Support theming `CupertinoSwitch`s (#116510)

* Introduce flag to maximally apply CupertinoTheme

* add missing docs

* add tests

* fix docs

* fix test

examples/api/lib/material/switch/switch.3.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.
+
+/// Flutter code sample for [Switch].
+import 'package:flutter/cupertino.dart';
+import 'package:flutter/material.dart';
+
+void main() => runApp(const SwitchApp());
+
+class SwitchApp extends StatelessWidget {
+  const SwitchApp({super.key});
+
+  @override
+  Widget build(BuildContext context) {
+    return MaterialApp(
+      theme: ThemeData.light(useMaterial3: true).copyWith(
+        // Use the ambient [CupetinoThemeData] to style all widgets which would
+        // otherwise use iOS defaults.
+        cupertinoOverrideTheme: const CupertinoThemeData(applyThemeToAll: true),
+      ),
+      home: Scaffold(
+        appBar: AppBar(title: const Text('Switch Sample')),
+        body: const Center(
+          child: SwitchExample(),
+        ),
+      ),
+    );
+  }
+}
+
+class SwitchExample extends StatefulWidget {
+  const SwitchExample({super.key});
+
+  @override
+  State<SwitchExample> createState() => _SwitchExampleState();
+}
+
+class _SwitchExampleState extends State<SwitchExample> {
+  bool light = true;
+
+  @override
+  Widget build(BuildContext context) {
+    return Column(
+      mainAxisAlignment: MainAxisAlignment.center,
+      children: <Widget>[
+        Switch.adaptive(
+          value: light,
+          onChanged: (bool value) {
+            setState(() {
+              light = value;
+            });
+          },
+        ),
+        Switch.adaptive(
+          // Don't use the ambient [CupetinoThemeData] to style this switch.
+          applyCupertinoTheme: false,
+          value: light,
+          onChanged: (bool value) {
+            setState(() {
+              light = value;
+            });
+          },
+        ),
+      ],
+    );
+  }
+}

examples/api/test/material/switch/switch.1_test.dart

@@ -3,7 +3,7 @@
 // found in the LICENSE file.
 
 import 'package:flutter/material.dart';
-import 'package:flutter_api_samples/material/switch/switch.0.dart' as example;
+import 'package:flutter_api_samples/material/switch/switch.1.dart' as example;
 import 'package:flutter_test/flutter_test.dart';
 
 void main() {

examples/api/test/material/switch/switch.3_test.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/material.dart';
+import 'package:flutter_api_samples/material/switch/switch.3.dart' as example;
+import 'package:flutter_test/flutter_test.dart';
+
+void main() {
+  testWidgets('Can toggle switch', (WidgetTester tester) async {
+    await tester.pumpWidget(
+      const example.SwitchApp(),
+    );
+
+    final Finder switchFinder = find.byType(Switch).first;
+    Switch materialSwitch = tester.widget<Switch>(switchFinder);
+    expect(materialSwitch.value, true);
+
+    await tester.tap(switchFinder);
+    await tester.pumpAndSettle();
+    materialSwitch = tester.widget<Switch>(switchFinder);
+    expect(materialSwitch.value, false);
+  });
+}

packages/flutter/lib/src/cupertino/switch.dart

@@ -14,6 +14,7 @@ import 'package:flutter/services.dart';
 import 'package:flutter/widgets.dart';
 
 import 'colors.dart';
+import 'theme.dart';
 import 'thumb_painter.dart';
 
 // Examples can assume:
@@ -72,6 +73,7 @@ class CupertinoSwitch extends StatefulWidget {
     this.activeColor,
     this.trackColor,
     this.thumbColor,
+    this.applyTheme,
     this.dragStartBehavior = DragStartBehavior.start,
   }) : assert(value != null),
        assert(dragStartBehavior != null);
@@ -105,13 +107,15 @@ class CupertinoSwitch extends StatefulWidget {
   /// ```
   final ValueChanged<bool>? onChanged;
 
-  /// The color to use when this switch is on.
+  /// The color to use for the track when the switch is on.
   ///
-  /// Defaults to [CupertinoColors.systemGreen] when null and ignores
-  /// the [CupertinoTheme] in accordance to native iOS behavior.
+  /// If null and [applyTheme] is false, defaults to [CupertinoColors.systemGreen]
+  /// in accordance to native iOS behavior. Otherwise, defaults to
+  /// [CupertinoThemeData.primaryColor].
   final Color? activeColor;
 
