// 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.
///
/// 
///
/// 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));
}
}