased.
  ///
  /// If multiple draw commands intersect with the clip boundary, this can result
  /// in incorrect blending at the clip boundary. See [saveLayer] for a
  /// discussion of how to address that.
  void clipPath(Path path, {bool doAntiAlias = true});

  /// Returns the conservative bounds of the combined result of all clip methods
  /// executed within the current save stack of this [Canvas] object, as measured
  /// in the local coordinate space under which rendering operations are currently
  /// performed.
  ///
  /// The combined clip results are rounded out to an integer pixel boundary before
  /// they are transformed back into the local coordinate space which accounts for
  /// the pixel roundoff in rendering operations, particularly when antialiasing.
  /// Because the [Picture] may eventually be rendered into a scene within the
  /// context of transforming widgets or layers, the result may thus be overly
  /// conservative due to premature rounding. Using the [getDestinationClipBounds]
  /// method combined with the external transforms and rounding in the true device
  /// coordinate system will produce more accurate results, but this value may
  /// provide a more convenient approximation to compare rendering operations to
  /// the established clip.
  ///
  /// {@template dart.ui.canvas.conservativeClipBounds}
  /// The conservative estimate of the bounds is based on intersecting the bounds
  /// of each clip method that was executed with [ClipOp.intersect] and potentially
  /// ignoring any clip method that was executed with [ClipOp.difference]. The
  /// [ClipOp] argument is only present on the [clipRect] method.
  ///
  /// To understand how the bounds estimate can be conservative, consider the
  /// following two clip method calls:
  ///
  /// ```dart
  /// void draw(Canvas canvas) {
  ///   canvas.clipPath(Path()
  ///     ..addRect(const Rect.fromLTRB(10, 10, 20, 20))
  ///     ..addRect(const Rect.fromLTRB(80, 80, 100, 100)));
  ///   canvas.clipPath(Path()
  ///     ..addRect(const Rect.fromLTRB(80, 10, 100, 20))
  ///     ..addRect(const Rect.fromLTRB(10, 80, 20, 100)));
  ///   // ...
  /// }
  /// ```
  ///
  /// After executing both of those calls there is no area left in which to draw
  /// because the two paths have no overlapping regions. But, in this case,
  /// [getLocalClipBounds] would return a rectangle from `10, 10` to `100, 100` because it
  /// only intersects the bounds of the two path objects to obtain its conservative
  /// estimate.
  ///
  /// The clip bounds are not affected by the bounds of any enclosing
  /// [saveLayer] call as the engine does not currently guarantee the strict
  /// enforcement of those bounds during rendering.
  ///
  /// Methods that can change the current clip include [clipRect], [clipRRect],
  /// and [clipPath]. The [restore] method can also modify the current clip by
  /// restoring it to the same value it had before its associated [save] or
  /// [saveLayer] call.
  /// {@endtemplate}
  Rect getLocalClipBounds();

  /// Returns the conservative bounds of the combined result of all clip methods
  /// executed within the current save stack of this [Canvas] object, as measured
  /// in the destination coordinate space in which the [Picture] will be rendered.
  ///
  /// Unlike [getLocalClipBounds], the bounds are not rounded out to an integer
  /// pixel boundary as the Destination coordinate space may not represent pixels
  /// if the [Picture] being constructed will be further transformed when it is
  /// rendered or added to a scene. In order to determine the true pixels being
  /// affected, those external transforms should be applied first before rounding
  /// out the result to integer pixel boundaries. Most typically, [Picture] objects
  /// are rendered in a scene with a scale transform representing the Device Pixel
  /// Ratio.
  ///
  /// {@macro dart.ui.canvas.conservativeClipBounds}
  Rect getDestinationClipBounds();

  /// Paints the given [Color] onto the canvas, applying the given
  /// [BlendMode], with the given color being the source and the background
  /// being the destination.
  void drawColor(Color color, BlendMode blendMode);

  /// Draws a line between the given points using the given paint. The line is
  /// stroked, the value of the [Paint.style] is ignored for this call.
  ///
  /// The `p1` and `p2` arguments are interpreted as offsets from the origin.
  ///
  /// ![](https://flutter.github.io/assets-for-api-docs/assets/dart-ui/canvas_line.png#gh-light-mode-only)
  /// ![](https://flutter.github.io/assets-for-api-docs/assets/dart-ui/canvas_line_dark.png#gh-dark-mode-only)
  void drawLine(Offset p1, Offset p2, Paint paint);

  /// Fills the canvas with the given [Paint].
  ///
  /// To fill the canvas with a solid color and blend mode, consider
  /// [drawColor] instead.
  void drawPaint(Paint paint);

  /// Draws a rectangle with the given [Paint]. Whether the rectangle is filled
  /// or stroked (or both) is controlled by [Paint.style].
  ///
  /// ![](https://flutter.github.io/assets-for-api-docs/assets/dart-ui/canvas_rect.png#gh-light-mode-only)
  /// ![](https://flutter.github.io/assets-for-api-docs/assets/dart-ui/canvas_rect_dark.png#gh-dark-mode-only)
  void drawRect(Rect rect, Paint paint);

  /// Draws a rounded rectangle with the given [Paint]. Whether the rectangle is
  /// filled or stroked (or both) is controlled by [Paint.style].
  ///
  /// ![](https://flutter.github.io/assets-for-api-docs/assets/dart-ui/canvas_rrect.png#gh-light-mode-only)
  /// ![](https://flutter.github.io/assets-for-api-docs/assets/dart-ui/canvas_rrect_dark.png#gh-dark-mode-only)
  void drawRRect(RRect rrect, Paint paint);

  /// Draws a shape consisting of the difference between two rounded rectangles
  /// with the given [Paint]. Whether this shape is filled or stroked (or both)
  /// is controlled by [Paint.style].
  ///
  /// This shape is almost but not quite entirely unlike an annulus.
  void drawDRRect(RRect outer, RRect inner, Paint paint);

  /// Draws a rounded superellipse with the given [Paint]. The shape is filled,
  /// and the value of the [Paint.style] is ignored for this call.
  ///
  /// ![](https://flutter.github.io/assets-for-api-docs/assets/dart-ui/canvas_rsuperellipse.png#gh-light-mode-only)
  /// ![](https://flutter.github.io/assets-for-api-docs/assets/dart-ui/canvas_rsuperellipse.png#gh-dark-mode-only)
  void drawRSuperellipse(RSuperellipse rsuperellipse, Paint paint);

  /// Draws an axis-aligned oval that fills the given axis-aligned rectangle
  /// with the given [Paint]. Whether the oval is filled or stroked (or both) is
  /// controlled by [Paint.style].
  ///
  /// ![](https://flutter.github.io/assets-for-api-docs/assets/dart-ui/canvas_oval.png#gh-light-mode-only)
  /// ![](https://flutter.github.io/assets-for-api-docs/assets/dart-ui/canvas_oval_dark.png#gh-dark-mode-only)
  void drawOval(Rect rect, Paint paint);

  /// Draws a circle centered at the point given by the first argument and
  /// that has the radius given by the second argument, with the [Paint] given in
  /// the third argument. Whether the circle is filled or stroked (or both) is
  /// controlled by [Paint.style].
  ///
  /// ![](https://flutter.github.io/assets-for-api-docs/assets/dart-ui/canvas_circle.png#gh-light-mode-only)
  /// ![](https://flutter.github.io/assets-for-api-docs/assets/dart-ui/canvas_circle_dark.png#gh-dark-mode-only)
  void drawCircle(Offset c, double radius, Paint paint);

  /// Draw an arc scaled to fit inside the given rectangle.
  ///
  /// It starts from `startAngle` radians around the oval up to
  /// `startAngle` + `sweepAngle` radians around the oval, with zero radians
  /// being the point on the right hand side of the oval that crosses the
  /// horizontal line that intersects the center of the rectangle and with positive
  /// angles going clockwise around the oval. If `useCenter` is true, the arc is
  /// closed back to the center, forming a circle sector. Otherwise, the arc is
  /// not closed, forming a circle segment.
  ///
  /// ![](https://flutter.github.io/assets-for-api-docs/assets/dart-ui/canvas_draw_arc.png#gh-light-mode-only)
  /// ![](https://flutter.github.io/assets-for-api-docs/assets/dart-ui/canvas_draw_arc_dark.png#gh-dark-mode-only)
  ///
  /// This method is optimized for drawing arcs and should be faster than [Path.arcTo].
  void drawArc(Rect rect, double startAngle, double sweepAngle, bool useCenter, Paint paint);

  /// Draws the given [Path] with the given [Paint].
  ///
  /// Whether this shape is filled or stroked (or both) is controlled by
  /// [Paint.style]. If the path is filled, then sub-paths within it are
  /// implicitly closed (see [Path.close]).
  ///
  /// When drawing simple shapes (such as rectangles, ovals, or rounded
  /// rectangles), prefer using methods such as [drawRect], [drawOval], or
  /// [drawRRect] over [drawPath]. Methods that draw simple shapes are generally
  /// more efficient than drawing a [Path].
  void drawPath(Path path, Paint paint);

  /// Draws the given [Image] into the canvas with its top-left corner at the
  /// given [Offset]. The image is composited into the canvas using the given [Paint].
  void drawImage(Image image, Offset offset, Paint paint);

  /// Draws the subset of the given image described by the `src` argument into
  /// the canvas in the axis-aligned rectangle given by the `dst` argument.
  ///
  /// This might sample from outside the `src` rect by up to half the width of
  /// an applied filter.
  ///
  /// Multiple calls to this method with different arguments (from the same
  /// image) can be batched into a single call to [drawAtlas] to improve
  /// performance.
  void drawImageRect(Image image, Rect src, Rect dst, Paint paint);

