packages/flutter/lib/src/material/text_theme.dart

// Copyright 2014 The Flutter Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

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

import 'typography.dart';

/// Material design text theme.
///
/// Definitions for the various typographical styles found in Material Design
/// (e.g., button, caption). Rather than creating a [TextTheme] directly,
/// you can obtain an instance as [Typography.black] or [Typography.white].
///
/// To obtain the current text theme, call [Theme.of] with the current
/// [BuildContext] and read the [ThemeData.textTheme] property.
///
/// The names of the TextTheme properties match this table from the
/// [Material Design spec](https://m3.material.io/styles/typography/tokens).
///
/// ![](https://lh3.googleusercontent.com/Yvngs5mQSjXa_9T4X3JDucO62c5hdZHPDa7qeRH6DsJQvGr_q7EBrTkhkPiQd9OeR1v_Uk38Cjd9nUpP3nevDyHpKWuXSfQ1Gq78bOnBN7sr=s0)
///
/// The Material Design typography scheme was significantly changed in the
/// current (2021) version of the specification
/// ([https://m3.material.io/styles/typography/tokens](https://m3.material.io/styles/typography/tokens)).
///
/// The names of the 2018 TextTheme properties match this table from the
/// [Material Design spec](https://material.io/design/typography/the-type-system.html#type-scale)
/// with two exceptions: the styles called H1-H6 in the spec are
/// headline1-headline6 in the API, and body1,body2 are called
/// bodyText1 and bodyText2.
///
/// The 2018 spec has thirteen text styles:
/// ```
/// NAME         SIZE  WEIGHT  SPACING
/// headline1    96.0  light   -1.5
/// headline2    60.0  light   -0.5
/// headline3    48.0  regular  0.0
/// headline4    34.0  regular  0.25
/// headline5    24.0  regular  0.0
/// headline6    20.0  medium   0.15
/// subtitle1    16.0  regular  0.15
/// subtitle2    14.0  medium   0.1
/// body1        16.0  regular  0.5   (bodyText1)
/// body2        14.0  regular  0.25  (bodyText2)
/// button       14.0  medium   1.25
/// caption      12.0  regular  0.4
/// overline     10.0  regular  1.5
/// ```
///
/// ...where "light" is `FontWeight.w300`, "regular" is `FontWeight.w400` and
/// "medium" is `FontWeight.w500`.
///
/// By default, text styles are initialized to match the 2018 Material Design
/// specification as listed above. To provide backwards compatibility, the 2014
/// specification is also available.
///
/// To explicitly configure a [Theme] for the 2018 sizes, weights, and letter
/// spacings, you can initialize its [ThemeData.typography] value using
/// [Typography.material2018]. The [Typography] constructor defaults to this
/// configuration. To configure a [Theme] for the 2014 sizes, weights, and letter
/// spacings, initialize its [ThemeData.typography] value using
/// [Typography.material2014].
///
/// See also:
///
///  * [Typography], the class that generates [TextTheme]s appropriate for a platform.
///  * [Theme], for other aspects of a Material Design application that can be
///    globally adjusted, such as the color scheme.
///  * <https://material.io/design/typography/>
@immutable
class TextTheme with Diagnosticable {
  /// Creates a text theme that uses the given values.
  ///
  /// Rather than creating a new text theme, consider using [Typography.black]
  /// or [Typography.white], which implement the typography styles in the
  /// Material Design specification:
  ///
  /// <https://material.io/design/typography/#type-scale>
  ///
  /// If you do decide to create your own text theme, consider using one of
  /// those predefined themes as a starting point for [copyWith] or [apply].
  ///
  /// Please note that you can not mix and match the 2018 styles with the 2021
  /// styles. Only one or the other is allowed in this constructor. The 2018
  /// styles will be deprecated and removed eventually.
  const TextTheme({
    TextStyle? displayLarge,
    TextStyle? displayMedium,
    TextStyle? displaySmall,
    this.headlineLarge,
    TextStyle? headlineMedium,
    TextStyle? headlineSmall,
    TextStyle? titleLarge,
    TextStyle? titleMedium,
    TextStyle? titleSmall,
    TextStyle? bodyLarge,
    TextStyle? bodyMedium,
    TextStyle? bodySmall,
    TextStyle? labelLarge,
    this.labelMedium,
    TextStyle? labelSmall,
    TextStyle? headline1,
    TextStyle? headline2,
    TextStyle? headline3,
    TextStyle? headline4,
    TextStyle? headline5,
    TextStyle? headline6,
    TextStyle? subtitle1,
    TextStyle? subtitle2,
    TextStyle? bodyText1,
    TextStyle? bodyText2,
    TextStyle? caption,
    TextStyle? button,
    TextStyle? overline,
  }) : assert(
         (displayLarge == null && displayMedium == null && displaySmall == null && headlineMedium == null &&
             headlineSmall == null && titleLarge == null && titleMedium == null && titleSmall == null &&
             bodyLarge == null && bodyMedium == null && bodySmall == null && labelLarge == null && labelSmall == null) ||
         (headline1 == null && headline2 == null && headline3 == null && headline4 == null &&
             headline5 == null && headline6 == null && subtitle1 == null && subtitle2 == null &&
             bodyText1 == null && bodyText2 == null && caption == null && button == null && overline == null),
         'Cannot mix 2018 and 2021 terms in call to TextTheme() constructor.'
       ),
       displayLarge = displayLarge ?? headline1,
       displayMedium = displayMedium ?? headline2,
       displaySmall = displaySmall ?? headline3,
       headlineMedium = headlineMedium ?? headline4,
       headlineSmall = headlineSmall ?? headline5,
       titleLarge = titleLarge ?? headline6,
       titleMedium = titleMedium ?? subtitle1,
       titleSmall = titleSmall ?? subtitle2,
       bodyLarge = bodyLarge ?? bodyText1,
       bodyMedium = bodyMedium ?? bodyText2,
       bodySmall = bodySmall ?? caption,
       labelLarge = labelLarge ?? button,
       labelSmall = labelSmall ?? overline;

