packages/flutter/lib/src/material/text_theme.dart - mirrors/flutter - Git at Google

 // Copyright 2018 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.

 import '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 Material Design typography scheme was significantly changed in the
 /// current (2018) version of the specification
 /// (https://material.io/design/typography).
 ///
 /// 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  normal   0.0
 /// headline4    34.0  normal   0.25
 /// headline5    24.0  normal   0.0
 /// headline6    20.0  medium   0.15
 /// subtitle1    16.0  normal   0.15
 /// subtitle2    14.0  medium   0.1
 /// body1        16.0  normal   0.5
 /// body2        14.0  normal   0.25
 /// button       14.0  medium   0.75
 /// caption      12.0  normal   0.4
 /// overline     10.0  normal   1.5
 ///
 /// ```
 /// Where "light" is `FontWeight.w300`, "normal" is `FontWeight.w400` and
 /// "medium" is `FontWeight.w500`.
 ///
 /// The [TextTheme] API is based on the original material (2014)
 /// design spec, which used different text style names. For backwards
 /// compatibility's sake, this API continues to use the original
 /// names. The table below should help with understanding the API in
 /// terms of the 2018 material spec.
 ///
 /// Each of the [TextTheme] text styles corresponds to one of the
 /// styles from 2018 spec. By default, the font sizes, font weights
 /// and letter spacings have not changed from their original,
 /// 2014, values.
 /// ```
 /// NAME       SIZE   WEIGHT   SPACING  2018 NAME
 /// display4   112.0  thin     0.0      headline1
 /// display3   56.0   normal   0.0      headline2
 /// display2   45.0   normal   0.0      headline3
 /// display1   34.0   normal   0.0      headline4
 /// headline   24.0   normal   0.0      headline5
 /// title      20.0   medium   0.0      headline6
 /// subhead    16.0   normal   0.0      subtitle1
 /// body2      14.0   medium   0.0      body1
 /// body1      14.0   normal   0.0      body2
 /// caption    12.0   normal   0.0      caption
 /// button     14.0   medium   0.0      button
 /// subtitle   14.0   medium   0.0      subtitle2
 /// overline   10.0   normal   0.0      overline
 /// ```
 ///
 /// Where "thin" is `FontWeight.w100`, "normal" is `FontWeight.w400` and
 /// "medium" is `FontWeight.w500`. Letter spacing for all of the original
 /// text styles was 0.0.
 ///
 /// To configure a [Theme] for the new sizes, weights, and letter spacings,
 /// initialize its [ThemeData.typography] value with a [Typography] that
 /// object that specifies the 2018 versions of the geometry themes:
 /// [Typography.englishLike2018], [Typography.dense2018],
 /// and [Typography.tall2018].
 ///
 /// The following image [from the material design
 /// specification](https://material.io/go/design-typography#typography-styles)
 /// shows the recommended styles for each of the properties of a [TextTheme].
 /// This image uses the `Roboto` font, which is the font used on Android. On
 /// iOS, the [San Francisco
 /// font](https://developer.apple.com/ios/human-interface-guidelines/visual-design/typography/)
 /// is automatically used instead.
 ///
 /// ![To see the image, visit the typography site referenced below.](https://storage.googleapis.com/material-design/publish/material_v_11/assets/0Bzhp5Z4wHba3alhXZ2pPWGk3Zjg/style_typography_styles_scale.png)
 ///
 /// 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 extends 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].
   const TextTheme({
     this.display4,
     this.display3,
     this.display2,
     this.display1,
     this.headline,
     this.title,
     this.subhead,
     this.body2,
     this.body1,
     this.caption,
     this.button,
     this.subtitle,
     this.overline,
   });

   /// Extremely large text.
   ///
   /// The font size is 112 pixels.
   final TextStyle display4;

   /// Very, very large text.
   ///
   /// Used for the date in the dialog shown by [showDatePicker].
   final TextStyle display3;

   /// Very large text.
   final TextStyle display2;

   /// Large text.
   final TextStyle display1;

   /// Used for large text in dialogs (e.g., the month and year in the dialog
   /// shown by [showDatePicker]).
   final TextStyle headline;

   /// Used for the primary text in app bars and dialogs (e.g., [AppBar.title]
   /// and [AlertDialog.title]).
   final TextStyle title;

