packages/flutter/lib/src/cupertino/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/widgets.dart';

import 'colors.dart';

// Please update _TextThemeDefaultsBuilder accordingly after changing the default
// color here, as their implementation depends on the default value of the color
// field.
//
// Values derived from https://developer.apple.com/design/resources/.
const TextStyle _kDefaultTextStyle = TextStyle(
  inherit: false,
  fontFamily: '.SF Pro Text',
  fontSize: 17.0,
  letterSpacing: -0.41,
  color: CupertinoColors.label,
  decoration: TextDecoration.none,
);

// Please update _TextThemeDefaultsBuilder accordingly after changing the default
// color here, as their implementation depends on the default value of the color
// field.
//
// Values derived from https://developer.apple.com/design/resources/.
const TextStyle _kDefaultActionTextStyle = TextStyle(
  inherit: false,
  fontFamily: '.SF Pro Text',
  fontSize: 17.0,
  letterSpacing: -0.41,
  color: CupertinoColors.activeBlue,
  decoration: TextDecoration.none,
);

// Please update _TextThemeDefaultsBuilder accordingly after changing the default
// color here, as their implementation depends on the default value of the color
// field.
//
// Values derived from https://developer.apple.com/design/resources/.
const TextStyle _kDefaultTabLabelTextStyle = TextStyle(
  inherit: false,
  fontFamily: '.SF Pro Text',
  fontSize: 10.0,
  fontWeight: FontWeight.w500,
  letterSpacing: -0.24,
  color: CupertinoColors.inactiveGray,
);

const TextStyle _kDefaultMiddleTitleTextStyle = TextStyle(
  inherit: false,
  fontFamily: '.SF Pro Text',
  fontSize: 17.0,
  fontWeight: FontWeight.w600,
  letterSpacing: -0.41,
  color: CupertinoColors.label,
);

const TextStyle _kDefaultLargeTitleTextStyle = TextStyle(
  inherit: false,
  fontFamily: '.SF Pro Display',
  fontSize: 34.0,
  fontWeight: FontWeight.w700,
  letterSpacing: 0.41,
  color: CupertinoColors.label,
);

// Please update _TextThemeDefaultsBuilder accordingly after changing the default
// color here, as their implementation depends on the default value of the color
// field.
//
// Inspected on iOS 13 simulator with "Debug View Hierarchy".
// Value extracted from off-center labels. Centered labels have a font size of 25pt.
//
// The letterSpacing sourced from iOS 14 simulator screenshots for comparison.
// See also:
//
// * https://github.com/flutter/flutter/pull/65501#discussion_r486557093
const TextStyle _kDefaultPickerTextStyle = TextStyle(
  inherit: false,
  fontFamily: '.SF Pro Display',
  fontSize: 21.0,
  fontWeight: FontWeight.w400,
  letterSpacing: -0.6,
  color: CupertinoColors.label,
);

// Please update _TextThemeDefaultsBuilder accordingly after changing the default
// color here, as their implementation depends on the default value of the color
// field.
//
// Inspected on iOS 13 simulator with "Debug View Hierarchy".
// Value extracted from off-center labels. Centered labels have a font size of 25pt.
const TextStyle _kDefaultDateTimePickerTextStyle = TextStyle(
  inherit: false,
  fontFamily: '.SF Pro Display',
  fontSize: 21,
  fontWeight: FontWeight.normal,
  color: CupertinoColors.label,
);

TextStyle? _resolveTextStyle(TextStyle? style, BuildContext context) {
  // This does not resolve the shadow color, foreground, background, etc.
  return style?.copyWith(
    color: CupertinoDynamicColor.maybeResolve(style.color, context),
    backgroundColor: CupertinoDynamicColor.maybeResolve(style.backgroundColor, context),
    decorationColor: CupertinoDynamicColor.maybeResolve(style.decorationColor, context),
  );
}