  /// Largest of the display styles.
  ///
  /// As the largest text on the screen, display styles are reserved for short,
  /// important text or numerals. They work best on large screens.
  final TextStyle? displayLarge;

  /// Middle size of the display styles.
  ///
  /// As the largest text on the screen, display styles are reserved for short,
  /// important text or numerals. They work best on large screens.
  final TextStyle? displayMedium;

  /// Smallest of the display styles.
  ///
  /// As the largest text on the screen, display styles are reserved for short,
  /// important text or numerals. They work best on large screens.
  final TextStyle? displaySmall;

  /// Largest of the headline styles.
  ///
  /// Headline styles are smaller than display styles. They're best-suited for
  /// short, high-emphasis text on smaller screens.
  final TextStyle? headlineLarge;

  /// Middle size of the headline styles.
  ///
  /// Headline styles are smaller than display styles. They're best-suited for
  /// short, high-emphasis text on smaller screens.
  final TextStyle? headlineMedium;

  /// Smallest of the headline styles.
  ///
  /// Headline styles are smaller than display styles. They're best-suited for
  /// short, high-emphasis text on smaller screens.
  final TextStyle? headlineSmall;

  /// Largest of the title styles.
  ///
  /// Titles are smaller than headline styles and should be used for shorter,
  /// medium-emphasis text.
  final TextStyle? titleLarge;

  /// Middle size of the title styles.
  ///
  /// Titles are smaller than headline styles and should be used for shorter,
  /// medium-emphasis text.
  final TextStyle? titleMedium;

  /// Smallest of the title styles.
  ///
  /// Titles are smaller than headline styles and should be used for shorter,
  /// medium-emphasis text.
  final TextStyle? titleSmall;

  /// Largest of the body styles.
  ///
  /// Body styles are used for longer passages of text.
  final TextStyle? bodyLarge;

  /// Middle size of the body styles.
  ///
  /// Body styles are used for longer passages of text.
  ///
  /// The default text style for [Material].
  final TextStyle? bodyMedium;

  /// Smallest of the body styles.
  ///
  /// Body styles are used for longer passages of text.
  final TextStyle? bodySmall;

  /// Largest of the label styles.
  ///
  /// Label styles are smaller, utilitarian styles, used for areas of the UI
  /// such as text inside of components or very small supporting text in the
  /// content body, like captions.
  ///
  /// Used for text on [ElevatedButton], [TextButton] and [OutlinedButton].
  final TextStyle? labelLarge;

