chip_theme.dart

// 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 'dart:ui' show lerpDouble;

import 'package:flutter/foundation.dart';
import 'package:flutter/rendering.dart';
import 'package:flutter/widgets.dart';

import 'colors.dart';
import 'theme.dart';
import 'theme_data.dart';

/// Applies a chip theme to descendant [RawChip]-based widgets, like [Chip],
/// [InputChip], [ChoiceChip], [FilterChip], and [ActionChip].
///
/// A chip theme describes the color, shape and text styles for the chips it is
/// applied to
///
/// Descendant widgets obtain the current theme's [ChipThemeData] object using
/// [ChipTheme.of]. When a widget uses [ChipTheme.of], it is automatically
/// rebuilt if the theme later changes.
///
/// The [ThemeData] object given by the [Theme.of] call also contains a default
/// [Theme.chipTheme] that can be customized by copying it (using
/// [ChipThemeData.copyWith]).
///
/// See also:
///
///  * [Chip], a chip that displays information and can be deleted.
///  * [InputChip], a chip that represents a complex piece of information, such
///    as an entity (person, place, or thing) or conversational text, in a
///    compact form.
///  * [ChoiceChip], allows a single selection from a set of options. Choice
///    chips contain related descriptive text or categories.
///  * [FilterChip], uses tags or descriptive words as a way to filter content.
///  * [ActionChip], represents an action related to primary content.
///  * [ChipThemeData], which describes the actual configuration of a chip
///    theme.
///  * [ThemeData], which describes the overall theme information for the
///    application.
class ChipTheme extends InheritedTheme {
  /// Applies the given theme [data] to [child].
  ///
  /// The [data] and [child] arguments must not be null.
  const ChipTheme({
    Key key,
    @required this.data,
    @required Widget child,
  }) : assert(child != null),
       assert(data != null),
       super(key: key, child: child);

  /// Specifies the color, shape, and text style values for descendant chip
  /// widgets.
  final ChipThemeData data;

  /// Returns the data from the closest [ChipTheme] instance that encloses
  /// the given context.
  ///
  /// Defaults to the ambient [ThemeData.chipTheme] if there is no
  /// [ChipTheme] in the given build context.
  ///
  /// {@tool sample}
  ///
  /// ```dart
  /// class Spaceship extends StatelessWidget {
  ///   @override
  ///   Widget build(BuildContext context) {
  ///     return ChipTheme(
  ///       data: ChipTheme.of(context).copyWith(backgroundColor: Colors.red),
  ///       child: ActionChip(
  ///         label: const Text('Launch'),
  ///         onPressed: () { print('We have liftoff!'); },
  ///       ),
  ///     );
  ///   }
  /// }
  /// ```
  /// {@end-tool}
  ///
  /// See also:
  ///
  ///  * [ChipThemeData], which describes the actual configuration of a chip
  ///    theme.
  static ChipThemeData of(BuildContext context) {
    final ChipTheme inheritedTheme = context.inheritFromWidgetOfExactType(ChipTheme);
    return inheritedTheme?.data ?? Theme.of(context).chipTheme;
  }

  @override
  Widget wrap(BuildContext context, Widget child) {
    final ChipTheme ancestorTheme = context.ancestorWidgetOfExactType(ChipTheme);
    return identical(this, ancestorTheme) ? child : ChipTheme(data: data, child: child);
  }

  @override
  bool updateShouldNotify(ChipTheme oldWidget) => data != oldWidget.data;
}