/// Cupertino typography theme in a [CupertinoThemeData].
@immutable
class CupertinoTextThemeData with Diagnosticable {
  /// Create a [CupertinoTextThemeData].
  ///
  /// The [primaryColor] is used to derive TextStyle defaults of other attributes
  /// such as [navActionTextStyle] and [actionTextStyle], it must not be null when
  /// either [navActionTextStyle] or [actionTextStyle] is null. Defaults to
  /// [CupertinoColors.systemBlue].
  ///
  /// Other [TextStyle] parameters default to default iOS text styles when
  /// unspecified.
  const CupertinoTextThemeData({
    Color primaryColor = CupertinoColors.systemBlue,
    TextStyle? textStyle,
    TextStyle? actionTextStyle,
    TextStyle? tabLabelTextStyle,
    TextStyle? navTitleTextStyle,
    TextStyle? navLargeTitleTextStyle,
    TextStyle? navActionTextStyle,
    TextStyle? pickerTextStyle,
    TextStyle? dateTimePickerTextStyle,
  }) : this._raw(
         const _TextThemeDefaultsBuilder(CupertinoColors.label, CupertinoColors.inactiveGray),
         primaryColor,
         textStyle,
         actionTextStyle,
         tabLabelTextStyle,
         navTitleTextStyle,
         navLargeTitleTextStyle,
         navActionTextStyle,
         pickerTextStyle,
         dateTimePickerTextStyle,
       );

  const CupertinoTextThemeData._raw(
    this._defaults,
    this._primaryColor,
    this._textStyle,
    this._actionTextStyle,
    this._tabLabelTextStyle,
    this._navTitleTextStyle,
    this._navLargeTitleTextStyle,
    this._navActionTextStyle,
    this._pickerTextStyle,
    this._dateTimePickerTextStyle,
  ) : assert((_navActionTextStyle != null && _actionTextStyle != null) || _primaryColor != null);

  final _TextThemeDefaultsBuilder _defaults;
  final Color? _primaryColor;

  final TextStyle? _textStyle;
  /// The [TextStyle] of general text content for Cupertino widgets.
  TextStyle get textStyle => _textStyle ?? _defaults.textStyle;

  final TextStyle? _actionTextStyle;
  /// The [TextStyle] of interactive text content such as text in a button without background.
  TextStyle get actionTextStyle {
    return _actionTextStyle ?? _defaults.actionTextStyle(primaryColor: _primaryColor);
  }

  final TextStyle? _tabLabelTextStyle;
  /// The [TextStyle] of unselected tabs.
  TextStyle get tabLabelTextStyle => _tabLabelTextStyle ?? _defaults.tabLabelTextStyle;

  final TextStyle? _navTitleTextStyle;
  /// The [TextStyle] of titles in standard navigation bars.
  TextStyle get navTitleTextStyle => _navTitleTextStyle ?? _defaults.navTitleTextStyle;

  final TextStyle? _navLargeTitleTextStyle;
  /// The [TextStyle] of large titles in sliver navigation bars.
  TextStyle get navLargeTitleTextStyle => _navLargeTitleTextStyle ?? _defaults.navLargeTitleTextStyle;

  final TextStyle? _navActionTextStyle;
  /// The [TextStyle] of interactive text content in navigation bars.
  TextStyle get navActionTextStyle {
    return _navActionTextStyle ?? _defaults.navActionTextStyle(primaryColor: _primaryColor);
  }

  final TextStyle? _pickerTextStyle;
  /// The [TextStyle] of pickers.
  TextStyle get pickerTextStyle => _pickerTextStyle ?? _defaults.pickerTextStyle;

  final TextStyle? _dateTimePickerTextStyle;
  /// The [TextStyle] of date time pickers.
  TextStyle get dateTimePickerTextStyle => _dateTimePickerTextStyle ?? _defaults.dateTimePickerTextStyle;

  /// Returns a copy of the current [CupertinoTextThemeData] with all the colors
  /// resolved against the given [BuildContext].
  ///
  /// If any of the [InheritedWidget]s required to resolve this
  /// [CupertinoTextThemeData] is not found in [context], any unresolved
  /// [CupertinoDynamicColor]s will use the default trait value
  /// ([Brightness.light] platform brightness, normal contrast,
  /// [CupertinoUserInterfaceLevelData.base] elevation level).
  CupertinoTextThemeData resolveFrom(BuildContext context) {
    return CupertinoTextThemeData._raw(
      _defaults.resolveFrom(context),
      CupertinoDynamicColor.maybeResolve(_primaryColor, context),
      _resolveTextStyle(_textStyle, context),
      _resolveTextStyle(_actionTextStyle, context),
      _resolveTextStyle(_tabLabelTextStyle, context),
      _resolveTextStyle(_navTitleTextStyle, context),
      _resolveTextStyle(_navLargeTitleTextStyle, context),
      _resolveTextStyle(_navActionTextStyle, context),
      _resolveTextStyle(_pickerTextStyle, context),
      _resolveTextStyle(_dateTimePickerTextStyle, context),
    );
  }