   /// Used for the primary text in lists (e.g., [ListTile.title]).
   final TextStyle subhead;

   /// Used for emphasizing text that would otherwise be [body1].
   final TextStyle body2;

   /// Used for the default text style for [Material].
   final TextStyle body1;

   /// Used for auxiliary text associated with images.
   final TextStyle caption;

   /// Used for text on [RaisedButton] and [FlatButton].
   final TextStyle button;

   /// For medium emphasis text that's a little smaller than [subhead].
   final TextStyle subtitle;

   /// The smallest style,
   ///
   /// Typically used for captions or to introduce a (larger) headline.
   final TextStyle overline;

   /// 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 sample}
   ///
   /// ```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 {
   ///   TitleColorThemeCopy({Key key, this.child, 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(
   ///           title: theme.textTheme.title.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 display4,
     TextStyle display3,
     TextStyle display2,
     TextStyle display1,
     TextStyle headline,
     TextStyle title,
     TextStyle subhead,
     TextStyle body2,
     TextStyle body1,
     TextStyle caption,
     TextStyle button,
     TextStyle subtitle,
     TextStyle overline,
   }) {
     return TextTheme(
       display4: display4 ?? this.display4,
       display3: display3 ?? this.display3,
       display2: display2 ?? this.display2,
       display1: display1 ?? this.display1,
       headline: headline ?? this.headline,
       title: title ?? this.title,
       subhead: subhead ?? this.subhead,
       body2: body2 ?? this.body2,
       body1: body1 ?? this.body1,
       caption: caption ?? this.caption,
       button: button ?? this.button,
       subtitle: subtitle ?? this.subtitle,
       overline: overline ?? this.overline,
     );
   }

   /// 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 sample}
   ///
   /// ```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 {
   ///   TitleColorTheme({Key key, this.child, 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.
   ///     TextTheme partialTheme = TextTheme(title: 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(
       display4: display4?.merge(other.display4) ?? other.display4,
       display3: display3?.merge(other.display3) ?? other.display3,
       display2: display2?.merge(other.display2) ?? other.display2,
       display1: display1?.merge(other.display1) ?? other.display1,
       headline: headline?.merge(other.headline) ?? other.headline,
       title: title?.merge(other.title) ?? other.title,
       subhead: subhead?.merge(other.subhead) ?? other.subhead,
       body2: body2?.merge(other.body2) ?? other.body2,
       body1: body1?.merge(other.body1) ?? other.body1,
       caption: caption?.merge(other.caption) ?? other.caption,
       button: button?.merge(other.button) ?? other.button,
       subtitle: subtitle?.merge(other.subtitle) ?? other.subtitle,
       overline: overline?.merge(other.overline) ?? other.overline,
     );
   }

