Reland: Adds support for the Material Badge widget, BadgeTheme, Badge…

…ThemeData (#114560) (#115002)

Requires G3Fix cl/486997831

dev/tools/gen_defaults/bin/gen_defaults.dart

@@ -19,6 +19,7 @@ import 'dart:io';
 
 import 'package:gen_defaults/action_chip_template.dart';
 import 'package:gen_defaults/app_bar_template.dart';
+import 'package:gen_defaults/badge_template.dart';
 import 'package:gen_defaults/banner_template.dart';
 import 'package:gen_defaults/bottom_app_bar_template.dart';
 import 'package:gen_defaults/bottom_sheet_template.dart';
@@ -54,6 +55,7 @@ Future<void> main(List<String> args) async {
   const List<String> tokenFiles = <String>[
     'badge.json',
     'banner.json',
+    'badge.json',
     'bottom_app_bar.json',
     'button_elevated.json',
     'button_filled.json',
@@ -125,6 +127,8 @@ Future<void> main(List<String> args) async {
   ActionChipTemplate('Chip', '$materialLib/chip.dart', tokens).updateFile();
   ActionChipTemplate('ActionChip', '$materialLib/action_chip.dart', tokens).updateFile();
   AppBarTemplate('AppBar', '$materialLib/app_bar.dart', tokens).updateFile();
+  BottomAppBarTemplate('BottomAppBar', '$materialLib/bottom_app_bar.dart', tokens).updateFile();
+  BadgeTemplate('Badge', '$materialLib/badge.dart', tokens).updateFile();
   BannerTemplate('Banner', '$materialLib/banner.dart', tokens).updateFile();
   BottomAppBarTemplate('BottomAppBar', '$materialLib/bottom_app_bar.dart', tokens).updateFile();
   BottomSheetTemplate('BottomSheet', '$materialLib/bottom_sheet.dart', tokens).updateFile();

dev/tools/gen_defaults/lib/badge_template.dart

@@ -0,0 +1,36 @@
+// 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 'template.dart';
+
+class BadgeTemplate extends TokenTemplate {
+  const BadgeTemplate(super.blockName, super.fileName, super.tokens, {
+    super.colorSchemePrefix = '_colors.',
+  });
+
+  @override
+  String generate() => '''
+class _${blockName}DefaultsM3 extends BadgeThemeData {
+  _${blockName}DefaultsM3(this.context) : super(
+    smallSize: ${tokens["md.comp.badge.size"]},
+    largeSize: ${tokens["md.comp.badge.large.size"]},
+    padding: const EdgeInsets.symmetric(horizontal: 4),
+    alignment: const AlignmentDirectional(12, -4),
+  );
+
+  final BuildContext context;
+  late final ThemeData _theme = Theme.of(context);
+  late final ColorScheme _colors = _theme.colorScheme;
+
+  @override
+  Color? get backgroundColor => ${color("md.comp.badge.color")};
+
+  @override
+  Color? get textColor => ${color("md.comp.badge.large.label-text.color")};
+
+  @override
+  TextStyle? get textStyle => ${textStyle("md.comp.badge.large.label-text")};
+}
+''';
+}

packages/flutter/lib/material.dart

@@ -30,6 +30,8 @@ export 'src/material/app_bar_theme.dart';
 export 'src/material/arc.dart';
 export 'src/material/autocomplete.dart';
 export 'src/material/back_button.dart';
+export 'src/material/badge.dart';
+export 'src/material/badge_theme.dart';
 export 'src/material/banner.dart';
 export 'src/material/banner_theme.dart';
 export 'src/material/bottom_app_bar.dart';