  /// Returns a copy of the current [CupertinoTextThemeData] instance with
  /// specified overrides.
  CupertinoTextThemeData copyWith({
    Color? primaryColor,
    TextStyle? textStyle,
    TextStyle? actionTextStyle,
    TextStyle? tabLabelTextStyle,
    TextStyle? navTitleTextStyle,
    TextStyle? navLargeTitleTextStyle,
    TextStyle? navActionTextStyle,
    TextStyle? pickerTextStyle,
    TextStyle? dateTimePickerTextStyle,
  }) {
    return CupertinoTextThemeData._raw(
      _defaults,
      primaryColor ?? _primaryColor,
      textStyle ?? _textStyle,
      actionTextStyle ?? _actionTextStyle,
      tabLabelTextStyle ?? _tabLabelTextStyle,
      navTitleTextStyle ?? _navTitleTextStyle,
      navLargeTitleTextStyle ?? _navLargeTitleTextStyle,
      navActionTextStyle ?? _navActionTextStyle,
      pickerTextStyle ?? _pickerTextStyle,
      dateTimePickerTextStyle ?? _dateTimePickerTextStyle,
    );
  }

  @override
  void debugFillProperties(DiagnosticPropertiesBuilder properties) {
    super.debugFillProperties(properties);
    const CupertinoTextThemeData defaultData = CupertinoTextThemeData();
    properties.add(DiagnosticsProperty<TextStyle>('textStyle', textStyle, defaultValue: defaultData.textStyle));
    properties.add(DiagnosticsProperty<TextStyle>('actionTextStyle', actionTextStyle, defaultValue: defaultData.actionTextStyle));
    properties.add(DiagnosticsProperty<TextStyle>('tabLabelTextStyle', tabLabelTextStyle, defaultValue: defaultData.tabLabelTextStyle));
    properties.add(DiagnosticsProperty<TextStyle>('navTitleTextStyle', navTitleTextStyle, defaultValue: defaultData.navTitleTextStyle));
    properties.add(DiagnosticsProperty<TextStyle>('navLargeTitleTextStyle', navLargeTitleTextStyle, defaultValue: defaultData.navLargeTitleTextStyle));
    properties.add(DiagnosticsProperty<TextStyle>('navActionTextStyle', navActionTextStyle, defaultValue: defaultData.navActionTextStyle));
    properties.add(DiagnosticsProperty<TextStyle>('pickerTextStyle', pickerTextStyle, defaultValue: defaultData.pickerTextStyle));
    properties.add(DiagnosticsProperty<TextStyle>('dateTimePickerTextStyle', dateTimePickerTextStyle, defaultValue: defaultData.dateTimePickerTextStyle));
  }
}


@immutable
class _TextThemeDefaultsBuilder {
  const _TextThemeDefaultsBuilder(
    this.labelColor,
    this.inactiveGrayColor,
  ) : assert(labelColor != null),
      assert(inactiveGrayColor != null);

  final Color labelColor;
  final Color inactiveGrayColor;

  static TextStyle _applyLabelColor(TextStyle original, Color color) {
    return original.color == color
      ?  original
      :  original.copyWith(color: color);
  }

  TextStyle get textStyle => _applyLabelColor(_kDefaultTextStyle, labelColor);
  TextStyle get tabLabelTextStyle => _applyLabelColor(_kDefaultTabLabelTextStyle, inactiveGrayColor);
  TextStyle get navTitleTextStyle => _applyLabelColor(_kDefaultMiddleTitleTextStyle, labelColor);
  TextStyle get navLargeTitleTextStyle => _applyLabelColor(_kDefaultLargeTitleTextStyle, labelColor);
  TextStyle get pickerTextStyle => _applyLabelColor(_kDefaultPickerTextStyle, labelColor);
  TextStyle get dateTimePickerTextStyle => _applyLabelColor(_kDefaultDateTimePickerTextStyle, labelColor);

  TextStyle actionTextStyle({ Color? primaryColor }) => _kDefaultActionTextStyle.copyWith(color: primaryColor);
  TextStyle navActionTextStyle({ Color? primaryColor }) => actionTextStyle(primaryColor: primaryColor);

  _TextThemeDefaultsBuilder resolveFrom(BuildContext context) {
    final Color resolvedLabelColor = CupertinoDynamicColor.resolve(labelColor, context);
    final Color resolvedInactiveGray = CupertinoDynamicColor.resolve(inactiveGrayColor, context);
    return resolvedLabelColor == labelColor && resolvedInactiveGray == CupertinoColors.inactiveGray
      ? this
      : _TextThemeDefaultsBuilder(resolvedLabelColor, resolvedInactiveGray);
  }
}