[material_ui] Add global Material style variant

packages/material_ui/lib/src/app_bar.dart

@@ -906,6 +906,8 @@ class _AppBarState extends State<AppBar> {
     final ThemeData theme = Theme.of(context);
     final IconButtonThemeData iconButtonTheme = IconButtonTheme.of(context);
     final AppBarThemeData appBarTheme = AppBarTheme.of(context);
+    final StyleVariant effectiveVariant = appBarTheme.variant ?? theme.variant;
+    assert(effectiveVariant != .material3Expressive, kUnsupportedStyleVariantAssertionMessage);
     final AppBarThemeData defaults = theme.useMaterial3
         ? _AppBarDefaultsM3(context)
         : _AppBarDefaultsM2(context);

packages/material_ui/lib/src/app_bar_theme.dart

@@ -11,6 +11,7 @@ import 'package:flutter/foundation.dart';
 import 'package:flutter/services.dart';
 import 'package:flutter/widgets.dart';
 
+import 'debug.dart';
 import 'theme.dart';
 
 // Examples can assume:
@@ -410,10 +411,12 @@ class AppBarThemeData with Diagnosticable {
     this.titleTextStyle,
     this.systemOverlayStyle,
     this.actionsPadding,
+    this.variant,
   }) : assert(
          color == null || backgroundColor == null,
          'The color and backgroundColor parameters mean the same thing. Only specify one.',
-       );
+       ),
+       assert(variant != .material3Expressive, kUnsupportedStyleVariantAssertionMessage);
 
   /// Overrides the default value of [AppBar.backgroundColor].
   final Color? backgroundColor;
@@ -466,6 +469,9 @@ class AppBarThemeData with Diagnosticable {
   /// Overrides the default value of [AppBar.actionsPadding].
   final EdgeInsetsGeometry? actionsPadding;
 
+  /// The style variant of Material Design used by [AppBar].
+  final StyleVariant? variant;
+
   /// Creates a copy of this object but with the given fields replaced with the
   /// new values.
   AppBarThemeData copyWith({
@@ -491,6 +497,7 @@ class AppBarThemeData with Diagnosticable {
     TextStyle? titleTextStyle,
     SystemUiOverlayStyle? systemOverlayStyle,
     EdgeInsetsGeometry? actionsPadding,
+    StyleVariant? variant,
   }) {
     return AppBarThemeData(
       backgroundColor: backgroundColor ?? color ?? this.backgroundColor,
@@ -510,6 +517,7 @@ class AppBarThemeData with Diagnosticable {
       titleTextStyle: titleTextStyle ?? this.titleTextStyle,
       systemOverlayStyle: systemOverlayStyle ?? this.systemOverlayStyle,
       actionsPadding: actionsPadding ?? this.actionsPadding,
+      variant: variant ?? this.variant,
     );
   }
 
@@ -538,6 +546,7 @@ class AppBarThemeData with Diagnosticable {
       titleTextStyle: TextStyle.lerp(a.titleTextStyle, b.titleTextStyle, t),
       systemOverlayStyle: t < 0.5 ? a.systemOverlayStyle : b.systemOverlayStyle,
       actionsPadding: EdgeInsetsGeometry.lerp(a.actionsPadding, b.actionsPadding, t),
+      variant: t < 0.5 ? a.variant : b.variant,
     );
   }
 
@@ -560,6 +569,7 @@ class AppBarThemeData with Diagnosticable {
     titleTextStyle,
     systemOverlayStyle,
     actionsPadding,
+    variant,
   );
 
   @override
@@ -587,7 +597,8 @@ class AppBarThemeData with Diagnosticable {
         other.toolbarTextStyle == toolbarTextStyle &&
         other.titleTextStyle == titleTextStyle &&
         other.systemOverlayStyle == systemOverlayStyle &&
-        other.actionsPadding == actionsPadding;
+        other.actionsPadding == actionsPadding &&
+        other.variant == variant;
   }
 
   @override
@@ -633,5 +644,6 @@ class AppBarThemeData with Diagnosticable {
         defaultValue: null,
       ),
     );
+    properties.add(EnumProperty<StyleVariant>('variant', variant, defaultValue: null));
   }
 }

packages/material_ui/lib/src/debug.dart

@@ -11,6 +11,11 @@ import 'scaffold.dart' show Scaffold, ScaffoldMessenger;
 // Examples can assume:
 // late BuildContext context;
 