   /// 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 [display4], [display3], [display2],
   /// [display1], and [caption]. 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(
       display4: display4?.apply(
         color: displayColor,
         decoration: decoration,
         decorationColor: decorationColor,
         decorationStyle: decorationStyle,
         fontFamily: fontFamily,
         fontSizeFactor: fontSizeFactor,
         fontSizeDelta: fontSizeDelta,
       ),
       display3: display3?.apply(
         color: displayColor,
         decoration: decoration,
         decorationColor: decorationColor,
         decorationStyle: decorationStyle,
         fontFamily: fontFamily,
         fontSizeFactor: fontSizeFactor,
         fontSizeDelta: fontSizeDelta,
       ),
       display2: display2?.apply(
         color: displayColor,
         decoration: decoration,
         decorationColor: decorationColor,
         decorationStyle: decorationStyle,
         fontFamily: fontFamily,
         fontSizeFactor: fontSizeFactor,
         fontSizeDelta: fontSizeDelta,
       ),
       display1: display1?.apply(
         color: displayColor,
         decoration: decoration,
         decorationColor: decorationColor,
         decorationStyle: decorationStyle,
         fontFamily: fontFamily,
         fontSizeFactor: fontSizeFactor,
         fontSizeDelta: fontSizeDelta,
       ),
       headline: headline?.apply(
         color: bodyColor,
         decoration: decoration,
         decorationColor: decorationColor,
         decorationStyle: decorationStyle,
         fontFamily: fontFamily,
         fontSizeFactor: fontSizeFactor,
         fontSizeDelta: fontSizeDelta,
       ),
       title: title?.apply(
         color: bodyColor,
         decoration: decoration,
         decorationColor: decorationColor,
         decorationStyle: decorationStyle,
         fontFamily: fontFamily,
         fontSizeFactor: fontSizeFactor,
         fontSizeDelta: fontSizeDelta,
       ),
       subhead: subhead?.apply(
         color: bodyColor,
         decoration: decoration,
         decorationColor: decorationColor,
         decorationStyle: decorationStyle,
         fontFamily: fontFamily,
         fontSizeFactor: fontSizeFactor,
         fontSizeDelta: fontSizeDelta,
       ),
       body2: body2?.apply(
         color: bodyColor,
         decoration: decoration,
         decorationColor: decorationColor,
         decorationStyle: decorationStyle,
         fontFamily: fontFamily,
         fontSizeFactor: fontSizeFactor,
         fontSizeDelta: fontSizeDelta,
       ),
       body1: body1?.apply(
         color: bodyColor,
         decoration: decoration,
         decorationColor: decorationColor,
         decorationStyle: decorationStyle,
         fontFamily: fontFamily,
         fontSizeFactor: fontSizeFactor,
         fontSizeDelta: fontSizeDelta,
       ),
       caption: caption?.apply(
         color: displayColor,
         decoration: decoration,
         decorationColor: decorationColor,
         decorationStyle: decorationStyle,
         fontFamily: fontFamily,
         fontSizeFactor: fontSizeFactor,
         fontSizeDelta: fontSizeDelta,
       ),
       button: button?.apply(
         color: bodyColor,
         decoration: decoration,
         decorationColor: decorationColor,
         decorationStyle: decorationStyle,
         fontFamily: fontFamily,
         fontSizeFactor: fontSizeFactor,
         fontSizeDelta: fontSizeDelta,
       ),
       subtitle: subtitle?.apply(
         color: bodyColor,
         decoration: decoration,
         decorationColor: decorationColor,
         decorationStyle: decorationStyle,
         fontFamily: fontFamily,
         fontSizeFactor: fontSizeFactor,
         fontSizeDelta: fontSizeDelta,
       ),
       overline: overline?.apply(
         color: bodyColor,
         decoration: decoration,
         decorationColor: decorationColor,
         decorationStyle: decorationStyle,
         fontFamily: fontFamily,
         fontSizeFactor: fontSizeFactor,
         fontSizeDelta: fontSizeDelta,
       ),
     );
   }

   /// Linearly interpolate between two text themes.
   ///
   /// {@macro flutter.material.themeData.lerp}
   static TextTheme lerp(TextTheme a, TextTheme b, double t) {
     assert(t != null);
     return TextTheme(
       display4: TextStyle.lerp(a?.display4, b?.display4, t),
       display3: TextStyle.lerp(a?.display3, b?.display3, t),
       display2: TextStyle.lerp(a?.display2, b?.display2, t),
       display1: TextStyle.lerp(a?.display1, b?.display1, t),
       headline: TextStyle.lerp(a?.headline, b?.headline, t),
       title: TextStyle.lerp(a?.title, b?.title, t),
       subhead: TextStyle.lerp(a?.subhead, b?.subhead, t),
       body2: TextStyle.lerp(a?.body2, b?.body2, t),
       body1: TextStyle.lerp(a?.body1, b?.body1, t),
       caption: TextStyle.lerp(a?.caption, b?.caption, t),
       button: TextStyle.lerp(a?.button, b?.button, t),
       subtitle: TextStyle.lerp(a?.subtitle, b?.subtitle, t),
       overline: TextStyle.lerp(a?.overline, b?.overline, t),
     );
   }

   @override
   bool operator ==(dynamic other) {
     if (identical(this, other))
       return true;
     if (other.runtimeType != runtimeType)
       return false;
     final TextTheme typedOther = other;
     return display4 == typedOther.display4
         && display3 == typedOther.display3
         && display2 == typedOther.display2
         && display1 == typedOther.display1
         && headline == typedOther.headline
         && title == typedOther.title
         && subhead == typedOther.subhead
         && body2 == typedOther.body2
         && body1 == typedOther.body1
         && caption == typedOther.caption
         && button == typedOther.button
         && subtitle == typedOther.subtitle
         && overline == typedOther.overline;
   }