-  /// The color to use for the background when the switch is off.
+
+  /// The color to use for the track when the switch is off.
   ///
   /// Defaults to [CupertinoColors.secondarySystemFill] when null.
   final Color? trackColor;
@@ -121,6 +125,16 @@ class CupertinoSwitch extends StatefulWidget {
   /// Defaults to [CupertinoColors.white] when null.
   final Color? thumbColor;
 
+  /// {@template flutter.cupertino.CupertinoSwitch.applyTheme}
+  /// Whether to apply the ambient [CupertinoThemeData].
+  ///
+  /// If true, the track uses [CupertinoThemeData.primaryColor] for the track
+  /// when the switch is on.
+  ///
+  /// Defaults to [CupertinoThemeData.applyThemeToAll].
+  /// {@endtemplate}
+  final bool? applyTheme;
+
   /// {@template flutter.cupertino.CupertinoSwitch.dragStartBehavior}
   /// Determines the way that drag start behavior is handled.
   ///
@@ -310,6 +324,7 @@ class _CupertinoSwitchState extends State<CupertinoSwitch> with TickerProviderSt
 
   @override
   Widget build(BuildContext context) {
+    final CupertinoThemeData theme = CupertinoTheme.of(context);
     if (needsPositionAnimation) {
       _resumePositionAnimation();
     }
@@ -320,7 +335,9 @@ class _CupertinoSwitchState extends State<CupertinoSwitch> with TickerProviderSt
         child: _CupertinoSwitchRenderObjectWidget(
           value: widget.value,
           activeColor: CupertinoDynamicColor.resolve(
-            widget.activeColor ?? CupertinoColors.systemGreen,
+            widget.activeColor
+            ?? ((widget.applyTheme ?? theme.applyThemeToAll) ? theme.primaryColor : null)
+            ?? CupertinoColors.systemGreen,
             context,
           ),
           trackColor: CupertinoDynamicColor.resolve(widget.trackColor ?? CupertinoColors.secondarySystemFill, context),

packages/flutter/lib/src/cupertino/theme.dart

@@ -22,6 +22,7 @@ const _CupertinoThemeDefaults _kDefaultTheme = _CupertinoThemeDefaults(
     // Values extracted from navigation bar. For toolbar or tabbar the dark color is 0xF0161616.
   ),
   CupertinoColors.systemBackground,
+  false,
   _CupertinoTextThemeDefaults(CupertinoColors.label, CupertinoColors.inactiveGray),
 );
 
@@ -172,6 +173,7 @@ class CupertinoThemeData extends NoDefaultCupertinoThemeData with Diagnosticable
     CupertinoTextThemeData? textTheme,
     Color? barBackgroundColor,
     Color? scaffoldBackgroundColor,
+    bool? applyThemeToAll,
   }) : this.raw(
         brightness,
         primaryColor,
@@ -179,6 +181,7 @@ class CupertinoThemeData extends NoDefaultCupertinoThemeData with Diagnosticable
         textTheme,
         barBackgroundColor,
         scaffoldBackgroundColor,
+        applyThemeToAll,
       );
 
   /// Same as the default constructor but with positional arguments to avoid
@@ -193,6 +196,7 @@ class CupertinoThemeData extends NoDefaultCupertinoThemeData with Diagnosticable
     CupertinoTextThemeData? textTheme,
     Color? barBackgroundColor,
     Color? scaffoldBackgroundColor,
+    bool? applyThemeToAll,
   ) : this._rawWithDefaults(
     brightness,
     primaryColor,
@@ -200,6 +204,7 @@ class CupertinoThemeData extends NoDefaultCupertinoThemeData with Diagnosticable
     textTheme,
     barBackgroundColor,
     scaffoldBackgroundColor,
+    applyThemeToAll,
     _kDefaultTheme,
   );
 