  /// Draws the given [Image] into the canvas using the given [Paint].
  ///
  /// The image is drawn in nine portions described by splitting the image by
  /// drawing two horizontal lines and two vertical lines, where the `center`
  /// argument describes the rectangle formed by the four points where these
  /// four lines intersect each other. (This forms a 3-by-3 grid of regions,
  /// the center region being described by the `center` argument.)
  ///
  /// The four regions in the corners are drawn, without scaling, in the four
  /// corners of the destination rectangle described by `dst`. The remaining
  /// five regions are drawn by stretching them to fit such that they exactly
  /// cover the destination rectangle while maintaining their relative
  /// positions.
  void drawImageNine(Image image, Rect center, Rect dst, Paint paint);

  /// Draw the given picture onto the canvas. To create a picture, see
  /// [PictureRecorder].
  void drawPicture(Picture picture);

  /// Draws the text in the given [Paragraph] into this canvas at the given
  /// [Offset].
  ///
  /// The [Paragraph] object must have had [Paragraph.layout] called on it
  /// first.
  ///
  /// To align the text, set the `textAlign` on the [ParagraphStyle] object
  /// passed to the [ParagraphBuilder.new] constructor. For more details see
  /// [TextAlign] and the discussion at [ParagraphStyle.new].
  ///
  /// If the text is left aligned or justified, the left margin will be at the
  /// position specified by the `offset` argument's [Offset.dx] coordinate.
  ///
  /// If the text is right aligned or justified, the right margin will be at the
  /// position described by adding the [ParagraphConstraints.width] given to
  /// [Paragraph.layout], to the `offset` argument's [Offset.dx] coordinate.
  ///
  /// If the text is centered, the centering axis will be at the position
  /// described by adding half of the [ParagraphConstraints.width] given to
  /// [Paragraph.layout], to the `offset` argument's [Offset.dx] coordinate.
  void drawParagraph(Paragraph paragraph, Offset offset);

  /// Draws a sequence of points according to the given [PointMode].
  ///
  /// The `points` argument is interpreted as offsets from the origin.
  ///
  /// The `paint` is used for each point ([PointMode.points]) or line
  /// ([PointMode.lines] or [PointMode.polygon]), ignoring [Paint.style].
  ///
  /// See also:
  ///
  ///  * [drawRawPoints], which takes `points` as a [Float32List] rather than a
  ///    [List<Offset>].
  void drawPoints(PointMode pointMode, List<Offset> points, Paint paint);

  /// Draws a sequence of points according to the given [PointMode].
  ///
  /// The `points` argument is interpreted as a list of pairs of floating point
  /// numbers, where each pair represents an x and y offset from the origin.
  ///
  /// The `paint` is used for each point ([PointMode.points]) or line
  /// ([PointMode.lines] or [PointMode.polygon]), ignoring [Paint.style].
  ///
  /// See also:
  ///
  ///  * [drawPoints], which takes `points` as a [List<Offset>] rather than a
  ///    [List<Float32List>].
  void drawRawPoints(PointMode pointMode, Float32List points, Paint paint);

  /// Draws a set of [Vertices] onto the canvas as one or more triangles.
  ///
  /// The [Paint.color] property specifies the default color to use for the
  /// triangles.
  ///
  /// The [Paint.shader] property, if set, overrides the color entirely,
  /// replacing it with the colors from the specified [ImageShader], [Gradient],
  /// or other shader.
  ///
  /// The `blendMode` parameter is used to control how the colors in the
  /// `vertices` are combined with the colors in the `paint`. If there are no
  /// colors specified in `vertices` then the `blendMode` has no effect. If
  /// there are colors in the `vertices`, then the color taken from the
  /// [Paint.shader] or [Paint.color] in the `paint` is blended with the colors
  /// specified in the `vertices` using the `blendMode` parameter. For the
  /// purposes of this blending, the colors from the `paint` parameter are
  /// considered the source, and the colors from the `vertices` are considered
  /// the destination. [BlendMode.dst] ignores the `paint` and uses only the
  /// colors of the `vertices`; [BlendMode.src] ignores the colors of the
  /// `vertices` and uses only the colors in the `paint`.
  ///
  /// All parameters must not be null.
  ///
  /// See also:
  ///   * [Vertices.new], which creates a set of vertices to draw on the canvas.
  ///   * [Vertices.raw], which creates the vertices using typed data lists
  ///     rather than unencoded lists.
  ///   * [paint], Image shaders can be used to draw images on a triangular mesh.
  void drawVertices(Vertices vertices, BlendMode blendMode, Paint paint);

  /// Draws many parts of an image - the [atlas] - onto the canvas.
  ///
  /// This method allows for optimization when you want to draw many parts of an
  /// image onto the canvas, such as when using sprites or zooming. It is more efficient
  /// than using multiple calls to [drawImageRect] and provides more functionality
  /// to individually transform each image part by a separate rotation or scale and
  /// blend or modulate those parts with a solid color.
  ///
  /// The method takes a list of [Rect] objects that each define a piece of the
  /// [atlas] image to be drawn independently. Each [Rect] is associated with an
  /// [RSTransform] entry in the [transforms] list which defines the location,
  /// rotation, and (uniform) scale with which to draw that portion of the image.
  /// Each [Rect] can also be associated with an optional [Color] which will be
  /// composed with the associated image part using the [blendMode] before blending
  /// the result onto the canvas. The full operation can be broken down as:
  ///
  /// - Blend each rectangular portion of the image specified by an entry in the
  /// [rects] argument with its associated entry in the [colors] list using the
  /// [blendMode] argument (if a color is specified). In this part of the operation,
  /// the image part will be considered the source of the operation and the associated
  /// color will be considered the destination.
  /// - Blend the result from the first step onto the canvas using the translation,
  /// rotation, and scale properties expressed in the associated entry in the
  /// [transforms] list using the properties of the [Paint] object.
  ///
  /// If the first stage of the operation which blends each part of the image with
  /// a color is needed, then both the [colors] and [blendMode] arguments must
  /// not be null and there must be an entry in the [colors] list for each
  /// image part. If that stage is not needed, then the [colors] argument can
  /// be either null or an empty list and the [blendMode] argument may also be null.
  ///
  /// The optional [cullRect] argument can provide an estimate of the bounds of the
  /// coordinates rendered by all components of the atlas to be compared against
  /// the clip to quickly reject the operation if it does not intersect.
  ///
  /// An example usage to render many sprites from a single sprite atlas with no
  /// rotations or scales:
  ///
  /// ```dart
  /// class Sprite {
  ///   Sprite(this.index, this.center);
  ///   int index;
  ///   Offset center;
  /// }
  ///
  /// class MyPainter extends CustomPainter {
  ///   MyPainter(this.spriteAtlas, this.allSprites);
  ///
  ///   // assume spriteAtlas contains N 10x10 sprites side by side in a (N*10)x10 image
  ///   ui.Image spriteAtlas;
  ///   List<Sprite> allSprites;
  ///
  ///   @override
  ///   void paint(Canvas canvas, Size size) {
  ///     Paint paint = Paint();
  ///     canvas.drawAtlas(spriteAtlas, <RSTransform>[
  ///       for (final Sprite sprite in allSprites)
  ///         RSTransform.fromComponents(
  ///           rotation: 0.0,
  ///           scale: 1.0,
  ///           // Center of the sprite relative to its rect
  ///           anchorX: 5.0,
  ///           anchorY: 5.0,
  ///           // Location at which to draw the center of the sprite
  ///           translateX: sprite.center.dx,
  ///           translateY: sprite.center.dy,
  ///         ),
  ///     ], <Rect>[
  ///       for (final Sprite sprite in allSprites)
  ///         Rect.fromLTWH(sprite.index * 10.0, 0.0, 10.0, 10.0),
  ///     ], null, null, null, paint);
  ///   }
  ///
  ///   // ...
  /// }
  /// ```
  ///
  /// Another example usage which renders sprites with an optional opacity and rotation:
  ///
  /// ```dart
  /// class Sprite {
  ///   Sprite(this.index, this.center, this.alpha, this.rotation);
  ///   int index;
  ///   Offset center;
  ///   int alpha;
  ///   double rotation;
  /// }
  ///
  /// class MyPainter extends CustomPainter {
  ///   MyPainter(this.spriteAtlas, this.allSprites);
  ///
  ///   // assume spriteAtlas contains N 10x10 sprites side by side in a (N*10)x10 image
  ///   ui.Image spriteAtlas;
  ///   List<Sprite> allSprites;
  ///
  ///   @override
  ///   void paint(Canvas canvas, Size size) {
  ///     Paint paint = Paint();
  ///     canvas.drawAtlas(spriteAtlas, <RSTransform>[
  ///       for (final Sprite sprite in allSprites)
  ///         RSTransform.fromComponents(
  ///           rotation: sprite.rotation,
  ///           scale: 1.0,
  ///           // Center of the sprite relative to its rect
  ///           anchorX: 5.0,
  ///           anchorY: 5.0,
  ///           // Location at which to draw the center of the sprite
  ///           translateX: sprite.center.dx,
  ///           translateY: sprite.center.dy,
  ///         ),
  ///     ], <Rect>[
  ///       for (final Sprite sprite in allSprites)
  ///         Rect.fromLTWH(sprite.index * 10.0, 0.0, 10.0, 10.0),
  ///     ], <Color>[
  ///       for (final Sprite sprite in allSprites)
  ///         Colors.white.withAlpha(sprite.alpha),
  ///     ], BlendMode.srcIn, null, paint);
  ///   }
  ///
  ///   // ...
  /// }
  /// ```
  ///
  /// The length of the [transforms] and [rects] lists must be equal and
  /// if the [colors] argument is not null then it must either be empty or
  /// have the same length as the other two lists.
  ///
  /// See also:
  ///
  ///  * [drawRawAtlas], which takes its arguments as typed data lists rather
  ///    than objects.
  void drawAtlas(
    Image atlas,
    List<RSTransform> transforms,
    List<Rect> rects,
    List<Color>? colors,
    BlendMode? blendMode,
    Rect? cullRect,
    Paint paint,
  );