  /// Middle size of the label styles.
  ///
  /// Label styles are smaller, utilitarian styles, used for areas of the UI
  /// such as text inside of components or very small supporting text in the
  /// content body, like captions.
  final TextStyle? labelMedium;

  /// Smallest of the label styles.
  ///
  /// Label styles are smaller, utilitarian styles, used for areas of the UI
  /// such as text inside of components or very small supporting text in the
  /// content body, like captions.
  final TextStyle? labelSmall;

  /// Extremely large text.
  TextStyle? get headline1 => displayLarge;

  /// Very, very large text.
  ///
  /// Used for the date in the dialog shown by [showDatePicker].
  TextStyle? get headline2 => displayMedium;

  /// Very large text.
  TextStyle? get headline3 => displaySmall;

  /// Large text.
  TextStyle? get headline4 => headlineMedium;

  /// Used for large text in dialogs (e.g., the month and year in the dialog
  /// shown by [showDatePicker]).
  TextStyle? get headline5 => headlineSmall;

  /// Used for the primary text in app bars and dialogs (e.g., [AppBar.title]
  /// and [AlertDialog.title]).
  TextStyle? get headline6 => titleLarge;

  /// Used for the primary text in lists (e.g., [ListTile.title]).
  TextStyle? get subtitle1 => titleMedium;

  /// For medium emphasis text that's a little smaller than [subtitle1].
  TextStyle? get subtitle2 => titleSmall;

  /// Used for emphasizing text that would otherwise be [bodyText2].
  TextStyle? get bodyText1 => bodyLarge;

  /// The default text style for [Material].
  TextStyle? get bodyText2 => bodyMedium;

  /// Used for auxiliary text associated with images.
  TextStyle? get caption => bodySmall;

  /// Used for text on [ElevatedButton], [TextButton] and [OutlinedButton].
  TextStyle? get button => labelLarge;

  /// The smallest style.
  ///
  /// Typically used for captions or to introduce a (larger) headline.
  TextStyle? get overline => labelSmall;