@@ -210,6 +215,7 @@ class CupertinoThemeData extends NoDefaultCupertinoThemeData with Diagnosticable
     CupertinoTextThemeData? textTheme,
     Color? barBackgroundColor,
     Color? scaffoldBackgroundColor,
+    bool? applyThemeToAll,
     this._defaults,
   ) : super(
     brightness: brightness,
@@ -218,6 +224,7 @@ class CupertinoThemeData extends NoDefaultCupertinoThemeData with Diagnosticable
     textTheme: textTheme,
     barBackgroundColor: barBackgroundColor,
     scaffoldBackgroundColor: scaffoldBackgroundColor,
+    applyThemeToAll: applyThemeToAll,
   );
 
   final _CupertinoThemeDefaults _defaults;
@@ -239,6 +246,9 @@ class CupertinoThemeData extends NoDefaultCupertinoThemeData with Diagnosticable
   @override
   Color get scaffoldBackgroundColor => super.scaffoldBackgroundColor ?? _defaults.scaffoldBackgroundColor;
 
+  @override
+  bool get applyThemeToAll => super.applyThemeToAll ?? _defaults.applyThemeToAll;
+
   @override
   NoDefaultCupertinoThemeData noDefault() {
     return NoDefaultCupertinoThemeData(
@@ -248,6 +258,7 @@ class CupertinoThemeData extends NoDefaultCupertinoThemeData with Diagnosticable
       textTheme: super.textTheme,
       barBackgroundColor: super.barBackgroundColor,
       scaffoldBackgroundColor: super.scaffoldBackgroundColor,
+      applyThemeToAll: super.applyThemeToAll,
     );
   }
 
@@ -262,6 +273,7 @@ class CupertinoThemeData extends NoDefaultCupertinoThemeData with Diagnosticable
       super.textTheme?.resolveFrom(context),
       convertColor(super.barBackgroundColor),
       convertColor(super.scaffoldBackgroundColor),
+      applyThemeToAll,
       _defaults.resolveFrom(context, super.textTheme == null),
     );
   }
@@ -274,6 +286,7 @@ class CupertinoThemeData extends NoDefaultCupertinoThemeData with Diagnosticable
     CupertinoTextThemeData? textTheme,
     Color? barBackgroundColor,
     Color? scaffoldBackgroundColor,
+    bool? applyThemeToAll,
   }) {
     return CupertinoThemeData._rawWithDefaults(
       brightness ?? super.brightness,
@@ -282,6 +295,7 @@ class CupertinoThemeData extends NoDefaultCupertinoThemeData with Diagnosticable
       textTheme ?? super.textTheme,
       barBackgroundColor ?? super.barBackgroundColor,
       scaffoldBackgroundColor ?? super.scaffoldBackgroundColor,
+      applyThemeToAll ?? super.applyThemeToAll,
       _defaults,
     );
   }
@@ -295,6 +309,7 @@ class CupertinoThemeData extends NoDefaultCupertinoThemeData with Diagnosticable
     properties.add(createCupertinoColorProperty('primaryContrastingColor', primaryContrastingColor, defaultValue: defaultData.primaryContrastingColor));
     properties.add(createCupertinoColorProperty('barBackgroundColor', barBackgroundColor, defaultValue: defaultData.barBackgroundColor));
     properties.add(createCupertinoColorProperty('scaffoldBackgroundColor', scaffoldBackgroundColor, defaultValue: defaultData.scaffoldBackgroundColor));
+    properties.add(DiagnosticsProperty<bool>('applyThemeToAll', applyThemeToAll, defaultValue: defaultData.applyThemeToAll));
     textTheme.debugFillProperties(properties);
   }
 }
@@ -322,6 +337,7 @@ class NoDefaultCupertinoThemeData {
     this.textTheme,
     this.barBackgroundColor,
     this.scaffoldBackgroundColor,
+    this.applyThemeToAll,
   });
 
   /// The brightness override for Cupertino descendants.
@@ -389,6 +405,22 @@ class NoDefaultCupertinoThemeData {
   /// Defaults to [CupertinoColors.systemBackground].
   final Color? scaffoldBackgroundColor;
 
+  /// Flag to apply this theme to all descendant Cupertino widgets.
+  ///
+  /// Certain Cupertino widgets previously didn't use theming, matching past
+  /// versions of iOS. For example, [CupertinoSwitch]s always used
+  /// [CupertinoColors.systemGreen] when active.
+  ///
+  /// Today, however, these widgets can indeed be themed on iOS. Moreover on
+  /// macOS, the accent color is reflected in these widgets. Turning this flag
+  /// on ensures that descendant Cupertino widgets will be themed accordingly.
+  ///
+  /// This flag currently applies to the following widgets:
+  /// - [CupertinoSwitch] & [Switch.adaptive]
+  ///
+  /// Defaults to false.
+  final bool? applyThemeToAll;
+
   /// Returns an instance of the theme data whose property getters only return
   /// the construction time specifications with no derived values.
   ///
@@ -412,6 +444,7 @@ class NoDefaultCupertinoThemeData {
       textTheme: textTheme?.resolveFrom(context),
       barBackgroundColor: convertColor(barBackgroundColor),
       scaffoldBackgroundColor: convertColor(scaffoldBackgroundColor),
+      applyThemeToAll: applyThemeToAll,
     );
   }
 