/// Holds the color, shape, and text styles for a material design chip theme.
///
/// Use this class to configure a [ChipTheme] widget, or to set the
/// [ThemeData.chipTheme] for a [Theme] widget.
///
/// To obtain the current ambient chip theme, use [ChipTheme.of].
///
/// The parts of a chip are:
///
///  * The "avatar", which is a widget that appears at the beginning of the
///    chip. This is typically a [CircleAvatar] widget.
///  * The "label", which is the widget displayed in the center of the chip.
///    Typically this is a [Text] widget.
///  * The "delete icon", which is a widget that appears at the end of the chip.
///  * The chip is disabled when it is not accepting user input. Only some chips
///    have a disabled state: [InputChip], [ChoiceChip], and [FilterChip].
///
/// The simplest way to create a ChipThemeData is to use [copyWith] on the one
/// you get from [ChipTheme.of], or create an entirely new one with
/// [ChipThemeData..fromDefaults].
///
/// {@tool sample}
///
/// ```dart
/// class CarColor extends StatefulWidget {
///   @override
///   State createState() => _CarColorState();
/// }
///
/// class _CarColorState extends State<CarColor> {
///   Color _color = Colors.red;
///
///   @override
///   Widget build(BuildContext context) {
///     return ChipTheme(
///       data: ChipTheme.of(context).copyWith(backgroundColor: Colors.lightBlue),
///       child: ChoiceChip(
///         label: Text('Light Blue'),
///         onSelected: (bool value) {
///           setState(() {
///             _color = value ? Colors.lightBlue : Colors.red;
///           });
///         },
///         selected: _color == Colors.lightBlue,
///       ),
///     );
///   }
/// }
/// ```
/// {@end-tool}
///
/// See also:
///
///  * [Chip], a chip that displays information and can be deleted.
///  * [InputChip], a chip that represents a complex piece of information, such
///    as an entity (person, place, or thing) or conversational text, in a
///    compact form.
///  * [ChoiceChip], allows a single selection from a set of options. Choice
///    chips contain related descriptive text or categories.
///  * [FilterChip], uses tags or descriptive words as a way to filter content.
///  * [ActionChip], represents an action related to primary content.
///  * [CircleAvatar], which shows images or initials of entities.
///  * [Wrap], A widget that displays its children in multiple horizontal or
///    vertical runs.
///  * [ChipTheme] widget, which can override the chip theme of its
///    children.
///  * [Theme] widget, which performs a similar function to [ChipTheme],
///    but for overall themes.
///  * [ThemeData], which has a default [ChipThemeData].
class ChipThemeData extends Diagnosticable {
  /// Create a [ChipThemeData] given a set of exact values. All the values
  /// must be specified except for [shadowColor], [selectedShadowColor],
  /// [elevation], and [pressElevation], which may be null.
  ///
  /// This will rarely be used directly. It is used by [lerp] to
  /// create intermediate themes based on two themes.
  const ChipThemeData({
    @required this.backgroundColor,
    this.deleteIconColor,
    @required this.disabledColor,
    @required this.selectedColor,
    @required this.secondarySelectedColor,
    this.shadowColor,
    this.selectedShadowColor,
    this.showCheckmark,
    this.checkmarkColor,
    @required this.labelPadding,
    @required this.padding,
    @required this.shape,
    @required this.labelStyle,
    @required this.secondaryLabelStyle,
    @required this.brightness,
    this.elevation,
    this.pressElevation,
  }) : assert(backgroundColor != null),
       assert(disabledColor != null),
       assert(selectedColor != null),
       assert(secondarySelectedColor != null),
       assert(labelPadding != null),
       assert(padding != null),
       assert(shape != null),
       assert(labelStyle != null),
       assert(secondaryLabelStyle != null),
       assert(brightness != null);

  /// Generates a ChipThemeData from a brightness, a primary color, and a text
  /// style.
  ///
  /// The [brightness] is used to select a primary color from the default
  /// values.
  ///
  /// The optional [primaryColor] is used as the base color for the other
  /// colors. The opacity of the [primaryColor] is ignored. If a [primaryColor]
  /// is specified, then the [brightness] is ignored, and the theme brightness
  /// is determined from the [primaryColor].
  ///
  /// Only one of [primaryColor] or [brightness] may be specified.
  ///
  /// The [secondaryColor] is used for the selection colors needed by
  /// [ChoiceChip].
  ///
  /// This is used to generate the default chip theme for a [ThemeData].
  factory ChipThemeData.fromDefaults({
    Brightness brightness,
    Color primaryColor,
    @required Color secondaryColor,
    @required TextStyle labelStyle,
  }) {
    assert(primaryColor != null || brightness != null,
      'One of primaryColor or brightness must be specified');
    assert(primaryColor == null || brightness == null,
      'Only one of primaryColor or brightness may be specified');
    assert(secondaryColor != null);
    assert(labelStyle != null);

    if (primaryColor != null) {
      brightness = ThemeData.estimateBrightnessForColor(primaryColor);
    }