   @override
   int get hashCode {
     // The hashValues() function supports up to 20 arguments.
     return hashValues(
       display4,
       display3,
       display2,
       display1,
       headline,
       title,
       subhead,
       body2,
       body1,
       caption,
       button,
       subtitle,
       overline,
     );
   }

   @override
   void debugFillProperties(DiagnosticPropertiesBuilder properties) {
     super.debugFillProperties(properties);
     final TextTheme defaultTheme = Typography(platform: defaultTargetPlatform).black;
     properties.add(DiagnosticsProperty<TextStyle>('display4', display4, defaultValue: defaultTheme.display4));
     properties.add(DiagnosticsProperty<TextStyle>('display3', display3, defaultValue: defaultTheme.display3));
     properties.add(DiagnosticsProperty<TextStyle>('display2', display2, defaultValue: defaultTheme.display2));
     properties.add(DiagnosticsProperty<TextStyle>('display1', display1, defaultValue: defaultTheme.display1));
     properties.add(DiagnosticsProperty<TextStyle>('headline', headline, defaultValue: defaultTheme.headline));
     properties.add(DiagnosticsProperty<TextStyle>('title', title, defaultValue: defaultTheme.title));
     properties.add(DiagnosticsProperty<TextStyle>('subhead', subhead, defaultValue: defaultTheme.subhead));
     properties.add(DiagnosticsProperty<TextStyle>('body2', body2, defaultValue: defaultTheme.body2));
     properties.add(DiagnosticsProperty<TextStyle>('body1', body1, defaultValue: defaultTheme.body1));
     properties.add(DiagnosticsProperty<TextStyle>('caption', caption, defaultValue: defaultTheme.caption));
     properties.add(DiagnosticsProperty<TextStyle>('button', button, defaultValue: defaultTheme.button));
     properties.add(DiagnosticsProperty<TextStyle>('subtitle)', subtitle, defaultValue: defaultTheme.subtitle));
     properties.add(DiagnosticsProperty<TextStyle>('overline', overline, defaultValue: defaultTheme.overline));
   }
 }
	// Copyright 2018 The Chromium Authors. All rights reserved.
	// Use of this source code is governed by a BSD-style license that can be
	// found in the LICENSE file.

	import '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 Material Design typography scheme was significantly changed in the
	/// current (2018) version of the specification
	/// (https://material.io/design/typography).
	///
	/// 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 normal 0.0
	/// headline4 34.0 normal 0.25
	/// headline5 24.0 normal 0.0
	/// headline6 20.0 medium 0.15
	/// subtitle1 16.0 normal 0.15
	/// subtitle2 14.0 medium 0.1
	/// body1 16.0 normal 0.5
	/// body2 14.0 normal 0.25
	/// button 14.0 medium 0.75
	/// caption 12.0 normal 0.4
	/// overline 10.0 normal 1.5
	///
	/// ```
	/// Where "light" is `FontWeight.w300`, "normal" is `FontWeight.w400` and
	/// "medium" is `FontWeight.w500`.
	///
	/// The [TextTheme] API is based on the original material (2014)
	/// design spec, which used different text style names. For backwards
	/// compatibility's sake, this API continues to use the original
	/// names. The table below should help with understanding the API in
	/// terms of the 2018 material spec.
	///
	/// Each of the [TextTheme] text styles corresponds to one of the
	/// styles from 2018 spec. By default, the font sizes, font weights
	/// and letter spacings have not changed from their original,
	/// 2014, values.
	/// ```
	/// NAME SIZE WEIGHT SPACING 2018 NAME
	/// display4 112.0 thin 0.0 headline1
	/// display3 56.0 normal 0.0 headline2
	/// display2 45.0 normal 0.0 headline3
	/// display1 34.0 normal 0.0 headline4
	/// headline 24.0 normal 0.0 headline5
	/// title 20.0 medium 0.0 headline6
	/// subhead 16.0 normal 0.0 subtitle1
	/// body2 14.0 medium 0.0 body1
	/// body1 14.0 normal 0.0 body2
	/// caption 12.0 normal 0.0 caption
	/// button 14.0 medium 0.0 button
	/// subtitle 14.0 medium 0.0 subtitle2
	/// overline 10.0 normal 0.0 overline
	/// ```
	///
	/// Where "thin" is `FontWeight.w100`, "normal" is `FontWeight.w400` and
	/// "medium" is `FontWeight.w500`. Letter spacing for all of the original
	/// text styles was 0.0.
	///
	/// To configure a [Theme] for the new sizes, weights, and letter spacings,
	/// initialize its [ThemeData.typography] value with a [Typography] that
	/// object that specifies the 2018 versions of the geometry themes:
	/// [Typography.englishLike2018], [Typography.dense2018],
	/// and [Typography.tall2018].
	///
	/// The following image [from the material design
	/// specification](https://material.io/go/design-typography#typography-styles)
	/// shows the recommended styles for each of the properties of a [TextTheme].
	/// This image uses the `Roboto` font, which is the font used on Android. On
	/// iOS, the [San Francisco
	/// font](https://developer.apple.com/ios/human-interface-guidelines/visual-design/typography/)
	/// is automatically used instead.
	///
	/// ![To see the image, visit the typography site referenced below.](https://storage.googleapis.com/material-design/publish/material_v_11/assets/0Bzhp5Z4wHba3alhXZ2pPWGk3Zjg/style_typography_styles_scale.png)
	///
	/// 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 extends 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].
	const TextTheme({
	this.display4,
	this.display3,
	this.display2,
	this.display1,
	this.headline,
	this.title,
	this.subhead,
	this.body2,
	this.body1,
	this.caption,
	this.button,
	this.subtitle,
	this.overline,
	});