  /// Creates a copy of this text theme but with the given fields replaced with
  /// the new values.
  ///
  /// Consider using [Typography.black] or [Typography.white], which implement
  /// the typography styles in the Material Design specification, as a starting
  /// point.
  ///
  /// {@tool snippet}
  ///
  /// ```dart
  /// /// A Widget that sets the ambient theme's title text color for its
  /// /// descendants, while leaving other ambient theme attributes alone.
  /// class TitleColorThemeCopy extends StatelessWidget {
  ///   const TitleColorThemeCopy({Key? key, required this.child, required this.titleColor}) : super(key: key);
  ///
  ///   final Color titleColor;
  ///   final Widget child;
  ///
  ///   @override
  ///   Widget build(BuildContext context) {
  ///     final ThemeData theme = Theme.of(context);
  ///     return Theme(
  ///       data: theme.copyWith(
  ///         textTheme: theme.textTheme.copyWith(
  ///           titleLarge: theme.textTheme.titleLarge!.copyWith(
  ///             color: titleColor,
  ///           ),
  ///         ),
  ///       ),
  ///       child: child,
  ///     );
  ///   }
  /// }
  /// ```
  /// {@end-tool}
  ///
  /// See also:
  ///
  ///  * [merge] is used instead of [copyWith] when you want to merge all
  ///    of the fields of a TextTheme instead of individual fields.
  TextTheme copyWith({
    TextStyle? displayLarge,
    TextStyle? displayMedium,
    TextStyle? displaySmall,
    TextStyle? headlineLarge,
    TextStyle? headlineMedium,
    TextStyle? headlineSmall,
    TextStyle? titleLarge,
    TextStyle? titleMedium,
    TextStyle? titleSmall,
    TextStyle? bodyLarge,
    TextStyle? bodyMedium,
    TextStyle? bodySmall,
    TextStyle? labelLarge,
    TextStyle? labelMedium,
    TextStyle? labelSmall,
    TextStyle? headline1,
    TextStyle? headline2,
    TextStyle? headline3,
    TextStyle? headline4,
    TextStyle? headline5,
    TextStyle? headline6,
    TextStyle? subtitle1,
    TextStyle? subtitle2,
    TextStyle? bodyText1,
    TextStyle? bodyText2,
    TextStyle? caption,
    TextStyle? button,
    TextStyle? overline,
  }) {
    assert(
      (displayLarge == null && displayMedium == null && displaySmall == null && headlineMedium == null &&
          headlineSmall == null && titleLarge == null && titleMedium == null && titleSmall == null &&
          bodyLarge == null && bodyMedium == null && bodySmall == null && labelLarge == null && labelSmall == null) ||
      (headline1 == null && headline2 == null && headline3 == null && headline4 == null &&
          headline5 == null && headline6 == null && subtitle1 == null && subtitle2 == null &&
          bodyText1 == null && bodyText2 == null && caption == null && button == null && overline == null),
      'Cannot mix 2018 and 2021 terms in call to TextTheme() constructor.'
    );
    return TextTheme(
      displayLarge: displayLarge ?? headline1 ?? this.displayLarge,
      displayMedium: displayMedium ?? headline2 ?? this.displayMedium,
      displaySmall: displaySmall ?? headline3 ?? this.displaySmall,
      headlineLarge: headlineLarge ?? this.headlineLarge,
      headlineMedium: headlineMedium ?? headline4 ?? this.headlineMedium,
      headlineSmall: headlineSmall ?? headline5 ?? this.headlineSmall,
      titleLarge: titleLarge ?? headline6 ?? this.titleLarge,
      titleMedium: titleMedium ?? subtitle1 ?? this.titleMedium,
      titleSmall: titleSmall ?? subtitle2 ?? this.titleSmall,
      bodyLarge: bodyLarge ?? bodyText1 ?? this.bodyLarge,
      bodyMedium: bodyMedium ?? bodyText2 ?? this.bodyMedium,
      bodySmall: bodySmall ?? caption ?? this.bodySmall,
      labelLarge: labelLarge ?? button ?? this.labelLarge,
      labelMedium: labelMedium ?? this.labelMedium,
      labelSmall: labelSmall ?? overline ?? this.labelSmall,
    );
  }

  /// Creates a new [TextTheme] where each text style from this object has been
  /// merged with the matching text style from the `other` object.
  ///
  /// The merging is done by calling [TextStyle.merge] on each respective pair
  /// of text styles from this and the [other] text themes and is subject to
  /// the value of [TextStyle.inherit] flag. For more details, see the
  /// documentation on [TextStyle.merge] and [TextStyle.inherit].
  ///
  /// If this theme, or the `other` theme has members that are null, then the
  /// non-null one (if any) is used. If the `other` theme is itself null, then
  /// this [TextTheme] is returned unchanged. If values in both are set, then
  /// the values are merged using [TextStyle.merge].
  ///
  /// This is particularly useful if one [TextTheme] defines one set of
  /// properties and another defines a different set, e.g. having colors
  /// defined in one text theme and font sizes in another, or when one
  /// [TextTheme] has only some fields defined, and you want to define the rest
  /// by merging it with a default theme.
  ///
  /// {@tool snippet}
  ///
  /// ```dart
  /// /// A Widget that sets the ambient theme's title text color for its
  /// /// descendants, while leaving other ambient theme attributes alone.
  /// class TitleColorTheme extends StatelessWidget {
  ///   const TitleColorTheme({Key? key, required this.child, required this.titleColor}) : super(key: key);
  ///
  ///   final Color titleColor;
  ///   final Widget child;
  ///
  ///   @override
  ///   Widget build(BuildContext context) {
  ///     ThemeData theme = Theme.of(context);
  ///     // This partialTheme is incomplete: it only has the title style
  ///     // defined. Just replacing theme.textTheme with partialTheme would
  ///     // set the title, but everything else would be null. This isn't very
  ///     // useful, so merge it with the existing theme to keep all of the
  ///     // preexisting definitions for the other styles.
  ///     final TextTheme partialTheme = TextTheme(titleLarge: TextStyle(color: titleColor));
  ///     theme = theme.copyWith(textTheme: theme.textTheme.merge(partialTheme));
  ///     return Theme(data: theme, child: child);
  ///   }
  /// }
  /// ```
  /// {@end-tool}
  ///
  /// See also:
  ///
  ///  * [copyWith] is used instead of [merge] when you wish to override
  ///    individual fields in the [TextTheme] instead of merging all of the
  ///    fields of two [TextTheme]s.
  TextTheme merge(TextTheme? other) {
    if (other == null)
      return this;
    return copyWith(
      displayLarge: displayLarge?.merge(other.displayLarge) ?? other.displayLarge,
      displayMedium: displayMedium?.merge(other.displayMedium) ?? other.displayMedium,
      displaySmall: displaySmall?.merge(other.displaySmall) ?? other.displaySmall,
      headlineLarge: headlineLarge?.merge(other.headlineLarge) ?? other.headlineLarge,
      headlineMedium: headlineMedium?.merge(other.headlineMedium) ?? other.headlineMedium,
      headlineSmall: headlineSmall?.merge(other.headlineSmall) ?? other.headlineSmall,
      titleLarge: titleLarge?.merge(other.titleLarge) ?? other.titleLarge,
      titleMedium: titleMedium?.merge(other.titleMedium) ?? other.titleMedium,
      titleSmall: titleSmall?.merge(other.titleSmall) ?? other.titleSmall,
      bodyLarge: bodyLarge?.merge(other.bodyLarge) ?? other.bodyLarge,
      bodyMedium: bodyMedium?.merge(other.bodyMedium) ?? other.bodyMedium,
      bodySmall: bodySmall?.merge(other.bodySmall) ?? other.bodySmall,
      labelLarge: labelLarge?.merge(other.labelLarge) ?? other.labelLarge,
      labelMedium: labelMedium?.merge(other.labelMedium) ?? other.labelMedium,
      labelSmall: labelSmall?.merge(other.labelSmall) ?? other.labelSmall,
    );
  }