    // These are Material Design defaults, and are used to derive
    // component Colors (with opacity) from base colors.
    const int backgroundAlpha = 0x1f; // 12%
    const int deleteIconAlpha = 0xde; // 87%
    const int disabledAlpha = 0x0c; // 38% * 12% = 5%
    const int selectAlpha = 0x3d; // 12% + 12% = 24%
    const int textLabelAlpha = 0xde; // 87%
    const ShapeBorder shape = StadiumBorder();
    const EdgeInsetsGeometry labelPadding = EdgeInsets.symmetric(horizontal: 8.0);
    const EdgeInsetsGeometry padding = EdgeInsets.all(4.0);

    primaryColor = primaryColor ?? (brightness == Brightness.light ? Colors.black : Colors.white);
    final Color backgroundColor = primaryColor.withAlpha(backgroundAlpha);
    final Color deleteIconColor = primaryColor.withAlpha(deleteIconAlpha);
    final Color disabledColor = primaryColor.withAlpha(disabledAlpha);
    final Color selectedColor = primaryColor.withAlpha(selectAlpha);
    final Color secondarySelectedColor = secondaryColor.withAlpha(selectAlpha);
    final TextStyle secondaryLabelStyle = labelStyle.copyWith(
      color: secondaryColor.withAlpha(textLabelAlpha),
    );
    labelStyle = labelStyle.copyWith(color: primaryColor.withAlpha(textLabelAlpha));

    return ChipThemeData(
      backgroundColor: backgroundColor,
      deleteIconColor: deleteIconColor,
      disabledColor: disabledColor,
      selectedColor: selectedColor,
      secondarySelectedColor: secondarySelectedColor,
      labelPadding: labelPadding,
      padding: padding,
      shape: shape,
      labelStyle: labelStyle,
      secondaryLabelStyle: secondaryLabelStyle,
      brightness: brightness,
    );
  }

  /// Color to be used for the unselected, enabled chip's background.
  ///
  /// The default is light grey.
  final Color backgroundColor;

  /// The [Color] for the delete icon. The default is Color(0xde000000)
  /// (slightly transparent black) for light themes, and Color(0xdeffffff)
  /// (slightly transparent white) for dark themes.
  ///
  /// May be set to null, in which case the ambient [IconTheme.color] is used.
  final Color deleteIconColor;

  /// Color to be used for the chip's background indicating that it is disabled.
  ///
  /// The chip is disabled when [isEnabled] is false, or all three of
  /// [SelectableChipAttributes.onSelected], [TappableChipAttributes.onPressed],
  /// and [DeletableChipAttributes.onDelete] are null.
  ///
  /// It defaults to [Colors.black38].
  final Color disabledColor;

  /// Color to be used for the chip's background, indicating that it is
  /// selected.
  ///
  /// The chip is selected when [selected] is true.
  final Color selectedColor;

  /// An alternate color to be used for the chip's background, indicating that
  /// it is selected. For example, this color is used by [ChoiceChip] when the
  /// choice is selected.
  ///
  /// The chip is selected when [selected] is true.
  final Color secondarySelectedColor;

  /// Color of the chip's shadow when the elevation is greater than 0.
  ///
  /// If null, the chip defaults to [Colors.black].
  ///
  /// See also:
  ///
  ///  * [selectedShadowColor]
  final Color shadowColor;

  /// Color of the chip's shadow when the elevation is greater than 0 and the
  /// chip is selected.
  ///
  /// If null, the chip defaults to [Colors.black].
  ///
  /// See also:
  ///
  ///  * [shadowColor]
  final Color selectedShadowColor;

  /// Whether or not to show a check mark when [selected] is true.
  ///
  /// For instance, the [ChoiceChip] sets this to false so that it can be
  /// selected without showing the check mark.
  ///
  /// Defaults to true.
  final bool showCheckmark;

  /// Color of the chip's check mark when a check mark is visible.
  ///
  /// This will override the color set by the platform's brightness setting.
  final Color checkmarkColor;

  /// The padding around the [label] widget.
  ///
  /// By default, this is 4 logical pixels at the beginning and the end of the
  /// label, and zero on top and bottom.
  final EdgeInsetsGeometry labelPadding;

  /// The padding between the contents of the chip and the outside [shape].
  ///
  /// Defaults to 4 logical pixels on all sides.
  final EdgeInsetsGeometry padding;