	/// Extremely large text.
	///
	/// The font size is 112 pixels.
	final TextStyle display4;

	/// Very, very large text.
	///
	/// Used for the date in the dialog shown by [showDatePicker].
	final TextStyle display3;

	/// Very large text.
	final TextStyle display2;

	/// Large text.
	final TextStyle display1;

	/// Used for large text in dialogs (e.g., the month and year in the dialog
	/// shown by [showDatePicker]).
	final TextStyle headline;

	/// Used for the primary text in app bars and dialogs (e.g., [AppBar.title]
	/// and [AlertDialog.title]).
	final TextStyle title;

	/// Used for the primary text in lists (e.g., [ListTile.title]).
	final TextStyle subhead;

	/// Used for emphasizing text that would otherwise be [body1].
	final TextStyle body2;

	/// Used for the default text style for [Material].
	final TextStyle body1;

	/// Used for auxiliary text associated with images.
	final TextStyle caption;

	/// Used for text on [RaisedButton] and [FlatButton].
	final TextStyle button;

	/// For medium emphasis text that's a little smaller than [subhead].
	final TextStyle subtitle;

	/// The smallest style,
	///
	/// Typically used for captions or to introduce a (larger) headline.
	final TextStyle overline;

	/// 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 sample}
	///
	/// ```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 {
	/// TitleColorThemeCopy({Key key, this.child, 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(
	/// title: theme.textTheme.title.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 display4,
	TextStyle display3,
	TextStyle display2,
	TextStyle display1,
	TextStyle headline,
	TextStyle title,
	TextStyle subhead,
	TextStyle body2,
	TextStyle body1,
	TextStyle caption,
	TextStyle button,
	TextStyle subtitle,
	TextStyle overline,
	}) {
	return TextTheme(
	display4: display4 ?? this.display4,
	display3: display3 ?? this.display3,
	display2: display2 ?? this.display2,
	display1: display1 ?? this.display1,
	headline: headline ?? this.headline,
	title: title ?? this.title,
	subhead: subhead ?? this.subhead,
	body2: body2 ?? this.body2,
	body1: body1 ?? this.body1,
	caption: caption ?? this.caption,
	button: button ?? this.button,
	subtitle: subtitle ?? this.subtitle,
	overline: overline ?? this.overline,
	);
	}