  /// Draws many parts of an image - the [atlas] - onto the canvas.
  ///
  /// This method allows for optimization when you want to draw many parts of an
  /// image onto the canvas, such as when using sprites or zooming. It is more efficient
  /// than using multiple calls to [drawImageRect] and provides more functionality
  /// to individually transform each image part by a separate rotation or scale and
  /// blend or modulate those parts with a solid color. It is also more efficient
  /// than [drawAtlas] as the data in the arguments is already packed in a format
  /// that can be directly used by the rendering code.
  ///
  /// A full description of how this method uses its arguments to draw onto the
  /// canvas can be found in the description of the [drawAtlas] method.
  ///
  /// The [rstTransforms] argument is interpreted as a list of four-tuples, with
  /// each tuple being ([RSTransform.scos], [RSTransform.ssin],
  /// [RSTransform.tx], [RSTransform.ty]).
  ///
  /// The [rects] argument is interpreted as a list of four-tuples, with each
  /// tuple being ([Rect.left], [Rect.top], [Rect.right], [Rect.bottom]).
  ///
  /// The [colors] argument, which can be null, is interpreted as a list of
  /// 32-bit colors, with the same packing as [Color.value]. If the [colors]
  /// argument is not null then the [blendMode] argument must also not be null.
  ///
  /// An example usage to render many sprites from a single sprite atlas with no rotations
  /// or scales:
  ///
  /// ```dart
  /// class Sprite {
  ///   Sprite(this.index, this.center);
  ///   int index;
  ///   Offset center;
  /// }
  ///
  /// class MyPainter extends CustomPainter {
  ///   MyPainter(this.spriteAtlas, this.allSprites);
  ///
  ///   // assume spriteAtlas contains N 10x10 sprites side by side in a (N*10)x10 image
  ///   ui.Image spriteAtlas;
  ///   List<Sprite> allSprites;
  ///
  ///   @override
  ///   void paint(Canvas canvas, Size size) {
  ///     // For best advantage, these lists should be cached and only specific
  ///     // entries updated when the sprite information changes. This code is
  ///     // illustrative of how to set up the data and not a recommendation for
  ///     // optimal usage.
  ///     Float32List rectList = Float32List(allSprites.length * 4);
  ///     Float32List transformList = Float32List(allSprites.length * 4);
  ///     for (int i = 0; i < allSprites.length; i++) {
  ///       Sprite sprite = allSprites[i];
  ///       final double rectX = sprite.index * 10.0;
  ///       rectList[i * 4 + 0] = rectX;
  ///       rectList[i * 4 + 1] = 0.0;
  ///       rectList[i * 4 + 2] = rectX + 10.0;
  ///       rectList[i * 4 + 3] = 10.0;
  ///
  ///       // This example sets the RSTransform values directly for a common case of no
  ///       // rotations or scales and just a translation to position the atlas entry. For
  ///       // more complicated transforms one could use the RSTransform class to compute
  ///       // the necessary values or do the same math directly.
  ///       transformList[i * 4 + 0] = 1.0;
  ///       transformList[i * 4 + 1] = 0.0;
  ///       transformList[i * 4 + 2] = sprite.center.dx - 5.0;
  ///       transformList[i * 4 + 3] = sprite.center.dy - 5.0;
  ///     }
  ///     Paint paint = Paint();
  ///     canvas.drawRawAtlas(spriteAtlas, transformList, rectList, null, null, null, paint);
  ///   }
  ///
  ///   // ...
  /// }
  /// ```
  ///
  /// Another example usage which renders sprites with an optional opacity and rotation:
  ///
  /// ```dart
  /// class Sprite {
  ///   Sprite(this.index, this.center, this.alpha, this.rotation);
  ///   int index;
  ///   Offset center;
  ///   int alpha;
  ///   double rotation;
  /// }
  ///
  /// class MyPainter extends CustomPainter {
  ///   MyPainter(this.spriteAtlas, this.allSprites);
  ///
  ///   // assume spriteAtlas contains N 10x10 sprites side by side in a (N*10)x10 image
  ///   ui.Image spriteAtlas;
  ///   List<Sprite> allSprites;
  ///
  ///   @override
  ///   void paint(Canvas canvas, Size size) {
  ///     // For best advantage, these lists should be cached and only specific
  ///     // entries updated when the sprite information changes. This code is
  ///     // illustrative of how to set up the data and not a recommendation for
  ///     // optimal usage.
  ///     Float32List rectList = Float32List(allSprites.length * 4);
  ///     Float32List transformList = Float32List(allSprites.length * 4);
  ///     Int32List colorList = Int32List(allSprites.length);
  ///     for (int i = 0; i < allSprites.length; i++) {
  ///       Sprite sprite = allSprites[i];
  ///       final double rectX = sprite.index * 10.0;
  ///       rectList[i * 4 + 0] = rectX;
  ///       rectList[i * 4 + 1] = 0.0;
  ///       rectList[i * 4 + 2] = rectX + 10.0;
  ///       rectList[i * 4 + 3] = 10.0;
  ///
  ///       // This example uses an RSTransform object to compute the necessary values for
  ///       // the transform using a factory helper method because the sprites contain
  ///       // rotation values which are not trivial to work with. But if the math for the
  ///       // values falls out from other calculations on the sprites then the values could
  ///       // possibly be generated directly from the sprite update code.
  ///       final RSTransform transform = RSTransform.fromComponents(
  ///         rotation: sprite.rotation,
  ///         scale: 1.0,
  ///         // Center of the sprite relative to its rect
  ///         anchorX: 5.0,
  ///         anchorY: 5.0,
  ///         // Location at which to draw the center of the sprite
  ///         translateX: sprite.center.dx,
  ///         translateY: sprite.center.dy,
  ///       );
  ///       transformList[i * 4 + 0] = transform.scos;
  ///       transformList[i * 4 + 1] = transform.ssin;
  ///       transformList[i * 4 + 2] = transform.tx;
  ///       transformList[i * 4 + 3] = transform.ty;
  ///
  ///       // This example computes the color value directly, but one could also compute
  ///       // an actual Color object and use its Color.value getter for the same result.
  ///       // Since we are using BlendMode.srcIn, only the alpha component matters for
  ///       // these colors which makes this a simple shift operation.
  ///       colorList[i] = sprite.alpha << 24;
  ///     }
  ///     Paint paint = Paint();
  ///     canvas.drawRawAtlas(spriteAtlas, transformList, rectList, colorList, BlendMode.srcIn, null, paint);
  ///   }
  ///
  ///   // ...
  /// }
  /// ```
  ///
  /// See also:
  ///
  ///  * [drawAtlas], which takes its arguments as objects rather than typed
  ///    data lists.
  void drawRawAtlas(
    Image atlas,
    Float32List rstTransforms,
    Float32List rects,
    Int32List? colors,
    BlendMode? blendMode,
    Rect? cullRect,
    Paint paint,
  );

  /// Draws a shadow for a [Path] representing the given material elevation.
  ///
  /// The `transparentOccluder` argument should be true if the occluding object
  /// is not opaque.
  ///
  /// The arguments must not be null.
  void drawShadow(Path path, Color color, double elevation, bool transparentOccluder);
}

base class _NativeCanvas extends NativeFieldWrapperClass1 implements Canvas {
  _NativeCanvas(PictureRecorder recorder, [Rect? cullRect]) {
    if (recorder.isRecording) {
      throw ArgumentError('"recorder" must not already be associated with another Canvas.');
    }
    _recorder = recorder as _NativePictureRecorder;
    _recorder!._canvas = this;
    cullRect ??= Rect.largest;
    _constructor(_recorder!, cullRect.left, cullRect.top, cullRect.right, cullRect.bottom);
  }

  @Native<Void Function(Handle, Pointer<Void>, Double, Double, Double, Double)>(
    symbol: 'Canvas::Create',
  )
  external void _constructor(
    _NativePictureRecorder recorder,
    double left,
    double top,
    double right,
    double bottom,
  );

  // The underlying DlCanvas is owned by the DisplayListBuilder used to create this Canvas.
  // The Canvas holds a reference to the PictureRecorder to prevent the recorder from being
  // garbage collected until PictureRecorder.endRecording is called.
  _NativePictureRecorder? _recorder;

  @override
  @Native<Void Function(Pointer<Void>)>(symbol: 'Canvas::save', isLeaf: true)
  external void save();

  static Rect _sorted(Rect rect) {
    if (rect.isEmpty) {
      rect = Rect.fromLTRB(
        math.min(rect.left, rect.right),
        math.min(rect.top, rect.bottom),
        math.max(rect.left, rect.right),
        math.max(rect.top, rect.bottom),
      );
    }
    return rect;
  }

  @override
  void saveLayer(Rect? bounds, Paint paint) {
    if (bounds == null) {
      _saveLayerWithoutBounds(paint._objects, paint._data);
    } else {
      assert(_rectIsValid(bounds));
      _saveLayer(bounds.left, bounds.top, bounds.right, bounds.bottom, paint._objects, paint._data);
    }
  }

  @Native<Void Function(Pointer<Void>, Handle, Handle)>(symbol: 'Canvas::saveLayerWithoutBounds')
  external void _saveLayerWithoutBounds(List<Object?>? paintObjects, ByteData paintData);

  @Native<Void Function(Pointer<Void>, Double, Double, Double, Double, Handle, Handle)>(
    symbol: 'Canvas::saveLayer',
  )
  external void _saveLayer(
    double left,
    double top,
    double right,
    double bottom,
    List<Object?>? paintObjects,
    ByteData paintData,
  );