+/// The assertion message used while Material components do not yet support
+/// Material 3 Expressive.
+const String kUnsupportedStyleVariantAssertionMessage =
+    'Only material3 is supported. See https://github.com/orgs/flutter/projects/250 to track support for material3Expressive.';
+
 /// Asserts that the given context has a [Material] ancestor within the closest
 /// [LookupBoundary].
 ///

packages/material_ui/lib/src/elevated_button.dart

@@ -18,6 +18,7 @@ import 'button_style_button.dart';
 import 'color_scheme.dart';
 import 'colors.dart';
 import 'constants.dart';
+import 'debug.dart';
 import 'elevated_button_theme.dart';
 import 'ink_ripple.dart';
 import 'ink_well.dart';
@@ -392,6 +393,8 @@ class ElevatedButton extends ButtonStyleButton {
   @override
   ButtonStyle defaultStyleOf(BuildContext context) {
     final ThemeData theme = Theme.of(context);
+    final StyleVariant effectiveVariant = ElevatedButtonTheme.of(context).variant ?? theme.variant;
+    assert(effectiveVariant != .material3Expressive, kUnsupportedStyleVariantAssertionMessage);
     final ColorScheme colorScheme = theme.colorScheme;
     final ButtonStyle buttonStyle = theme.useMaterial3
         ? _ElevatedButtonDefaultsM3(context)

packages/material_ui/lib/src/elevated_button_theme.dart

@@ -9,6 +9,7 @@ import 'package:flutter/foundation.dart';
 import 'package:flutter/widgets.dart';
 
 import 'button_style.dart';
+import 'debug.dart';
 import 'theme.dart';
 
 // Examples can assume:
@@ -39,7 +40,8 @@ class ElevatedButtonThemeData with Diagnosticable {
   /// Creates an [ElevatedButtonThemeData].
   ///
   /// The [style] may be null.
-  const ElevatedButtonThemeData({this.style});
+  const ElevatedButtonThemeData({this.style, this.variant})
+    : assert(variant != .material3Expressive, kUnsupportedStyleVariantAssertionMessage);
 
   /// Overrides for [ElevatedButton]'s default style.
   ///
@@ -50,6 +52,9 @@ class ElevatedButtonThemeData with Diagnosticable {
   /// If [style] is null, then this theme doesn't override anything.
   final ButtonStyle? style;
 
+  /// The style variant of Material Design used by [ElevatedButton].
+  final StyleVariant? variant;
+
   /// Linearly interpolate between two elevated button themes.
   static ElevatedButtonThemeData? lerp(
     ElevatedButtonThemeData? a,
@@ -59,11 +64,14 @@ class ElevatedButtonThemeData with Diagnosticable {
     if (identical(a, b)) {
       return a;
     }
-    return ElevatedButtonThemeData(style: ButtonStyle.lerp(a?.style, b?.style, t));
+    return ElevatedButtonThemeData(
+      style: ButtonStyle.lerp(a?.style, b?.style, t),
+      variant: t < 0.5 ? a?.variant : b?.variant,
+    );
   }
 
   @override
-  int get hashCode => style.hashCode;
+  int get hashCode => Object.hash(style, variant);
 
   @override
   bool operator ==(Object other) {
@@ -73,13 +81,14 @@ class ElevatedButtonThemeData with Diagnosticable {
     if (other.runtimeType != runtimeType) {
       return false;
     }
-    return other is ElevatedButtonThemeData && other.style == style;
+    return other is ElevatedButtonThemeData && other.style == style && other.variant == variant;
   }
 