	/// 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 sample}
	///
	/// ```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 {
	/// TitleColorTheme({Key key, this.child, 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.
	/// TextTheme partialTheme = TextTheme(title: 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(
	display4: display4?.merge(other.display4) ?? other.display4,
	display3: display3?.merge(other.display3) ?? other.display3,
	display2: display2?.merge(other.display2) ?? other.display2,
	display1: display1?.merge(other.display1) ?? other.display1,
	headline: headline?.merge(other.headline) ?? other.headline,
	title: title?.merge(other.title) ?? other.title,
	subhead: subhead?.merge(other.subhead) ?? other.subhead,
	body2: body2?.merge(other.body2) ?? other.body2,
	body1: body1?.merge(other.body1) ?? other.body1,
	caption: caption?.merge(other.caption) ?? other.caption,
	button: button?.merge(other.button) ?? other.button,
	subtitle: subtitle?.merge(other.subtitle) ?? other.subtitle,
	overline: overline?.merge(other.overline) ?? other.overline,
	);
	}

	/// 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 [display4], [display3], [display2],
	/// [display1], and [caption]. 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(
	display4: display4?.apply(
	color: displayColor,
	decoration: decoration,
	decorationColor: decorationColor,
	decorationStyle: decorationStyle,
	fontFamily: fontFamily,
	fontSizeFactor: fontSizeFactor,
	fontSizeDelta: fontSizeDelta,
	),
	display3: display3?.apply(
	color: displayColor,
	decoration: decoration,
	decorationColor: decorationColor,
	decorationStyle: decorationStyle,
	fontFamily: fontFamily,
	fontSizeFactor: fontSizeFactor,
	fontSizeDelta: fontSizeDelta,
	),
	display2: display2?.apply(
	color: displayColor,
	decoration: decoration,
	decorationColor: decorationColor,
	decorationStyle: decorationStyle,
	fontFamily: fontFamily,
	fontSizeFactor: fontSizeFactor,
	fontSizeDelta: fontSizeDelta,
	),
	display1: display1?.apply(
	color: displayColor,
	decoration: decoration,
	decorationColor: decorationColor,
	decorationStyle: decorationStyle,
	fontFamily: fontFamily,
	fontSizeFactor: fontSizeFactor,
	fontSizeDelta: fontSizeDelta,
	),
	headline: headline?.apply(
	color: bodyColor,
	decoration: decoration,
	decorationColor: decorationColor,
	decorationStyle: decorationStyle,
	fontFamily: fontFamily,
	fontSizeFactor: fontSizeFactor,
	fontSizeDelta: fontSizeDelta,
	),
	title: title?.apply(
	color: bodyColor,
	decoration: decoration,
	decorationColor: decorationColor,
	decorationStyle: decorationStyle,
	fontFamily: fontFamily,
	fontSizeFactor: fontSizeFactor,
	fontSizeDelta: fontSizeDelta,
	),
	subhead: subhead?.apply(
	color: bodyColor,
	decoration: decoration,
	decorationColor: decorationColor,
	decorationStyle: decorationStyle,
	fontFamily: fontFamily,
	fontSizeFactor: fontSizeFactor,
	fontSizeDelta: fontSizeDelta,
	),
	body2: body2?.apply(
	color: bodyColor,
	decoration: decoration,
	decorationColor: decorationColor,
	decorationStyle: decorationStyle,
	fontFamily: fontFamily,
	fontSizeFactor: fontSizeFactor,
	fontSizeDelta: fontSizeDelta,
	),
	body1: body1?.apply(
	color: bodyColor,
	decoration: decoration,
	decorationColor: decorationColor,
	decorationStyle: decorationStyle,
	fontFamily: fontFamily,
	fontSizeFactor: fontSizeFactor,
	fontSizeDelta: fontSizeDelta,
	),
	caption: caption?.apply(
	color: displayColor,
	decoration: decoration,
	decorationColor: decorationColor,
	decorationStyle: decorationStyle,
	fontFamily: fontFamily,
	fontSizeFactor: fontSizeFactor,
	fontSizeDelta: fontSizeDelta,
	),
	button: button?.apply(
	color: bodyColor,
	decoration: decoration,
	decorationColor: decorationColor,
	decorationStyle: decorationStyle,
	fontFamily: fontFamily,
	fontSizeFactor: fontSizeFactor,
	fontSizeDelta: fontSizeDelta,
	),
	subtitle: subtitle?.apply(
	color: bodyColor,
	decoration: decoration,
	decorationColor: decorationColor,
	decorationStyle: decorationStyle,
	fontFamily: fontFamily,
	fontSizeFactor: fontSizeFactor,
	fontSizeDelta: fontSizeDelta,
	),
	overline: overline?.apply(
	color: bodyColor,
	decoration: decoration,
	decorationColor: decorationColor,
	decorationStyle: decorationStyle,
	fontFamily: fontFamily,
	fontSizeFactor: fontSizeFactor,
	fontSizeDelta: fontSizeDelta,
	),
	);
	}