  @override
  @Native<Void Function(Pointer<Void>)>(symbol: 'Canvas::restore', isLeaf: true)
  external void restore();

  @override
  @Native<Void Function(Pointer<Void>, Int32)>(symbol: 'Canvas::restoreToCount', isLeaf: true)
  external void restoreToCount(int count);

  @override
  @Native<Int32 Function(Pointer<Void>)>(symbol: 'Canvas::getSaveCount', isLeaf: true)
  external int getSaveCount();

  @override
  @Native<Void Function(Pointer<Void>, Double, Double)>(symbol: 'Canvas::translate', isLeaf: true)
  external void translate(double dx, double dy);

  @override
  void scale(double sx, [double? sy]) => _scale(sx, sy ?? sx);

  @Native<Void Function(Pointer<Void>, Double, Double)>(symbol: 'Canvas::scale', isLeaf: true)
  external void _scale(double sx, double sy);

  @override
  @Native<Void Function(Pointer<Void>, Double)>(symbol: 'Canvas::rotate', isLeaf: true)
  external void rotate(double radians);

  @override
  @Native<Void Function(Pointer<Void>, Double, Double)>(symbol: 'Canvas::skew', isLeaf: true)
  external void skew(double sx, double sy);

  @override
  void transform(Float64List matrix4) {
    if (matrix4.length != 16) {
      throw ArgumentError('"matrix4" must have 16 entries.');
    }
    _transform(matrix4);
  }

  @Native<Void Function(Pointer<Void>, Handle)>(symbol: 'Canvas::transform')
  external void _transform(Float64List matrix4);

  @override
  Float64List getTransform() {
    final matrix4 = Float64List(16);
    _getTransform(matrix4);
    return matrix4;
  }

  @Native<Void Function(Pointer<Void>, Handle)>(symbol: 'Canvas::getTransform')
  external void _getTransform(Float64List matrix4);

  @override
  void clipRect(Rect rect, {ClipOp clipOp = ClipOp.intersect, bool doAntiAlias = true}) {
    assert(_rectIsValid(rect));
    rect = _sorted(rect);
    // Even if rect is still empty - which implies it has a zero dimension -
    // we still need to perform the clipRect operation as it will effectively
    // nullify any further rendering until the next restore call.
    _clipRect(rect.left, rect.top, rect.right, rect.bottom, clipOp.index, doAntiAlias);
  }

  @Native<Void Function(Pointer<Void>, Double, Double, Double, Double, Int32, Bool)>(
    symbol: 'Canvas::clipRect',
    isLeaf: true,
  )
  external void _clipRect(
    double left,
    double top,
    double right,
    double bottom,
    int clipOp,
    bool doAntiAlias,
  );

  @override
  void clipRRect(RRect rrect, {bool doAntiAlias = true}) {
    assert(_rrectIsValid(rrect));
    _clipRRect(rrect._getValue32(), doAntiAlias);
  }

  @Native<Void Function(Pointer<Void>, Handle, Bool)>(symbol: 'Canvas::clipRRect')
  external void _clipRRect(Float32List rrect, bool doAntiAlias);

  @override
  void clipRSuperellipse(RSuperellipse rsuperellipse, {bool doAntiAlias = true}) {
    assert(_rsuperellipseIsValid(rsuperellipse));
    _clipRSuperellipse(rsuperellipse._native(), doAntiAlias);
  }

  @Native<Void Function(Pointer<Void>, Pointer<Void>, Bool)>(symbol: 'Canvas::clipRSuperellipse')
  external void _clipRSuperellipse(_NativeRSuperellipse rsuperellipse, bool doAntiAlias);

  @override
  void clipPath(Path path, {bool doAntiAlias = true}) {
    _clipPath(path as _NativePath, doAntiAlias);
  }

  @Native<Void Function(Pointer<Void>, Pointer<Void>, Bool)>(symbol: 'Canvas::clipPath')
  external void _clipPath(_NativePath path, bool doAntiAlias);

  @override
  Rect getLocalClipBounds() {
    final bounds = Float64List(4);
    _getLocalClipBounds(bounds);
    return Rect.fromLTRB(bounds[0], bounds[1], bounds[2], bounds[3]);
  }

  @Native<Void Function(Pointer<Void>, Handle)>(symbol: 'Canvas::getLocalClipBounds')
  external void _getLocalClipBounds(Float64List bounds);

  @override
  Rect getDestinationClipBounds() {
    final bounds = Float64List(4);
    _getDestinationClipBounds(bounds);
    return Rect.fromLTRB(bounds[0], bounds[1], bounds[2], bounds[3]);
  }

  @Native<Void Function(Pointer<Void>, Handle)>(symbol: 'Canvas::getDestinationClipBounds')
  external void _getDestinationClipBounds(Float64List bounds);

  @override
  void drawColor(Color color, BlendMode blendMode) {
    _drawColor(color.value, blendMode.index);
  }

  @Native<Void Function(Pointer<Void>, Uint32, Int32)>(symbol: 'Canvas::drawColor', isLeaf: true)
  external void _drawColor(int color, int blendMode);

  @override
  void drawLine(Offset p1, Offset p2, Paint paint) {
    assert(_offsetIsValid(p1));
    assert(_offsetIsValid(p2));
    _drawLine(p1.dx, p1.dy, p2.dx, p2.dy, paint._objects, paint._data);
  }

  @Native<Void Function(Pointer<Void>, Double, Double, Double, Double, Handle, Handle)>(
    symbol: 'Canvas::drawLine',
  )
  external void _drawLine(
    double x1,
    double y1,
    double x2,
    double y2,
    List<Object?>? paintObjects,
    ByteData paintData,
  );

  @override
  void drawPaint(Paint paint) {
    _drawPaint(paint._objects, paint._data);
  }

  @Native<Void Function(Pointer<Void>, Handle, Handle)>(symbol: 'Canvas::drawPaint')
  external void _drawPaint(List<Object?>? paintObjects, ByteData paintData);

  @override
  void drawRect(Rect rect, Paint paint) {
    assert(_rectIsValid(rect));
    rect = _sorted(rect);
    if (paint.style != PaintingStyle.fill || !rect.isEmpty) {
      _drawRect(rect.left, rect.top, rect.right, rect.bottom, paint._objects, paint._data);
    }
  }

  @Native<Void Function(Pointer<Void>, Double, Double, Double, Double, Handle, Handle)>(
    symbol: 'Canvas::drawRect',
  )
  external void _drawRect(
    double left,
    double top,
    double right,
    double bottom,
    List<Object?>? paintObjects,
    ByteData paintData,
  );

  @override
  void drawRRect(RRect rrect, Paint paint) {
    assert(_rrectIsValid(rrect));
    _drawRRect(rrect._getValue32(), paint._objects, paint._data);
  }

  @Native<Void Function(Pointer<Void>, Handle, Handle, Handle)>(symbol: 'Canvas::drawRRect')
  external void _drawRRect(Float32List rrect, List<Object?>? paintObjects, ByteData paintData);

  @override
  void drawDRRect(RRect outer, RRect inner, Paint paint) {
    assert(_rrectIsValid(outer));
    assert(_rrectIsValid(inner));
    _drawDRRect(outer._getValue32(), inner._getValue32(), paint._objects, paint._data);
  }

  @Native<Void Function(Pointer<Void>, Handle, Handle, Handle, Handle)>(
    symbol: 'Canvas::drawDRRect',
  )
  external void _drawDRRect(
    Float32List outer,
    Float32List inner,
    List<Object?>? paintObjects,
    ByteData paintData,
  );

  @override
  void drawRSuperellipse(RSuperellipse rsuperellipse, Paint paint) {
    assert(_rsuperellipseIsValid(rsuperellipse));
    _drawRSuperellipse(rsuperellipse._native(), paint._objects, paint._data);
  }

  @Native<Void Function(Pointer<Void>, Pointer<Void>, Handle, Handle)>(
    symbol: 'Canvas::drawRSuperellipse',
  )
  external void _drawRSuperellipse(
    _NativeRSuperellipse rsuperellipse,
    List<Object?>? paintObjects,
    ByteData paintData,
  );

  @override
  void drawOval(Rect rect, Paint paint) {
    assert(_rectIsValid(rect));
    rect = _sorted(rect);
    if (paint.style != PaintingStyle.fill || !rect.isEmpty) {
      _drawOval(rect.left, rect.top, rect.right, rect.bottom, paint._objects, paint._data);
    }
  }

  @Native<Void Function(Pointer<Void>, Double, Double, Double, Double, Handle, Handle)>(
    symbol: 'Canvas::drawOval',
  )
  external void _drawOval(
    double left,
    double top,
    double right,
    double bottom,
    List<Object?>? paintObjects,
    ByteData paintData,
  );

  @override
  void drawCircle(Offset c, double radius, Paint paint) {
    assert(_offsetIsValid(c));
    _drawCircle(c.dx, c.dy, radius, paint._objects, paint._data);
  }

  @Native<Void Function(Pointer<Void>, Double, Double, Double, Handle, Handle)>(
    symbol: 'Canvas::drawCircle',
  )
  external void _drawCircle(
    double x,
    double y,
    double radius,
    List<Object?>? paintObjects,
    ByteData paintData,
  );

  @override
  void drawArc(Rect rect, double startAngle, double sweepAngle, bool useCenter, Paint paint) {
    assert(_rectIsValid(rect));
    _drawArc(
      rect.left,
      rect.top,
      rect.right,
      rect.bottom,
      startAngle,
      sweepAngle,
      useCenter,
      paint._objects,
      paint._data,
    );
  }