   @override
   void debugFillProperties(DiagnosticPropertiesBuilder properties) {
     super.debugFillProperties(properties);
     properties.add(DiagnosticsProperty<ButtonStyle>('style', style, defaultValue: null));
+    properties.add(EnumProperty<StyleVariant>('variant', variant, defaultValue: null));
   }
 }
 

packages/material_ui/lib/src/filled_button.dart

@@ -19,6 +19,7 @@ import 'button_style_button.dart';
 import 'color_scheme.dart';
 import 'colors.dart';
 import 'constants.dart';
+import 'debug.dart';
 import 'filled_button_theme.dart';
 import 'ink_well.dart';
 import 'material_state.dart';
@@ -430,13 +431,16 @@ class FilledButton extends ButtonStyleButton {
   /// [ButtonStyle.padding] is reduced from 24 to 16.
   @override
   ButtonStyle defaultStyleOf(BuildContext context) {
+    final ThemeData theme = Theme.of(context);
+    final StyleVariant effectiveVariant = FilledButtonTheme.of(context).variant ?? theme.variant;
+    assert(effectiveVariant != .material3Expressive, kUnsupportedStyleVariantAssertionMessage);
     final ButtonStyle buttonStyle = switch (_variant) {
       _FilledButtonVariant.filled => _FilledButtonDefaultsM3(context),
       _FilledButtonVariant.tonal => _FilledTonalButtonDefaultsM3(context),
     };
 
     if (_addPadding) {
-      final bool useMaterial3 = Theme.of(context).useMaterial3;
+      final bool useMaterial3 = theme.useMaterial3;
       final double defaultFontSize =
           buttonStyle.textStyle?.resolve(const <WidgetState>{})?.fontSize ?? 14.0;
       final double effectiveTextScale =

packages/material_ui/lib/src/filled_button_theme.dart

@@ -9,6 +9,7 @@ import 'package:flutter/foundation.dart';
 import 'package:flutter/widgets.dart';
 
 import 'button_style.dart';
+import 'debug.dart';
 import 'theme.dart';
 
 // Examples can assume:
@@ -39,7 +40,8 @@ class FilledButtonThemeData with Diagnosticable {
   /// Creates an [FilledButtonThemeData].
   ///
   /// The [style] may be null.
-  const FilledButtonThemeData({this.style});
+  const FilledButtonThemeData({this.style, this.variant})
+    : assert(variant != .material3Expressive, kUnsupportedStyleVariantAssertionMessage);
 
   /// Overrides for [FilledButton]'s default style.
   ///
@@ -50,16 +52,22 @@ class FilledButtonThemeData with Diagnosticable {
   /// If [style] is null, then this theme doesn't override anything.
   final ButtonStyle? style;
 
+  /// The style variant of Material Design used by [FilledButton].
+  final StyleVariant? variant;
+
   /// Linearly interpolate between two filled button themes.
   static FilledButtonThemeData? lerp(FilledButtonThemeData? a, FilledButtonThemeData? b, double t) {
     if (identical(a, b)) {
       return a;
     }
-    return FilledButtonThemeData(style: ButtonStyle.lerp(a?.style, b?.style, t));
+    return FilledButtonThemeData(
+      style: ButtonStyle.lerp(a?.style, b?.style, t),
+      variant: t < 0.5 ? a?.variant : b?.variant,
+    );
   }
 
   @override
-  int get hashCode => style.hashCode;
+  int get hashCode => Object.hash(style, variant);
 
   @override
   bool operator ==(Object other) {
@@ -69,13 +77,14 @@ class FilledButtonThemeData with Diagnosticable {
     if (other.runtimeType != runtimeType) {
       return false;
     }
-    return other is FilledButtonThemeData && other.style == style;
+    return other is FilledButtonThemeData && other.style == style && other.variant == variant;
   }
 
   @override
   void debugFillProperties(DiagnosticPropertiesBuilder properties) {
     super.debugFillProperties(properties);
     properties.add(DiagnosticsProperty<ButtonStyle>('style', style, defaultValue: null));
+    properties.add(EnumProperty<StyleVariant>('variant', variant, defaultValue: null));
   }
 }
 

packages/material_ui/lib/src/floating_action_button.dart

@@ -15,6 +15,7 @@ import 'package:flutter/widgets.dart';
 