@@ -428,6 +461,7 @@ class NoDefaultCupertinoThemeData {
     CupertinoTextThemeData? textTheme,
     Color? barBackgroundColor ,
     Color? scaffoldBackgroundColor,
+    bool? applyThemeToAll,
   }) {
     return NoDefaultCupertinoThemeData(
       brightness: brightness ?? this.brightness,
@@ -436,6 +470,7 @@ class NoDefaultCupertinoThemeData {
       textTheme: textTheme ?? this.textTheme,
       barBackgroundColor: barBackgroundColor ?? this.barBackgroundColor,
       scaffoldBackgroundColor: scaffoldBackgroundColor ?? this.scaffoldBackgroundColor,
+      applyThemeToAll: applyThemeToAll ?? this.applyThemeToAll,
     );
   }
 }
@@ -448,6 +483,7 @@ class _CupertinoThemeDefaults {
     this.primaryContrastingColor,
     this.barBackgroundColor,
     this.scaffoldBackgroundColor,
+    this.applyThemeToAll,
     this.textThemeDefaults,
   );
 
@@ -456,6 +492,7 @@ class _CupertinoThemeDefaults {
   final Color primaryContrastingColor;
   final Color barBackgroundColor;
   final Color scaffoldBackgroundColor;
+  final bool applyThemeToAll;
   final _CupertinoTextThemeDefaults textThemeDefaults;
 
   _CupertinoThemeDefaults resolveFrom(BuildContext context, bool resolveTextTheme) {
@@ -467,6 +504,7 @@ class _CupertinoThemeDefaults {
       convertColor(primaryContrastingColor),
       convertColor(barBackgroundColor),
       convertColor(scaffoldBackgroundColor),
+      applyThemeToAll,
       resolveTextTheme ? textThemeDefaults.resolveFrom(context) : textThemeDefaults,
     );
   }

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

@@ -117,6 +117,7 @@ class Switch extends StatelessWidget {
     this.onFocusChange,
     this.autofocus = false,
   })  : _switchType = _SwitchType.material,
+        applyCupertinoTheme = false,
         assert(dragStartBehavior != null),
         assert(activeThumbImage != null || onActiveThumbImageError == null),
         assert(inactiveThumbImage != null || onInactiveThumbImageError == null);
@@ -161,6 +162,7 @@ class Switch extends StatelessWidget {
     this.focusNode,
     this.onFocusChange,
     this.autofocus = false,
+    this.applyCupertinoTheme,
   })  : assert(autofocus != null),
         assert(activeThumbImage != null || onActiveThumbImageError == null),
         assert(inactiveThumbImage != null || onInactiveThumbImageError == null),
@@ -381,6 +383,9 @@ class Switch extends StatelessWidget {
 
   final _SwitchType _switchType;
 
+  /// {@macro flutter.cupertino.CupertinoSwitch.applyTheme}
+  final bool? applyCupertinoTheme;
+
   /// {@macro flutter.cupertino.CupertinoSwitch.dragStartBehavior}
   final DragStartBehavior dragStartBehavior;
 
@@ -495,6 +500,7 @@ class Switch extends StatelessWidget {
           onChanged: onChanged,
           activeColor: activeColor,
           trackColor: inactiveTrackColor,
+          applyTheme: applyCupertinoTheme,
         ),
       ),
     );