  @Native<
    Void Function(
      Pointer<Void>,
      Double,
      Double,
      Double,
      Double,
      Double,
      Double,
      Bool,
      Handle,
      Handle,
    )
  >(symbol: 'Canvas::drawArc')
  external void _drawArc(
    double left,
    double top,
    double right,
    double bottom,
    double startAngle,
    double sweepAngle,
    bool useCenter,
    List<Object?>? paintObjects,
    ByteData paintData,
  );

  @override
  void drawPath(Path path, Paint paint) {
    _drawPath(path as _NativePath, paint._objects, paint._data);
  }

  @Native<Void Function(Pointer<Void>, Pointer<Void>, Handle, Handle)>(symbol: 'Canvas::drawPath')
  external void _drawPath(_NativePath path, List<Object?>? paintObjects, ByteData paintData);

  @override
  void drawImage(Image image, Offset offset, Paint paint) {
    assert(!image.debugDisposed);
    assert(_offsetIsValid(offset));
    final String? error = _drawImage(
      image._image,
      offset.dx,
      offset.dy,
      paint._objects,
      paint._data,
      paint.filterQuality.index,
    );
    if (error != null) {
      throw PictureRasterizationException._(error, stack: image._debugStack);
    }
  }

  @Native<Handle Function(Pointer<Void>, Pointer<Void>, Double, Double, Handle, Handle, Int32)>(
    symbol: 'Canvas::drawImage',
  )
  external String? _drawImage(
    _Image image,
    double x,
    double y,
    List<Object?>? paintObjects,
    ByteData paintData,
    int filterQualityIndex,
  );

  @override
  void drawImageRect(Image image, Rect src, Rect dst, Paint paint) {
    assert(!image.debugDisposed);
    assert(_rectIsValid(src));
    assert(_rectIsValid(dst));
    final String? error = _drawImageRect(
      image._image,
      src.left,
      src.top,
      src.right,
      src.bottom,
      dst.left,
      dst.top,
      dst.right,
      dst.bottom,
      paint._objects,
      paint._data,
      paint.filterQuality.index,
    );
    if (error != null) {
      throw PictureRasterizationException._(error, stack: image._debugStack);
    }
  }

  @Native<
    Handle Function(
      Pointer<Void>,
      Pointer<Void>,
      Double,
      Double,
      Double,
      Double,
      Double,
      Double,
      Double,
      Double,
      Handle,
      Handle,
      Int32,
    )
  >(symbol: 'Canvas::drawImageRect')
  external String? _drawImageRect(
    _Image image,
    double srcLeft,
    double srcTop,
    double srcRight,
    double srcBottom,
    double dstLeft,
    double dstTop,
    double dstRight,
    double dstBottom,
    List<Object?>? paintObjects,
    ByteData paintData,
    int filterQualityIndex,
  );

  @override
  void drawImageNine(Image image, Rect center, Rect dst, Paint paint) {
    assert(!image.debugDisposed);
    assert(_rectIsValid(center));
    assert(_rectIsValid(dst));
    final String? error = _drawImageNine(
      image._image,
      center.left,
      center.top,
      center.right,
      center.bottom,
      dst.left,
      dst.top,
      dst.right,
      dst.bottom,
      paint._objects,
      paint._data,
      paint.filterQuality.index,
    );
    if (error != null) {
      throw PictureRasterizationException._(error, stack: image._debugStack);
    }
  }

  @Native<
    Handle Function(
      Pointer<Void>,
      Pointer<Void>,
      Double,
      Double,
      Double,
      Double,
      Double,
      Double,
      Double,
      Double,
      Handle,
      Handle,
      Int32,
    )
  >(symbol: 'Canvas::drawImageNine')
  external String? _drawImageNine(
    _Image image,
    double centerLeft,
    double centerTop,
    double centerRight,
    double centerBottom,
    double dstLeft,
    double dstTop,
    double dstRight,
    double dstBottom,
    List<Object?>? paintObjects,
    ByteData paintData,
    int filterQualityIndex,
  );

  @override
  void drawPicture(Picture picture) {
    assert(!picture.debugDisposed);
    _drawPicture(picture as _NativePicture);
  }

  @Native<Void Function(Pointer<Void>, Pointer<Void>)>(symbol: 'Canvas::drawPicture')
  external void _drawPicture(_NativePicture picture);

  @override
  void drawParagraph(Paragraph paragraph, Offset offset) {
    final nativeParagraph = paragraph as _NativeParagraph;
    assert(!nativeParagraph.debugDisposed);
    assert(_offsetIsValid(offset));
    assert(!nativeParagraph._needsLayout);
    nativeParagraph._paint(this, offset.dx, offset.dy);
  }

  @override
  void drawPoints(PointMode pointMode, List<Offset> points, Paint paint) {
    _drawPoints(paint._objects, paint._data, pointMode.index, _encodePointList(points));
  }

  @override
  void drawRawPoints(PointMode pointMode, Float32List points, Paint paint) {
    if (points.length % 2 != 0) {
      throw ArgumentError('"points" must have an even number of values.');
    }
    _drawPoints(paint._objects, paint._data, pointMode.index, points);
  }

  @Native<Void Function(Pointer<Void>, Handle, Handle, Int32, Handle)>(symbol: 'Canvas::drawPoints')
  external void _drawPoints(
    List<Object?>? paintObjects,
    ByteData paintData,
    int pointMode,
    Float32List points,
  );

  @override
  void drawVertices(Vertices vertices, BlendMode blendMode, Paint paint) {
    assert(!vertices.debugDisposed);
    _drawVertices(vertices, blendMode.index, paint._objects, paint._data);
  }

  @Native<Void Function(Pointer<Void>, Pointer<Void>, Int32, Handle, Handle)>(
    symbol: 'Canvas::drawVertices',
  )
  external void _drawVertices(
    Vertices vertices,
    int blendMode,
    List<Object?>? paintObjects,
    ByteData paintData,
  );

  @override
  void drawAtlas(
    Image atlas,
    List<RSTransform> transforms,
    List<Rect> rects,
    List<Color>? colors,
    BlendMode? blendMode,
    Rect? cullRect,
    Paint paint,
  ) {
    assert(!atlas.debugDisposed);
    assert(colors == null || colors.isEmpty || blendMode != null);

    final int rectCount = rects.length;
    if (transforms.length != rectCount) {
      throw ArgumentError('"transforms" and "rects" lengths must match.');
    }
    if (colors != null && colors.isNotEmpty && colors.length != rectCount) {
      throw ArgumentError(
        'If non-null, "colors" length must match that of "transforms" and "rects".',
      );
    }

    final rstTransformBuffer = Float32List(rectCount * 4);
    final rectBuffer = Float32List(rectCount * 4);

    for (var i = 0; i < rectCount; i++) {
      final int index0 = i * 4;
      final int index1 = index0 + 1;
      final int index2 = index0 + 2;
      final int index3 = index0 + 3;
      final RSTransform rstTransform = transforms[i];
      final Rect rect = rects[i];
      assert(_rectIsValid(rect));
      rstTransformBuffer[index0] = rstTransform.scos;
      rstTransformBuffer[index1] = rstTransform.ssin;
      rstTransformBuffer[index2] = rstTransform.tx;
      rstTransformBuffer[index3] = rstTransform.ty;
      rectBuffer[index0] = rect.left;
      rectBuffer[index1] = rect.top;
      rectBuffer[index2] = rect.right;
      rectBuffer[index3] = rect.bottom;
    }

    final Int32List? colorBuffer = (colors == null || colors.isEmpty)
        ? null
        : _encodeColorList(colors);
    final Float32List? cullRectBuffer = cullRect?._getValue32();
    final int qualityIndex = paint.filterQuality.index;

    final String? error = _drawAtlas(
      paint._objects,
      paint._data,
      qualityIndex,
      atlas._image,
      rstTransformBuffer,
      rectBuffer,
      colorBuffer,
      (blendMode ?? BlendMode.src).index,
      cullRectBuffer,
    );

    if (error != null) {
      throw PictureRasterizationException._(error, stack: atlas._debugStack);
    }
  }

  @override
  void drawRawAtlas(
    Image atlas,
    Float32List rstTransforms,
    Float32List rects,
    Int32List? colors,
    BlendMode? blendMode,
    Rect? cullRect,
    Paint paint,
  ) {
    assert(colors == null || blendMode != null);

    final int rectCount = rects.length;
    if (rstTransforms.length != rectCount) {
      throw ArgumentError('"rstTransforms" and "rects" lengths must match.');
    }
    if (rectCount % 4 != 0) {
      throw ArgumentError('"rstTransforms" and "rects" lengths must be a multiple of four.');
    }
    if (colors != null && colors.length * 4 != rectCount) {
      throw ArgumentError(
        'If non-null, "colors" length must be one fourth the length of "rstTransforms" and "rects".',
      );
    }
    final int qualityIndex = paint.filterQuality.index;

    final String? error = _drawAtlas(
      paint._objects,
      paint._data,
      qualityIndex,
      atlas._image,
      rstTransforms,
      rects,
      colors,
      (blendMode ?? BlendMode.src).index,
      cullRect?._getValue32(),
    );

    if (error != null) {
      throw PictureRasterizationException._(error, stack: atlas._debugStack);
    }
  }

  @Native<
    Handle Function(
      Pointer<Void>,
      Handle,
      Handle,
      Int32,
      Pointer<Void>,
      Handle,
      Handle,
      Handle,
      Int32,
      Handle,
    )
  >(symbol: 'Canvas::drawAtlas')
  external String? _drawAtlas(
    List<Object?>? paintObjects,
    ByteData paintData,
    int filterQualityIndex,
    _Image atlas,
    Float32List rstTransforms,
    Float32List rects,
    Int32List? colors,
    int blendMode,
    Float32List? cullRect,
  );