 import 'button.dart';
 import 'color_scheme.dart';
+import 'debug.dart';
 import 'floating_action_button_theme.dart';
 import 'scaffold.dart';
 import 'text_theme.dart';
@@ -491,6 +492,8 @@ class FloatingActionButton extends StatelessWidget {
     final FloatingActionButtonThemeData floatingActionButtonTheme = FloatingActionButtonTheme.of(
       context,
     );
+    final StyleVariant effectiveVariant = floatingActionButtonTheme.variant ?? theme.variant;
+    assert(effectiveVariant != .material3Expressive, kUnsupportedStyleVariantAssertionMessage);
     final FloatingActionButtonThemeData defaults = theme.useMaterial3
         ? _FABDefaultsM3(context, _floatingActionButtonType, child != null)
         : _FABDefaultsM2(context, _floatingActionButtonType, child != null);

packages/material_ui/lib/src/floating_action_button_theme.dart

@@ -15,6 +15,7 @@ import 'package:flutter/foundation.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/widgets.dart';
 
+import 'debug.dart';
 import 'theme.dart';
 
 // Examples can assume:
@@ -64,7 +65,11 @@ class FloatingActionButtonThemeData with Diagnosticable {
     this.extendedPadding,
     this.extendedTextStyle,
     this.mouseCursor,
-  });
+    this.variant,
+  }) : assert(variant != .material3Expressive, kUnsupportedStyleVariantAssertionMessage);
+
+  /// The style variant of Material Design used by [FloatingActionButton].
+  final StyleVariant? variant;
 
   /// Color to be used for the unselected, enabled [FloatingActionButton]'s
   /// foreground.
@@ -171,6 +176,7 @@ class FloatingActionButtonThemeData with Diagnosticable {
     EdgeInsetsGeometry? extendedPadding,
     TextStyle? extendedTextStyle,
     WidgetStateProperty<MouseCursor?>? mouseCursor,
+    StyleVariant? variant,
   }) {
     return FloatingActionButtonThemeData(
       foregroundColor: foregroundColor ?? this.foregroundColor,
@@ -194,6 +200,7 @@ class FloatingActionButtonThemeData with Diagnosticable {
       extendedPadding: extendedPadding ?? this.extendedPadding,
       extendedTextStyle: extendedTextStyle ?? this.extendedTextStyle,
       mouseCursor: mouseCursor ?? this.mouseCursor,
+      variant: variant ?? this.variant,
     );
   }
 
@@ -248,6 +255,7 @@ class FloatingActionButtonThemeData with Diagnosticable {
       extendedPadding: EdgeInsetsGeometry.lerp(a?.extendedPadding, b?.extendedPadding, t),
       extendedTextStyle: TextStyle.lerp(a?.extendedTextStyle, b?.extendedTextStyle, t),
       mouseCursor: t < 0.5 ? a?.mouseCursor : b?.mouseCursor,
+      variant: t < 0.5 ? a?.variant : b?.variant,
     );
   }
 
@@ -272,7 +280,7 @@ class FloatingActionButtonThemeData with Diagnosticable {
     extendedSizeConstraints,
     extendedIconLabelSpacing,
     extendedPadding,
-    Object.hash(extendedTextStyle, mouseCursor),
+    Object.hash(extendedTextStyle, mouseCursor, variant),
   );
 
   @override
@@ -304,7 +312,8 @@ class FloatingActionButtonThemeData with Diagnosticable {
         other.extendedIconLabelSpacing == extendedIconLabelSpacing &&
         other.extendedPadding == extendedPadding &&
         other.extendedTextStyle == extendedTextStyle &&
-        other.mouseCursor == mouseCursor;
+        other.mouseCursor == mouseCursor &&
+        other.variant == variant;
   }
 
   @override
@@ -368,6 +377,7 @@ class FloatingActionButtonThemeData with Diagnosticable {
         defaultValue: null,
       ),
     );
+    properties.add(EnumProperty<StyleVariant>('variant', variant, defaultValue: null));
   }
 }
 

packages/material_ui/lib/src/icon_button.dart

@@ -718,6 +718,9 @@ class IconButton extends StatelessWidget {
     final ThemeData theme = Theme.of(context);
 
     if (theme.useMaterial3) {
+      final StyleVariant effectiveVariant = IconButtonTheme.of(context).variant ?? theme.variant;
+      assert(effectiveVariant != .material3Expressive, kUnsupportedStyleVariantAssertionMessage);
+
       final Size? minSize = constraints == null
           ? null
           : Size(constraints!.minWidth, constraints!.minHeight);