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

@@ -2703,6 +2703,7 @@ class MaterialBasedCupertinoThemeData extends CupertinoThemeData {
         _cupertinoOverrideTheme.textTheme,
         _cupertinoOverrideTheme.barBackgroundColor,
         _cupertinoOverrideTheme.scaffoldBackgroundColor,
+        _cupertinoOverrideTheme.applyThemeToAll,
       );
 
   final ThemeData _materialTheme;
@@ -2738,6 +2739,7 @@ class MaterialBasedCupertinoThemeData extends CupertinoThemeData {
     CupertinoTextThemeData? textTheme,
     Color? barBackgroundColor,
     Color? scaffoldBackgroundColor,
+    bool? applyThemeToAll,
   }) {
     return MaterialBasedCupertinoThemeData._(
       _materialTheme,
@@ -2748,6 +2750,7 @@ class MaterialBasedCupertinoThemeData extends CupertinoThemeData {
         textTheme: textTheme,
         barBackgroundColor: barBackgroundColor,
         scaffoldBackgroundColor: scaffoldBackgroundColor,
+        applyThemeToAll: applyThemeToAll,
       ),
     );
   }

packages/flutter/test/cupertino/switch_test.dart

@@ -764,6 +764,66 @@ void main() {
     );
   });
 
+  testWidgets('Switch can apply the ambient theme and be opted out', (WidgetTester tester) async {
+    final Key switchKey = UniqueKey();
+    bool value = false;
+    await tester.pumpWidget(
+      CupertinoTheme(
+        data: const CupertinoThemeData(primaryColor: Colors.amber, applyThemeToAll: true),
+        child: Directionality(
+          textDirection: TextDirection.ltr,
+          child: StatefulBuilder(
+            builder: (BuildContext context, StateSetter setState) {
+              return Center(
+                child: RepaintBoundary(
+                  child: Column(
+                    children: <Widget>[
+                      CupertinoSwitch(
+                        key: switchKey,
+                        value: value,
+                        dragStartBehavior: DragStartBehavior.down,
+                        applyTheme: true,
+                        onChanged: (bool newValue) {
+                          setState(() {
+                            value = newValue;
+                          });
+                        },
+                      ),
+                      CupertinoSwitch(
+                        value: value,
+                        dragStartBehavior: DragStartBehavior.down,
+                        applyTheme: false,
+                        onChanged: (bool newValue) {
+                          setState(() {
+                            value = newValue;
+                          });
+                        },
+                      ),
+                    ],
+                  ),
+                ),
+              );
+            },
+          ),
+        ),
+      ),
+    );
+
+    await expectLater(
+      find.byType(Column),
+      matchesGoldenFile('switch.tap.off.themed.png'),
+    );
+
+    await tester.tap(find.byKey(switchKey));
+    expect(value, isTrue);
+
+    await tester.pumpAndSettle();
+    await expectLater(
+      find.byType(Column),
+      matchesGoldenFile('switch.tap.on.themed.png'),
+    );
+  });
+
   testWidgets('Hovering over Cupertino switch updates cursor to clickable on Web', (WidgetTester tester) async {
     const bool value = false;
     // Disabled CupertinoSwitch does not update cursor on Web.

packages/flutter/test/cupertino/theme_test.dart

@@ -52,6 +52,7 @@ void main() {
     expect(theme.brightness, isNull);
     expect(theme.primaryColor, CupertinoColors.activeBlue);
     expect(theme.textTheme.textStyle.fontSize, 17.0);
+    expect(theme.applyThemeToAll, false);
   });
 
   testWidgets('Theme attributes cascade', (WidgetTester tester) async {
@@ -122,10 +123,12 @@ void main() {
     (WidgetTester tester) async {
       const CupertinoThemeData originalTheme = CupertinoThemeData(
         brightness: Brightness.dark,
+        applyThemeToAll: true,
       );
 
       final CupertinoThemeData theme = await testTheme(tester, originalTheme.copyWith(
         primaryColor: CupertinoColors.systemGreen,
+        applyThemeToAll: false,
       ));
 
       expect(theme.brightness, Brightness.dark);
@@ -133,6 +136,8 @@ void main() {
       // Now check calculated derivatives.
       expect(theme.textTheme.actionTextStyle.color, isSameColorAs(CupertinoColors.systemGreen.darkColor));
       expect(theme.scaffoldBackgroundColor, isSameColorAs(CupertinoColors.black));
+
+      expect(theme.applyThemeToAll, false);
     },
   );
 
@@ -181,6 +186,7 @@ void main() {
           'primaryContrastingColor',
           'barBackgroundColor',
           'scaffoldBackgroundColor',
+          'applyThemeToAll',
           'textStyle',
           'actionTextStyle',
           'tabLabelTextStyle',