  /// Creates a copy of this text theme but with the given field replaced in
  /// each of the individual text styles.
  ///
  /// The `displayColor` is applied to [displayLarge], [displayMedium],
  /// [displaySmall], [headlineLarge], [headlineMedium], and [bodySmall]. The
  /// `bodyColor` is applied to the remaining text styles.
  ///
  /// Consider using [Typography.black] or [Typography.white], which implement
  /// the typography styles in the Material Design specification, as a starting
  /// point.
  TextTheme apply({
    String? fontFamily,
    double fontSizeFactor = 1.0,
    double fontSizeDelta = 0.0,
    Color? displayColor,
    Color? bodyColor,
    TextDecoration? decoration,
    Color? decorationColor,
    TextDecorationStyle? decorationStyle,
  }) {
    return TextTheme(
      displayLarge: displayLarge?.apply(
        color: displayColor,
        decoration: decoration,
        decorationColor: decorationColor,
        decorationStyle: decorationStyle,
        fontFamily: fontFamily,
        fontSizeFactor: fontSizeFactor,
        fontSizeDelta: fontSizeDelta,
      ),
      displayMedium: displayMedium?.apply(
        color: displayColor,
        decoration: decoration,
        decorationColor: decorationColor,
        decorationStyle: decorationStyle,
        fontFamily: fontFamily,
        fontSizeFactor: fontSizeFactor,
        fontSizeDelta: fontSizeDelta,
      ),
      displaySmall: displaySmall?.apply(
        color: displayColor,
        decoration: decoration,
        decorationColor: decorationColor,
        decorationStyle: decorationStyle,
        fontFamily: fontFamily,
        fontSizeFactor: fontSizeFactor,
        fontSizeDelta: fontSizeDelta,
      ),
      headlineLarge: headlineLarge?.apply(
        color: displayColor,
        decoration: decoration,
        decorationColor: decorationColor,
        decorationStyle: decorationStyle,
        fontFamily: fontFamily,
        fontSizeFactor: fontSizeFactor,
        fontSizeDelta: fontSizeDelta,
      ),
      headlineMedium: headlineMedium?.apply(
        color: displayColor,
        decoration: decoration,
        decorationColor: decorationColor,
        decorationStyle: decorationStyle,
        fontFamily: fontFamily,
        fontSizeFactor: fontSizeFactor,
        fontSizeDelta: fontSizeDelta,
      ),
      headlineSmall: headlineSmall?.apply(
        color: bodyColor,
        decoration: decoration,
        decorationColor: decorationColor,
        decorationStyle: decorationStyle,
        fontFamily: fontFamily,
        fontSizeFactor: fontSizeFactor,
        fontSizeDelta: fontSizeDelta,
      ),
      titleLarge: titleLarge?.apply(
        color: bodyColor,
        decoration: decoration,
        decorationColor: decorationColor,
        decorationStyle: decorationStyle,
        fontFamily: fontFamily,
        fontSizeFactor: fontSizeFactor,
        fontSizeDelta: fontSizeDelta,
      ),
      titleMedium: titleMedium?.apply(
        color: bodyColor,
        decoration: decoration,
        decorationColor: decorationColor,
        decorationStyle: decorationStyle,
        fontFamily: fontFamily,
        fontSizeFactor: fontSizeFactor,
        fontSizeDelta: fontSizeDelta,
      ),
      titleSmall: titleSmall?.apply(
        color: bodyColor,
        decoration: decoration,
        decorationColor: decorationColor,
        decorationStyle: decorationStyle,
        fontFamily: fontFamily,
        fontSizeFactor: fontSizeFactor,
        fontSizeDelta: fontSizeDelta,
      ),
      bodyLarge: bodyLarge?.apply(
        color: bodyColor,
        decoration: decoration,
        decorationColor: decorationColor,
        decorationStyle: decorationStyle,
        fontFamily: fontFamily,
        fontSizeFactor: fontSizeFactor,
        fontSizeDelta: fontSizeDelta,
      ),
      bodyMedium: bodyMedium?.apply(
        color: bodyColor,
        decoration: decoration,
        decorationColor: decorationColor,
        decorationStyle: decorationStyle,
        fontFamily: fontFamily,
        fontSizeFactor: fontSizeFactor,
        fontSizeDelta: fontSizeDelta,
      ),
      bodySmall: bodySmall?.apply(
        color: displayColor,
        decoration: decoration,
        decorationColor: decorationColor,
        decorationStyle: decorationStyle,
        fontFamily: fontFamily,
        fontSizeFactor: fontSizeFactor,
        fontSizeDelta: fontSizeDelta,
      ),
      labelLarge: labelLarge?.apply(
        color: bodyColor,
        decoration: decoration,
        decorationColor: decorationColor,
        decorationStyle: decorationStyle,
        fontFamily: fontFamily,
        fontSizeFactor: fontSizeFactor,
        fontSizeDelta: fontSizeDelta,
      ),
      labelMedium: labelMedium?.apply(
        color: bodyColor,
        decoration: decoration,
        decorationColor: decorationColor,
        decorationStyle: decorationStyle,
        fontFamily: fontFamily,
        fontSizeFactor: fontSizeFactor,
        fontSizeDelta: fontSizeDelta,
      ),
      labelSmall: labelSmall?.apply(
        color: bodyColor,
        decoration: decoration,
        decorationColor: decorationColor,
        decorationStyle: decorationStyle,
        fontFamily: fontFamily,
        fontSizeFactor: fontSizeFactor,
        fontSizeDelta: fontSizeDelta,
      ),
    );
  }