  @override
  void drawShadow(Path path, Color color, double elevation, bool transparentOccluder) {
    _drawShadow(path as _NativePath, color.value, elevation, transparentOccluder);
  }

  @Native<Void Function(Pointer<Void>, Pointer<Void>, Uint32, Double, Bool)>(
    symbol: 'Canvas::drawShadow',
  )
  external void _drawShadow(
    _NativePath path,
    int color,
    double elevation,
    bool transparentOccluder,
  );

  @override
  String toString() => 'Canvas(recording: ${_recorder != null})';
}

/// Signature for [Picture] lifecycle events.
typedef PictureEventCallback = void Function(Picture picture);

/// An object representing a sequence of recorded graphical operations.
///
/// To create a [Picture], use a [PictureRecorder].
///
/// A [Picture] can be placed in a [Scene] using a [SceneBuilder], via
/// the [SceneBuilder.addPicture] method. A [Picture] can also be
/// drawn into a [Canvas], using the [Canvas.drawPicture] method.
abstract class Picture {
  /// A callback that is invoked to report a picture creation.
  ///
  /// It's preferred to use [MemoryAllocations] in flutter/foundation.dart
  /// than to use [onCreate] directly because [MemoryAllocations]
  /// allows multiple callbacks.
  static PictureEventCallback? onCreate;

  /// A callback that is invoked to report the picture disposal.
  ///
  /// It's preferred to use [MemoryAllocations] in flutter/foundation.dart
  /// than to use [onDispose] directly because [MemoryAllocations]
  /// allows multiple callbacks.
  static PictureEventCallback? onDispose;

  /// Creates an image from this picture.
  ///
  /// The returned image will be `width` pixels wide and `height` pixels high.
  /// The picture is rasterized within the 0 (left), 0 (top), `width` (right),
  /// `height` (bottom) bounds. Content outside these bounds is clipped.
  Future<Image> toImage(int width, int height);

  /// Synchronously creates a handle to an image of this picture.
  ///
  /// {@template dart.ui.painting.Picture.toImageSync}
  /// The returned image will be [width] pixels wide and [height] pixels high.
  /// The picture is rasterized within the 0 (left), 0 (top), [width] (right),
  /// [height] (bottom) bounds. Content outside these bounds is clipped.
  ///
  /// The image object is created and returned synchronously, but is rasterized
  /// asynchronously. If the rasterization fails, an exception will be thrown
  /// when the image is drawn to a [Canvas].
  ///
  /// If a GPU context is available, this image will be created as GPU resident
  /// and not copied back to the host. This means the image will be more
  /// efficient to draw.
  ///
  /// If no GPU context is available, the image will be rasterized on the CPU.
  ///
  /// The [targetFormat] argument specifies the pixel format of the returned
  /// [Image]. If [TargetPixelFormat.dontCare] is specified, the pixel format
  /// will be chosen automatically based on the GPU capabilities.
  /// {@endtemplate}
  Image toImageSync(
    int width,
    int height, {
    TargetPixelFormat targetFormat = TargetPixelFormat.dontCare,
  });

  /// Release the resources used by this object. The object is no longer usable
  /// after this method is called.
  void dispose();

  /// Whether this reference to the underlying picture is [dispose]d.
  ///
  /// This only returns a valid value if asserts are enabled, and must not be
  /// used otherwise.
  bool get debugDisposed;

  /// Returns the approximate number of bytes allocated for this object.
  ///
  /// The actual size of this picture may be larger, particularly if it contains
  /// references to image or other large objects.
  int get approximateBytesUsed;
}

base class _NativePicture extends NativeFieldWrapperClass1 implements Picture {
  /// This class is created by the engine, and should not be instantiated
  /// or extended directly.
  ///
  /// To create a [Picture], use a [PictureRecorder].
  _NativePicture._();

  @override
  Future<Image> toImage(int width, int height) {
    assert(!_disposed);
    if (width <= 0 || height <= 0) {
      throw Exception('Invalid image dimensions.');
    }
    return _futurize(
      (_Callback<Image?> callback) => _toImage(width, height, (_Image? image) {
        if (image == null) {
          callback(null);
        } else {
          callback(Image._(image, image.width, image.height));
        }
      }),
    );
  }

  @Native<Handle Function(Pointer<Void>, Uint32, Uint32, Handle)>(symbol: 'Picture::toImage')
  external String? _toImage(int width, int height, void Function(_Image?) callback);

  @override
  Image toImageSync(
    int width,
    int height, {
    TargetPixelFormat targetFormat = TargetPixelFormat.dontCare,
  }) {
    assert(!_disposed);
    if (width <= 0 || height <= 0) {
      throw Exception('Invalid image dimensions.');
    }

    final image = _Image._();
    _toImageSync(width, height, targetFormat.index, image);
    return Image._(image, image.width, image.height);
  }

  @Native<Void Function(Pointer<Void>, Uint32, Uint32, Int32, Handle)>(
    symbol: 'Picture::toImageSync',
  )
  external void _toImageSync(int width, int height, int targetFormat, _Image outImage);

  @override
  void dispose() {
    assert(!_disposed);
    assert(() {
      _disposed = true;
      return true;
    }());
    Picture.onDispose?.call(this);
    _dispose();
  }

  /// This can't be a leaf call because the native function calls Dart API
  /// (Dart_SetNativeInstanceField).
  @Native<Void Function(Pointer<Void>)>(symbol: 'Picture::dispose')
  external void _dispose();

  bool _disposed = false;

  @override
  bool get debugDisposed {
    bool? disposed;
    assert(() {
      disposed = _disposed;
      return true;
    }());
    return disposed ??
        (throw StateError('Picture.debugDisposed is only available when asserts are enabled.'));
  }

  @override
  @Native<Uint64 Function(Pointer<Void>)>(symbol: 'Picture::GetAllocationSize', isLeaf: true)
  external int get approximateBytesUsed;

  @override
  String toString() => 'Picture';
}

/// Records a [Picture] containing a sequence of graphical operations.
///
/// To begin recording, construct a [Canvas] to record the commands.
/// To end recording, use the [PictureRecorder.endRecording] method.
///
/// ## Use with the Flutter framework
///
/// The Flutter framework's [RendererBinding] provides a hook for creating
/// [PictureRecorder] objects ([RendererBinding.createPictureRecorder]) that
/// allows tests to hook into the scene creation logic. When creating a
/// [PictureRecorder] and [Canvas] that will be used with a [PictureLayer] as
/// part of the [Scene] in the context of the Flutter framework, consider
/// calling [RendererBinding.createPictureRecorder] instead of calling the
/// [PictureRecorder.new] constructor directly.
///
/// This does not apply when using a canvas to generate a bitmap for other
/// purposes, e.g. for generating a PNG image using [Picture.toImage].
abstract class PictureRecorder {
  /// Creates a new idle PictureRecorder. To associate it with a
  /// [Canvas] and begin recording, pass this [PictureRecorder] to the
  /// [Canvas] constructor.
  factory PictureRecorder() = _NativePictureRecorder;

  /// Whether this object is currently recording commands.
  ///
  /// Specifically, this returns true if a [Canvas] object has been
  /// created to record commands and recording has not yet ended via a
  /// call to [endRecording], and false if either this
  /// [PictureRecorder] has not yet been associated with a [Canvas],
  /// or the [endRecording] method has already been called.
  bool get isRecording;

  /// Finishes recording graphical operations.
  ///
  /// Returns a picture containing the graphical operations that have been
  /// recorded thus far. After calling this function, both the picture recorder
  /// and the canvas objects are invalid and cannot be used further.
  Picture endRecording();
}

base class _NativePictureRecorder extends NativeFieldWrapperClass1 implements PictureRecorder {
  _NativePictureRecorder() {
    _constructor();
  }

  @Native<Void Function(Handle)>(symbol: 'PictureRecorder::Create')
  external void _constructor();

  @override
  bool get isRecording => _canvas != null;

  @override
  Picture endRecording() {
    if (_canvas == null) {
      throw StateError('PictureRecorder did not start recording.');
    }
    final picture = _NativePicture._();
    _endRecording(picture);
    _canvas!._recorder = null;
    _canvas = null;
    // We invoke the handler here, not in the Picture constructor, because we want
    // [picture.approximateBytesUsed] to be available for the handler.
    Picture.onCreate?.call(picture);
    return picture;
  }

  @Native<Void Function(Pointer<Void>, Handle)>(symbol: 'PictureRecorder::endRecording')
  external void _endRecording(_NativePicture outPicture);

  _NativeCanvas? _canvas;

  @override
  String toString() => 'PictureRecorder(recording: $isRecording)';
}

/// A single shadow.
///
/// Multiple shadows are stacked together in a [TextStyle].
class Shadow {
  /// Construct a shadow.
  ///
  /// The default shadow is a black shadow with zero offset and zero blur.
  /// Default shadows should be completely covered by the casting element,
  /// and not be visible.
  ///
  /// Transparency should be adjusted through the [color] alpha.
  ///
  /// Shadow order matters due to compositing multiple translucent objects not
  /// being commutative.
  const Shadow({
    this.color = const Color(_kColorDefault),
    this.offset = Offset.zero,
    this.blurRadius = 0.0,
  }) : assert(blurRadius >= 0.0, 'Text shadow blur radius should be non-negative.');

  static const int _kColorDefault = 0xFF000000;
  // Constants for shadow encoding.
  static const int _kBytesPerShadow = 16;
  static const int _kColorOffset = 0 << 2;
  static const int _kXOffset = 1 << 2;
  static const int _kYOffset = 2 << 2;
  static const int _kBlurOffset = 3 << 2;