  /// The border to draw around the chip.
  ///
  /// Defaults to a [StadiumBorder]. Must not be null.
  final ShapeBorder shape;

  /// The style to be applied to the chip's label.
  ///
  /// This only has an effect on label widgets that respect the
  /// [DefaultTextStyle], such as [Text].
  final TextStyle labelStyle;

  /// An alternate style to be applied to the chip's label. For example, this
  /// style is applied to the text of a selected [ChoiceChip].
  ///
  /// This only has an effect on label widgets that respect the
  /// [DefaultTextStyle], such as [Text].
  final TextStyle secondaryLabelStyle;

  /// The brightness setting for this theme.
  ///
  /// This affects various base material color choices in the chip rendering.
  final Brightness brightness;

  /// The elevation to be applied to the chip.
  ///
  /// If null, the chip defaults to 0.
  final double elevation;

  /// The elevation to be applied to the chip during the press motion.
  ///
  /// If null, the chip defaults to 8.
  final double pressElevation;

  /// Creates a copy of this object but with the given fields replaced with the
  /// new values.
  ChipThemeData copyWith({
    Color backgroundColor,
    Color deleteIconColor,
    Color disabledColor,
    Color selectedColor,
    Color secondarySelectedColor,
    Color shadowColor,
    Color selectedShadowColor,
    Color checkmarkColor,
    EdgeInsetsGeometry labelPadding,
    EdgeInsetsGeometry padding,
    ShapeBorder shape,
    TextStyle labelStyle,
    TextStyle secondaryLabelStyle,
    Brightness brightness,
    double elevation,
    double pressElevation,
  }) {
    return ChipThemeData(
      backgroundColor: backgroundColor ?? this.backgroundColor,
      deleteIconColor: deleteIconColor ?? this.deleteIconColor,
      disabledColor: disabledColor ?? this.disabledColor,
      selectedColor: selectedColor ?? this.selectedColor,
      secondarySelectedColor: secondarySelectedColor ?? this.secondarySelectedColor,
      shadowColor: shadowColor ?? this.shadowColor,
      selectedShadowColor: selectedShadowColor ?? this.selectedShadowColor,
      checkmarkColor: checkmarkColor ?? this.checkmarkColor,
      labelPadding: labelPadding ?? this.labelPadding,
      padding: padding ?? this.padding,
      shape: shape ?? this.shape,
      labelStyle: labelStyle ?? this.labelStyle,
      secondaryLabelStyle: secondaryLabelStyle ?? this.secondaryLabelStyle,
      brightness: brightness ?? this.brightness,
      elevation: elevation ?? this.elevation,
      pressElevation: pressElevation ?? this.pressElevation,
    );
  }

  /// Linearly interpolate between two chip themes.
  ///
  /// The arguments must not be null.
  ///
  /// {@macro dart.ui.shadow.lerp}
  static ChipThemeData lerp(ChipThemeData a, ChipThemeData b, double t) {
    assert(t != null);
    if (a == null && b == null)
      return null;
    return ChipThemeData(
      backgroundColor: Color.lerp(a?.backgroundColor, b?.backgroundColor, t),
      deleteIconColor: Color.lerp(a?.deleteIconColor, b?.deleteIconColor, t),
      disabledColor: Color.lerp(a?.disabledColor, b?.disabledColor, t),
      selectedColor: Color.lerp(a?.selectedColor, b?.selectedColor, t),
      secondarySelectedColor: Color.lerp(a?.secondarySelectedColor, b?.secondarySelectedColor, t),
      shadowColor: Color.lerp(a?.shadowColor, b?.shadowColor, t),
      selectedShadowColor: Color.lerp(a?.selectedShadowColor, b?.selectedShadowColor, t),
      checkmarkColor: Color.lerp(a?.checkmarkColor, b?.checkmarkColor, t),
      labelPadding: EdgeInsetsGeometry.lerp(a?.labelPadding, b?.labelPadding, t),
      padding: EdgeInsetsGeometry.lerp(a?.padding, b?.padding, t),
      shape: ShapeBorder.lerp(a?.shape, b?.shape, t),
      labelStyle: TextStyle.lerp(a?.labelStyle, b?.labelStyle, t),
      secondaryLabelStyle: TextStyle.lerp(a?.secondaryLabelStyle, b?.secondaryLabelStyle, t),
      brightness: t < 0.5 ? a?.brightness ?? Brightness.light : b?.brightness ?? Brightness.light,
      elevation: lerpDouble(a?.elevation, b?.elevation, t),
      pressElevation: lerpDouble(a?.pressElevation, b?.pressElevation, t),
    );
  }