  /// Linearly interpolate between two text themes.
  ///
  /// {@macro dart.ui.shadow.lerp}
  static TextTheme lerp(TextTheme? a, TextTheme? b, double t) {
    assert(t != null);
    return TextTheme(
      displayLarge: TextStyle.lerp(a?.displayLarge, b?.displayLarge, t),
      displayMedium: TextStyle.lerp(a?.displayMedium, b?.displayMedium, t),
      displaySmall: TextStyle.lerp(a?.displaySmall, b?.displaySmall, t),
      headlineLarge: TextStyle.lerp(a?.headlineLarge, b?.headlineLarge, t),
      headlineMedium: TextStyle.lerp(a?.headlineMedium, b?.headlineMedium, t),
      headlineSmall: TextStyle.lerp(a?.headlineSmall, b?.headlineSmall, t),
      titleLarge: TextStyle.lerp(a?.titleLarge, b?.titleLarge, t),
      titleMedium: TextStyle.lerp(a?.titleMedium, b?.titleMedium, t),
      titleSmall: TextStyle.lerp(a?.titleSmall, b?.titleSmall, t),
      bodyLarge: TextStyle.lerp(a?.bodyLarge, b?.bodyLarge, t),
      bodyMedium: TextStyle.lerp(a?.bodyMedium, b?.bodyMedium, t),
      bodySmall: TextStyle.lerp(a?.bodySmall, b?.bodySmall, t),
      labelLarge: TextStyle.lerp(a?.labelLarge, b?.labelLarge, t),
      labelMedium: TextStyle.lerp(a?.labelMedium, b?.labelMedium, t),
      labelSmall: TextStyle.lerp(a?.labelSmall, b?.labelSmall, t),
    );
  }