  /// Color that the shadow will be drawn with.
  ///
  /// The shadows are shapes composited directly over the base canvas, and do not
  /// represent optical occlusion.
  final Color color;

  /// The displacement of the shadow from the casting element.
  ///
  /// Positive x/y offsets will shift the shadow to the right and down, while
  /// negative offsets shift the shadow to the left and up. The offsets are
  /// relative to the position of the element that is casting it.
  final Offset offset;

  /// The standard deviation of the Gaussian to convolve with the shadow's shape.
  final double blurRadius;

  /// Converts a blur radius in pixels to sigmas.
  ///
  /// See the sigma argument to [MaskFilter.blur].
  ///
  // See SkBlurMask::ConvertRadiusToSigma().
  // <https://github.com/google/skia/blob/bb5b77db51d2e149ee66db284903572a5aac09be/src/effects/SkBlurMask.cpp#L23>
  static double convertRadiusToSigma(double radius) {
    return radius > 0 ? radius * 0.57735 + 0.5 : 0;
  }

  /// The [blurRadius] in sigmas instead of logical pixels.
  ///
  /// See the sigma argument to [MaskFilter.blur].
  double get blurSigma => convertRadiusToSigma(blurRadius);

  /// Create the [Paint] object that corresponds to this shadow description.
  ///
  /// The [offset] is not represented in the [Paint] object.
  /// To honor this as well, the shape should be translated by [offset] before
  /// being filled using this [Paint].
  ///
  /// This class does not provide a way to disable shadows to avoid
  /// inconsistencies in shadow blur rendering, primarily as a method of
  /// reducing test flakiness. [toPaint] should be overridden in subclasses to
  /// provide this functionality.
  Paint toPaint() {
    return Paint()
      ..color = color
      ..maskFilter = MaskFilter.blur(BlurStyle.normal, blurSigma);
  }

  /// Returns a new shadow with its [offset] and [blurRadius] scaled by the given
  /// factor.
  Shadow scale(double factor) {
    return Shadow(color: color, offset: offset * factor, blurRadius: blurRadius * factor);
  }

  /// Linearly interpolate between two shadows.
  ///
  /// If either shadow is null, this function linearly interpolates from
  /// a shadow that matches the other shadow in color but has a zero
  /// offset and a zero blurRadius.
  ///
  /// {@template dart.ui.shadow.lerp}
  /// The `t` argument represents position on the timeline, with 0.0 meaning
  /// that the interpolation has not started, returning `a` (or something
  /// equivalent to `a`), 1.0 meaning that the interpolation has finished,
  /// returning `b` (or something equivalent to `b`), and values in between
  /// meaning that the interpolation is at the relevant point on the timeline
  /// between `a` and `b`. The interpolation can be extrapolated beyond 0.0 and
  /// 1.0, so negative values and values greater than 1.0 are valid (and can
  /// easily be generated by curves such as [Curves.elasticInOut]).
  ///
  /// Values for `t` are usually obtained from an [Animation<double>], such as
  /// an [AnimationController].
  /// {@endtemplate}
  static Shadow? lerp(Shadow? a, Shadow? b, double t) {
    if (b == null) {
      if (a == null) {
        return null;
      } else {
        return a.scale(1.0 - t);
      }
    } else {
      if (a == null) {
        return b.scale(t);
      } else {
        return Shadow(
          color: Color.lerp(a.color, b.color, t)!,
          offset: Offset.lerp(a.offset, b.offset, t)!,
          blurRadius: _lerpDouble(a.blurRadius, b.blurRadius, t),
        );
      }
    }
  }

  /// Linearly interpolate between two lists of shadows.
  ///
  /// If the lists differ in length, excess items are lerped with null.
  ///
  /// {@macro dart.ui.shadow.lerp}
  static List<Shadow>? lerpList(List<Shadow>? a, List<Shadow>? b, double t) {
    if (a == null && b == null) {
      return null;
    }
    a ??= <Shadow>[];
    b ??= <Shadow>[];
    final result = <Shadow>[];
    final int commonLength = math.min(a.length, b.length);
    for (var i = 0; i < commonLength; i += 1) {
      result.add(Shadow.lerp(a[i], b[i], t)!);
    }
    for (var i = commonLength; i < a.length; i += 1) {
      result.add(a[i].scale(1.0 - t));
    }
    for (var i = commonLength; i < b.length; i += 1) {
      result.add(b[i].scale(t));
    }
    return result;
  }

  @override
  bool operator ==(Object other) {
    if (identical(this, other)) {
      return true;
    }
    return other is Shadow &&
        other.color == color &&
        other.offset == offset &&
        other.blurRadius == blurRadius;
  }

  @override
  int get hashCode => Object.hash(color, offset, blurRadius);

  // Serialize [shadows] into ByteData. The format is a single uint_32_t at
  // the beginning indicating the number of shadows, followed by _kBytesPerShadow
  // bytes for each shadow.
  static ByteData _encodeShadows(List<Shadow>? shadows) {
    if (shadows == null) {
      return ByteData(0);
    }

    final int byteCount = shadows.length * _kBytesPerShadow;
    final shadowsData = ByteData(byteCount);

    var shadowOffset = 0;
    for (var shadowIndex = 0; shadowIndex < shadows.length; ++shadowIndex) {
      final Shadow shadow = shadows[shadowIndex];
      shadowOffset = shadowIndex * _kBytesPerShadow;

      shadowsData.setInt32(
        _kColorOffset + shadowOffset,
        shadow.color.value ^ Shadow._kColorDefault,
        _kFakeHostEndian,
      );

      shadowsData.setFloat32(_kXOffset + shadowOffset, shadow.offset.dx, _kFakeHostEndian);

      shadowsData.setFloat32(_kYOffset + shadowOffset, shadow.offset.dy, _kFakeHostEndian);

      final double blurSigma = Shadow.convertRadiusToSigma(shadow.blurRadius);
      shadowsData.setFloat32(_kBlurOffset + shadowOffset, blurSigma, _kFakeHostEndian);
    }

    return shadowsData;
  }

  @override
  String toString() => 'TextShadow($color, $offset, $blurRadius)';
}

/// A handle to a read-only byte buffer that is managed by the engine.
///
/// The creator of this object is responsible for calling [dispose] when it is
/// no longer needed.
base class ImmutableBuffer extends NativeFieldWrapperClass1 {
  ImmutableBuffer._(this._length);

  /// Creates a copy of the data from a [Uint8List] suitable for internal use
  /// in the engine.
  static Future<ImmutableBuffer> fromUint8List(Uint8List list) {
    final instance = ImmutableBuffer._(list.length);
    return _futurize((_Callback<void> callback) {
      return instance._init(list, callback);
    }).then((_) => instance);
  }

  /// Create a buffer from the asset with key [assetKey].
  ///
  /// Throws an [Exception] if the asset does not exist.
  static Future<ImmutableBuffer> fromAsset(String assetKey) {
    // The flutter tool converts all asset keys with spaces into URI
    // encoded paths (replacing ' ' with '%20', for example). We perform
    // the same encoding here so that users can load assets with the same
    // key they have written in the pubspec.
    final String encodedKey = Uri(path: Uri.encodeFull(assetKey)).path;
    final instance = ImmutableBuffer._(0);
    return _futurize((_Callback<int> callback) {
      return instance._initFromAsset(encodedKey, callback);
    }).then((int length) {
      if (length == -1) {
        throw Exception('Asset not found');
      }
      return instance.._length = length;
    });
  }

  /// Create a buffer from the file with [path].
  ///
  /// Throws an [Exception] if the asset does not exist.
  static Future<ImmutableBuffer> fromFilePath(String path) {
    final instance = ImmutableBuffer._(0);
    return _futurize((_Callback<int> callback) {
      return instance._initFromFile(path, callback);
    }).then((int length) {
      if (length == -1) {
        throw Exception('Could not load file at $path.');
      }
      return instance.._length = length;
    });
  }

  @Native<Handle Function(Handle, Handle, Handle)>(symbol: 'ImmutableBuffer::init')
  external String? _init(Uint8List list, _Callback<void> callback);

  @Native<Handle Function(Handle, Handle, Handle)>(symbol: 'ImmutableBuffer::initFromAsset')
  external String? _initFromAsset(String assetKey, _Callback<int> callback);

  @Native<Handle Function(Handle, Handle, Handle)>(symbol: 'ImmutableBuffer::initFromFile')
  external String? _initFromFile(String assetKey, _Callback<int> callback);

  /// The length, in bytes, of the underlying data.
  int get length => _length;
  int _length;

  bool _debugDisposed = false;

  /// Whether [dispose] has been called.
  ///
  /// This must only be used when asserts are enabled. Otherwise, it will throw.
  bool get debugDisposed {
    late bool disposed;
    assert(() {
      disposed = _debugDisposed;
      return true;
    }());
    return disposed;
  }

  /// Release the resources used by this object. The object is no longer usable
  /// after this method is called.
  ///
  /// The underlying memory allocated by this object will be retained beyond
  /// this call if it is still needed by another object that has not been
  /// disposed. For example, an [ImageDescriptor] that has not been disposed
  /// may still retain a reference to the memory from this buffer even if it
  /// has been disposed. Freeing that memory requires disposing all resources
  /// that may still hold it.
  void dispose() {
    assert(() {
      assert(!_debugDisposed);
      _debugDisposed = true;
      return true;
    }());
    _dispose();
  }

  /// This can't be a leaf call because the native function calls Dart API
  /// (Dart_SetNativeInstanceField).
  @Native<Void Function(Pointer<Void>)>(symbol: 'ImmutableBuffer::dispose')
  external void _dispose();
}