  @override
  int get hashCode {
    return hashValues(
      backgroundColor,
      deleteIconColor,
      disabledColor,
      selectedColor,
      secondarySelectedColor,
      shadowColor,
      selectedShadowColor,
      checkmarkColor,
      labelPadding,
      padding,
      shape,
      labelStyle,
      secondaryLabelStyle,
      brightness,
      elevation,
      pressElevation,
    );
  }

  @override
  bool operator ==(Object other) {
    if (identical(this, other)) {
      return true;
    }
    if (other.runtimeType != runtimeType) {
      return false;
    }
    final ChipThemeData otherData = other;
    return otherData.backgroundColor == backgroundColor
        && otherData.deleteIconColor == deleteIconColor
        && otherData.disabledColor == disabledColor
        && otherData.selectedColor == selectedColor
        && otherData.secondarySelectedColor == secondarySelectedColor
        && otherData.shadowColor == shadowColor
        && otherData.selectedShadowColor == selectedShadowColor
        && otherData.checkmarkColor == checkmarkColor
        && otherData.labelPadding == labelPadding
        && otherData.padding == padding
        && otherData.shape == shape
        && otherData.labelStyle == labelStyle
        && otherData.secondaryLabelStyle == secondaryLabelStyle
        && otherData.brightness == brightness
        && otherData.elevation == elevation
        && otherData.pressElevation == pressElevation;
  }

  @override
  void debugFillProperties(DiagnosticPropertiesBuilder properties) {
    super.debugFillProperties(properties);
    final ThemeData defaultTheme = ThemeData.fallback();
    final ChipThemeData defaultData = ChipThemeData.fromDefaults(
      secondaryColor: defaultTheme.primaryColor,
      brightness: defaultTheme.brightness,
      labelStyle: defaultTheme.textTheme.body2,
    );
    properties.add(ColorProperty('backgroundColor', backgroundColor, defaultValue: defaultData.backgroundColor));
    properties.add(ColorProperty('deleteIconColor', deleteIconColor, defaultValue: defaultData.deleteIconColor));
    properties.add(ColorProperty('disabledColor', disabledColor, defaultValue: defaultData.disabledColor));
    properties.add(ColorProperty('selectedColor', selectedColor, defaultValue: defaultData.selectedColor));
    properties.add(ColorProperty('secondarySelectedColor', secondarySelectedColor, defaultValue: defaultData.secondarySelectedColor));
    properties.add(ColorProperty('shadowColor', shadowColor, defaultValue: defaultData.shadowColor));
    properties.add(ColorProperty('selectedShadowColor', selectedShadowColor, defaultValue: defaultData.selectedShadowColor));
    properties.add(ColorProperty('checkMarkColor', checkmarkColor, defaultValue: defaultData.checkmarkColor));
    properties.add(DiagnosticsProperty<EdgeInsetsGeometry>('labelPadding', labelPadding, defaultValue: defaultData.labelPadding));
    properties.add(DiagnosticsProperty<EdgeInsetsGeometry>('padding', padding, defaultValue: defaultData.padding));
    properties.add(DiagnosticsProperty<ShapeBorder>('shape', shape, defaultValue: defaultData.shape));
    properties.add(DiagnosticsProperty<TextStyle>('labelStyle', labelStyle, defaultValue: defaultData.labelStyle));
    properties.add(DiagnosticsProperty<TextStyle>('secondaryLabelStyle', secondaryLabelStyle, defaultValue: defaultData.secondaryLabelStyle));
    properties.add(EnumProperty<Brightness>('brightness', brightness, defaultValue: defaultData.brightness));
    properties.add(DoubleProperty('elevation', elevation, defaultValue: defaultData.elevation));
    properties.add(DoubleProperty('pressElevation', pressElevation, defaultValue: defaultData.pressElevation));
  }
}