  @override
  bool operator ==(Object other) {
    if (identical(this, other))
      return true;
    if (other.runtimeType != runtimeType)
      return false;
    return other is TextTheme
      && displayLarge == other.displayLarge
      && displayMedium == other.displayMedium
      && displaySmall == other.displaySmall
      && headlineLarge == other.headlineLarge
      && headlineMedium == other.headlineMedium
      && headlineSmall == other.headlineSmall
      && titleLarge == other.titleLarge
      && titleMedium == other.titleMedium
      && titleSmall == other.titleSmall
      && bodyLarge == other.bodyLarge
      && bodyMedium == other.bodyMedium
      && bodySmall == other.bodySmall
      && labelLarge == other.labelLarge
      && labelMedium == other.labelMedium
      && labelSmall == other.labelSmall;
  }

  @override
  int get hashCode => Object.hash(
    displayLarge,
    displayMedium,
    displaySmall,
    headlineLarge,
    headlineMedium,
    headlineSmall,
    titleLarge,
    titleMedium,
    titleSmall,
    bodyLarge,
    bodyMedium,
    bodySmall,
    labelLarge,
    labelMedium,
    labelSmall,
  );

  @override
  void debugFillProperties(DiagnosticPropertiesBuilder properties) {
    super.debugFillProperties(properties);
    final TextTheme defaultTheme = Typography.material2018(platform: defaultTargetPlatform).black;
    properties.add(DiagnosticsProperty<TextStyle>('displayLarge', displayLarge, defaultValue: defaultTheme.displayLarge));
    properties.add(DiagnosticsProperty<TextStyle>('displayMedium', displayMedium, defaultValue: defaultTheme.displayMedium));
    properties.add(DiagnosticsProperty<TextStyle>('displaySmall', displaySmall, defaultValue: defaultTheme.displaySmall));
    properties.add(DiagnosticsProperty<TextStyle>('headlineLarge', headlineLarge, defaultValue: defaultTheme.headlineLarge));
    properties.add(DiagnosticsProperty<TextStyle>('headlineMedium', headlineMedium, defaultValue: defaultTheme.headlineMedium));
    properties.add(DiagnosticsProperty<TextStyle>('headlineSmall', headlineSmall, defaultValue: defaultTheme.headlineSmall));
    properties.add(DiagnosticsProperty<TextStyle>('titleLarge', titleLarge, defaultValue: defaultTheme.titleLarge));
    properties.add(DiagnosticsProperty<TextStyle>('titleMedium', titleMedium, defaultValue: defaultTheme.titleMedium));
    properties.add(DiagnosticsProperty<TextStyle>('titleSmall', titleSmall, defaultValue: defaultTheme.titleSmall));
    properties.add(DiagnosticsProperty<TextStyle>('bodyLarge', bodyLarge, defaultValue: defaultTheme.bodyLarge));
    properties.add(DiagnosticsProperty<TextStyle>('bodyMedium', bodyMedium, defaultValue: defaultTheme.bodyMedium));
    properties.add(DiagnosticsProperty<TextStyle>('bodySmall', bodySmall, defaultValue: defaultTheme.bodySmall));
    properties.add(DiagnosticsProperty<TextStyle>('labelLarge', labelLarge, defaultValue: defaultTheme.labelLarge));
    properties.add(DiagnosticsProperty<TextStyle>('labelMedium', labelMedium, defaultValue: defaultTheme.labelMedium));
    properties.add(DiagnosticsProperty<TextStyle>('labelSmall', labelSmall, defaultValue: defaultTheme.labelSmall));
  }
}