/// A descriptor of data that can be turned into an [Image] via a [Codec].
///
/// Use this class to determine the height, width, and byte size of image data
/// before decoding it.
abstract class ImageDescriptor {
  /// Creates an image descriptor from raw image pixels.
  ///
  /// The `pixels` parameter is the pixel data. They are packed in bytes in the
  /// order described by `pixelFormat`, then grouped in rows, from left to right,
  /// then top to bottom.
  ///
  /// The `rowBytes` parameter is the number of bytes consumed by each row of
  /// pixels in the data buffer. If unspecified, it defaults to `width` multiplied
  /// by the number of bytes per pixel in the provided `format`.
  // Not async because there's no expensive work to do here.
  factory ImageDescriptor.raw(
    ImmutableBuffer buffer, {
    required int width,
    required int height,
    int? rowBytes,
    required PixelFormat pixelFormat,
  }) = _NativeImageDescriptor.raw;

  /// Creates an image descriptor from encoded data in a supported format.
  static Future<ImageDescriptor> encoded(ImmutableBuffer buffer) {
    final descriptor = _NativeImageDescriptor._();
    return _futurize((_Callback<void> callback) {
      return descriptor._initEncoded(buffer, callback);
    }).then((_) => descriptor);
  }

  /// The width, in pixels, of the image.
  ///
  /// On the Web, this is only supported for [raw] images.
  int get width;

  /// The height, in pixels, of the image.
  ///
  /// On the Web, this is only supported for [raw] images.
  int get height;

  /// The number of bytes per pixel in the image.
  ///
  /// On web, this is only supported for [raw] images.
  int get bytesPerPixel;

  /// Release the resources used by this object. The object is no longer usable
  /// after this method is called.
  ///
  /// This can't be a leaf call because the native function calls Dart API
  /// (Dart_SetNativeInstanceField).
  void dispose();

  /// Creates a [Codec] object which is suitable for decoding the data in the
  /// buffer to an [Image].
  ///
  /// If only one of targetWidth or  targetHeight are specified, the other
  /// dimension will be scaled according to the aspect ratio of the supplied
  /// dimension.
  ///
  /// If either targetWidth or targetHeight is less than or equal to zero, it
  /// will be treated as if it is null.
  Future<Codec> instantiateCodec({
    int? targetWidth,
    int? targetHeight,
    TargetPixelFormat targetFormat = TargetPixelFormat.dontCare,
  });
}

base class _NativeImageDescriptor extends NativeFieldWrapperClass1 implements ImageDescriptor {
  _NativeImageDescriptor._();

  /// Creates an image descriptor from raw image pixels.
  ///
  /// The `pixels` parameter is the pixel data. They are packed in bytes in the
  /// order described by `pixelFormat`, then grouped in rows, from left to right,
  /// then top to bottom.
  ///
  /// The `rowBytes` parameter is the number of bytes consumed by each row of
  /// pixels in the data buffer. If unspecified, it defaults to `width` multiplied
  /// by the number of bytes per pixel in the provided `format`.
  // Not async because there's no expensive work to do here.
  _NativeImageDescriptor.raw(
    ImmutableBuffer buffer, {
    required int width,
    required int height,
    int? rowBytes,
    required PixelFormat pixelFormat,
  }) {
    _width = width;
    _height = height;
    // We only support 4 byte pixel formats in the PixelFormat enum.
    _bytesPerPixel = 4;
    _initRaw(this, buffer, width, height, rowBytes ?? -1, pixelFormat.index);
  }

  @Native<Handle Function(Handle, Pointer<Void>, Handle)>(symbol: 'ImageDescriptor::initEncoded')
  external String? _initEncoded(ImmutableBuffer buffer, _Callback<void> callback);

  @Native<Void Function(Handle, Handle, Int32, Int32, Int32, Int32)>(
    symbol: 'ImageDescriptor::initRaw',
  )
  external static void _initRaw(
    ImageDescriptor outDescriptor,
    ImmutableBuffer buffer,
    int width,
    int height,
    int rowBytes,
    int pixelFormat,
  );

  int? _width;

  @Native<Int32 Function(Pointer<Void>)>(symbol: 'ImageDescriptor::width', isLeaf: true)
  external int _getWidth();

  @override
  int get width => _width ??= _getWidth();

  int? _height;

  @Native<Int32 Function(Pointer<Void>)>(symbol: 'ImageDescriptor::height', isLeaf: true)
  external int _getHeight();

  @override
  int get height => _height ??= _getHeight();

  int? _bytesPerPixel;

  @Native<Int32 Function(Pointer<Void>)>(symbol: 'ImageDescriptor::bytesPerPixel', isLeaf: true)
  external int _getBytesPerPixel();

  @override
  int get bytesPerPixel => _bytesPerPixel ??= _getBytesPerPixel();

  @override
  @Native<Void Function(Pointer<Void>)>(symbol: 'ImageDescriptor::dispose')
  external void dispose();

  @override
  Future<Codec> instantiateCodec({
    int? targetWidth,
    int? targetHeight,
    TargetPixelFormat targetFormat = TargetPixelFormat.dontCare,
  }) async {
    if (targetWidth != null && targetWidth <= 0) {
      targetWidth = null;
    }
    if (targetHeight != null && targetHeight <= 0) {
      targetHeight = null;
    }

    if (targetWidth == null && targetHeight == null) {
      targetWidth = width;
      targetHeight = height;
    } else if (targetWidth == null && targetHeight != null) {
      targetWidth = (targetHeight * (width / height)).round();
    } else if (targetHeight == null && targetWidth != null) {
      targetHeight = targetWidth ~/ (width / height);
    }
    assert(targetWidth != null);
    assert(targetHeight != null);

    final Codec codec = _NativeCodec._();
    _instantiateCodec(codec, targetWidth!, targetHeight!, targetFormat.index);
    return codec;
  }

  @Native<Void Function(Pointer<Void>, Handle, Int32, Int32, Int32)>(
    symbol: 'ImageDescriptor::instantiateCodec',
  )
  external void _instantiateCodec(
    Codec outCodec,
    int targetWidth,
    int targetHeight,
    int targetFormat,
  );

  @override
  String toString() =>
      'ImageDescriptor(width: ${_width ?? '?'}, height: ${_height ?? '?'}, bytes per pixel: ${_bytesPerPixel ?? '?'})';
}

/// Generic callback signature, used by [_futurize].
typedef _Callback<T> = void Function(T result);

/// Generic callback signature, used by [_futurizeWithError].
typedef _CallbackWithError<T> = void Function(T result, String? error);

/// Signature for a method that receives a [_Callback].
///
/// Return value should be null on success, and a string error message on
/// failure.
typedef _Callbacker<T> = String? Function(_Callback<T?> callback);

/// Signature for a method that receives a [_CallbackWithError].
/// See also: [_Callbacker]
typedef _CallbackerWithError<T> = String? Function(_CallbackWithError<T?> callback);

// Converts a method that receives a value-returning callback to a method that
// returns a Future.
//
// Return a [String] to cause an [Exception] to be synchronously thrown with
// that string as a message.
//
// If the callback is called with null, the future completes with an error.
//
// Example usage:
//
// ```dart
// typedef IntCallback = void Function(int result);
//
// String? _doSomethingAndCallback(IntCallback callback) {
//   Timer(const Duration(seconds: 1), () { callback(1); });
// }
//
// Future<int> doSomething() {
//   return _futurize(_doSomethingAndCallback);
// }
// ```
//
// This function is private and so not directly tested. Instead, an exact copy of it
// has been inlined into the test at lib/ui/fixtures/ui_test.dart. if you change this
// function, then you must update the test.
//
// TODO(ianh): We should either automate the code duplication or just make it public.
Future<T> _futurize<T>(_Callbacker<T> callbacker) {
  final completer = Completer<T>.sync();
  // If the callback synchronously throws an error, then synchronously
  // rethrow that error instead of adding it to the completer. This
  // prevents the Zone from receiving an uncaught exception.
  var isSync = true;
  final String? error = callbacker((T? t) {
    if (t == null) {
      if (isSync) {
        throw Exception('operation failed');
      } else {
        completer.completeError(Exception('operation failed'));
      }
    } else {
      completer.complete(t);
    }
  });
  isSync = false;
  if (error != null) {
    throw Exception(error);
  }
  return completer.future;
}

/// A variant of `_futurize` that can communicate specific errors.
Future<T> _futurizeWithError<T>(_CallbackerWithError<T> callbacker) {
  final completer = Completer<T>.sync();
  // If the callback synchronously throws an error, then synchronously
  // rethrow that error instead of adding it to the completer. This
  // prevents the Zone from receiving an uncaught exception.
  var isSync = true;
  final String? error = callbacker((T? t, String? error) {
    if (t != null) {
      completer.complete(t);
    } else {
      if (isSync) {
        throw Exception(error ?? 'operation failed');
      } else {
        completer.completeError(Exception(error ?? 'operation failed'));
      }
    }
  });
  isSync = false;
  if (error != null) {
    throw Exception(error);
  }
  return completer.future;
}

/// An exception thrown by [Canvas.drawImage] and related methods when drawing
/// an [Image] created via [Picture.toImageSync] that is in an invalid state.
///
/// This exception may be thrown if the requested image dimensions exceeded the
/// maximum 2D texture size allowed by the GPU, or if no GPU surface or context
/// was available for rasterization at request time.
class PictureRasterizationException implements Exception {
  const PictureRasterizationException._(this.message, {this.stack});

  /// A string containing details about the failure.
  final String message;

  /// If available, the stack trace at the time [Picture.toImageSync] was called.
  final StackTrace? stack;

  @override
  String toString() {
    final buffer = StringBuffer('Failed to rasterize a picture: $message.');
    if (stack != null) {
      buffer.writeln();
      buffer.writeln('The callstack when the image was created was:');
      buffer.writeln(stack!.toString());
    }
    return buffer.toString();
  }
}