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

@@ -0,0 +1,190 @@
+// 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/widgets.dart';
+
+import 'badge_theme.dart';
+import 'color_scheme.dart';
+import 'theme.dart';
+
+/// A Material Design "badge".
+///
+/// A badge's [label] conveys a small amount of information about its
+/// [child], like a count or status. If the label is null then this is
+/// a "small" badge that's displayed as a [smallSize] diameter filled
+/// circle. Otherwise this is a [StadiumBorder] shaped "large" badge
+/// with height [largeSize].
+///
+/// Badges are typically used to decorate the icon within a
+/// BottomNavigationBarItem] or a [NavigationRailDestination]
+/// or a button's icon, as in [TextButton.icon]. The badge's default
+/// configuration is intended to work well with a default sized (24)
+/// [Icon].
+class Badge extends StatelessWidget {
+  /// Create a Badge that stacks [label] on top of [child].
+  ///
+  /// If [label] is null then just a filled circle is displayed. Otherwise
+  /// the [label] is displayed within a [StadiumBorder] shaped area.
+  const Badge({
+    super.key,
+    this.backgroundColor,
+    this.textColor,
+    this.smallSize,
+    this.largeSize,
+    this.textStyle,
+    this.padding,
+    this.alignment,
+    this.label,
+    this.child,
+  });
+
+  /// The badge's fill color.
+  ///
+  /// Defaults to the [BadgeTheme]'s background color, or
+  /// [ColorScheme.errorColor] if the theme value is null.
+  final Color? backgroundColor;
+
+  /// The color of the badge's [label] text.
+  ///
+  /// This color overrides the color of the label's [textStyle].
+  ///
+  /// Defaults to the [BadgeTheme]'s foreground color, or
+  /// [ColorScheme.onError] if the theme value is null.
+  final Color? textColor;
+
+  /// The diameter of the badge if [label] is null.
+  ///
+  /// Defaults to the [BadgeTheme]'s small size, or 6 if the theme value
+  /// is null.
+  final double? smallSize;
+
+  /// The badge's height if [label] is non-null.
+  ///
+  /// Defaults to the [BadgeTheme]'s large size, or 16 if the theme value
+  /// is null. If the default value is overridden then it may be useful to
+  /// also override [padding] and [alignment].
+  final double? largeSize;
+
+  /// The [DefaultTextStyle] for the badge's label.
+  ///
+  /// The text style's color is overwritten by the [textColor].
+  ///
+  /// This value is only used if [label] is non-null.
+  ///
+  /// Defaults to the [BadgeTheme]'s text style, or the overall theme's
+  /// [TextTheme.labelSmall] if the badge theme's value is null. If
+  /// the default text style is overridden then it may be useful to
+  /// also override [largeSize], [padding], and [alignment].
+  final TextStyle? textStyle;
+
+  /// The padding added to the badge's label.
+  ///
+  /// This value is only used if [label] is non-null.
+  ///
+  /// Defaults to the [BadgeTheme]'s padding, or 4 pixels on the
+  /// left and right if the theme's value is null.
+  final EdgeInsetsGeometry? padding;
+
+  /// The location of the [label] relative to the [child].
+  ///
+  /// This value is only used if [label] is non-null.
+  ///
+  /// Defaults to the [BadgeTheme]'s alignment, or `start = 12`
+  /// and `top = -4` if the theme's value is null.
+  final AlignmentDirectional? alignment;
+
+  /// The badge's content, typically a [Text] widget that contains 1 to 4
+  /// characters.
+  ///
+  /// If the label is null then this is a "small" badge that's
+  /// displayed as a [smallSize] diameter filled circle. Otherwise
+  /// this is a [StadiumBorder] shaped "large" badge with height [largeSize].
+  final Widget? label;
+
+  /// The widget that the badge is stacked on top of.
+  ///
+  /// Typically this is an default sized [Icon] that's part of a
+  /// [BottomNavigationBarItem] or a [NavigationRailDestination].
+  final Widget? child;
+
+  @override
+  Widget build(BuildContext context) {
+    final BadgeThemeData badgeTheme = BadgeTheme.of(context);
+    final BadgeThemeData defaults = _BadgeDefaultsM3(context);
+    final double effectiveSmallSize = smallSize ?? badgeTheme.smallSize ?? defaults.smallSize!;
+    final double effectiveLargeSize = largeSize ?? badgeTheme.largeSize ?? defaults.largeSize!;
+
+    final Widget badge = DefaultTextStyle(
+      style: (textStyle ?? badgeTheme.textStyle ?? defaults.textStyle!).copyWith(
+        color: textColor ?? badgeTheme.textColor ?? defaults.textColor!,
+      ),
+      child: IntrinsicWidth(
+        child: Container(
+          height: label == null ? effectiveSmallSize : effectiveLargeSize,
+          clipBehavior: Clip.antiAlias,
+          decoration: ShapeDecoration(
+            color: backgroundColor ?? badgeTheme.backgroundColor ?? defaults.backgroundColor!,
+            shape: const StadiumBorder(),
+          ),
+          padding: label == null ? null : (padding ?? badgeTheme.padding ?? defaults.padding!),
+          alignment: label == null ? null : Alignment.center,
+          child: label ?? SizedBox(width: effectiveSmallSize, height: effectiveSmallSize),
+        ),
+      ),
+    );
+
+    if (child == null) {
+      return badge;
+    }
+
+    final AlignmentDirectional effectiveAlignment = alignment ?? badgeTheme.alignment ?? defaults.alignment!;
+    return
+      Stack(
+        clipBehavior: Clip.none,
+        children: <Widget>[
+          child!,
+          Positioned.directional(
+            textDirection: Directionality.of(context),
+            start: label == null ? null : effectiveAlignment.start,
+            end: label == null ? 0 : null,
+            top: label == null ? 0 : effectiveAlignment.y,
+            child: badge,
+          ),
+        ],
+      );
+  }
+}
+
+// BEGIN GENERATED TOKEN PROPERTIES - Badge
+
+// Do not edit by hand. The code between the "BEGIN GENERATED" and
+// "END GENERATED" comments are generated from data in the Material
+// Design token database by the script:
+//   dev/tools/gen_defaults/bin/gen_defaults.dart.
+
+// Token database version: v0_137
+
+class _BadgeDefaultsM3 extends BadgeThemeData {
+  _BadgeDefaultsM3(this.context) : super(
+    smallSize: 6.0,
+    largeSize: 16.0,
+    padding: const EdgeInsets.symmetric(horizontal: 4),
+    alignment: const AlignmentDirectional(12, -4),
+  );
+
+  final BuildContext context;
+  late final ThemeData _theme = Theme.of(context);
+  late final ColorScheme _colors = _theme.colorScheme;
+
+  @override
+  Color? get backgroundColor => _colors.error;
+
+  @override
+  Color? get textColor => _colors.onError;
+
+  @override
+  TextStyle? get textStyle => Theme.of(context).textTheme.labelSmall;
+}
+
+// END GENERATED TOKEN PROPERTIES - Badge