	/// Linearly interpolate between two text themes.
	///
	/// {@macro flutter.material.themeData.lerp}
	static TextTheme lerp(TextTheme a, TextTheme b, double t) {
	assert(t != null);
	return TextTheme(
	display4: TextStyle.lerp(a?.display4, b?.display4, t),
	display3: TextStyle.lerp(a?.display3, b?.display3, t),
	display2: TextStyle.lerp(a?.display2, b?.display2, t),
	display1: TextStyle.lerp(a?.display1, b?.display1, t),
	headline: TextStyle.lerp(a?.headline, b?.headline, t),
	title: TextStyle.lerp(a?.title, b?.title, t),
	subhead: TextStyle.lerp(a?.subhead, b?.subhead, t),
	body2: TextStyle.lerp(a?.body2, b?.body2, t),
	body1: TextStyle.lerp(a?.body1, b?.body1, t),
	caption: TextStyle.lerp(a?.caption, b?.caption, t),
	button: TextStyle.lerp(a?.button, b?.button, t),
	subtitle: TextStyle.lerp(a?.subtitle, b?.subtitle, t),
	overline: TextStyle.lerp(a?.overline, b?.overline, t),
	);
	}

	@override
	bool operator ==(dynamic other) {
	if (identical(this, other))
	return true;
	if (other.runtimeType != runtimeType)
	return false;
	final TextTheme typedOther = other;
	return display4 == typedOther.display4
	&& display3 == typedOther.display3
	&& display2 == typedOther.display2
	&& display1 == typedOther.display1
	&& headline == typedOther.headline
	&& title == typedOther.title
	&& subhead == typedOther.subhead
	&& body2 == typedOther.body2
	&& body1 == typedOther.body1
	&& caption == typedOther.caption
	&& button == typedOther.button
	&& subtitle == typedOther.subtitle
	&& overline == typedOther.overline;
	}

	@override
	int get hashCode {
	// The hashValues() function supports up to 20 arguments.
	return hashValues(
	display4,
	display3,
	display2,
	display1,
	headline,
	title,
	subhead,
	body2,
	body1,
	caption,
	button,
	subtitle,
	overline,
	);
	}

	@override
	void debugFillProperties(DiagnosticPropertiesBuilder properties) {
	super.debugFillProperties(properties);
	final TextTheme defaultTheme = Typography(platform: defaultTargetPlatform).black;
	properties.add(DiagnosticsProperty<TextStyle>('display4', display4, defaultValue: defaultTheme.display4));
	properties.add(DiagnosticsProperty<TextStyle>('display3', display3, defaultValue: defaultTheme.display3));
	properties.add(DiagnosticsProperty<TextStyle>('display2', display2, defaultValue: defaultTheme.display2));
	properties.add(DiagnosticsProperty<TextStyle>('display1', display1, defaultValue: defaultTheme.display1));
	properties.add(DiagnosticsProperty<TextStyle>('headline', headline, defaultValue: defaultTheme.headline));
	properties.add(DiagnosticsProperty<TextStyle>('title', title, defaultValue: defaultTheme.title));
	properties.add(DiagnosticsProperty<TextStyle>('subhead', subhead, defaultValue: defaultTheme.subhead));
	properties.add(DiagnosticsProperty<TextStyle>('body2', body2, defaultValue: defaultTheme.body2));
	properties.add(DiagnosticsProperty<TextStyle>('body1', body1, defaultValue: defaultTheme.body1));
	properties.add(DiagnosticsProperty<TextStyle>('caption', caption, defaultValue: defaultTheme.caption));
	properties.add(DiagnosticsProperty<TextStyle>('button', button, defaultValue: defaultTheme.button));
	properties.add(DiagnosticsProperty<TextStyle>('subtitle)', subtitle, defaultValue: defaultTheme.subtitle));
	properties.add(DiagnosticsProperty<TextStyle>('overline', overline, defaultValue: defaultTheme.overline));
	}
	}