Let SnackBar inherit themeData from its ancestor (#70080)

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

@@ -460,9 +460,7 @@ class _SnackBarState extends State<SnackBar> {
     final Color themeBackgroundColor = isThemeDark
       ? colorScheme.onSurface
       : Color.alphaBlend(colorScheme.onSurface.withOpacity(0.80), colorScheme.surface);
-    final ThemeData inverseTheme = ThemeData(
-      brightness: brightness,
-      backgroundColor: themeBackgroundColor,
+    final ThemeData inverseTheme = theme.copyWith(
       colorScheme: ColorScheme(
         primary: colorScheme.onPrimary,
         primaryVariant: colorScheme.onPrimary,
@@ -480,10 +478,9 @@ class _SnackBarState extends State<SnackBar> {
         onError: colorScheme.error,
         brightness: brightness,
       ),
-      snackBarTheme: snackBarTheme,
     );
 
-    final TextStyle? contentTextStyle = snackBarTheme.contentTextStyle ?? inverseTheme.textTheme.subtitle1;
+    final TextStyle? contentTextStyle = snackBarTheme.contentTextStyle ?? ThemeData(brightness: brightness).textTheme.subtitle1;
     final SnackBarBehavior snackBarBehavior = widget.behavior ?? snackBarTheme.behavior ?? SnackBarBehavior.fixed;
     final bool isFloatingSnackBar = snackBarBehavior == SnackBarBehavior.floating;
     final double horizontalPadding = isFloatingSnackBar ? 16.0 : 24.0;
@@ -539,7 +536,7 @@ class _SnackBarState extends State<SnackBar> {
     }
 
     final double elevation = widget.elevation ?? snackBarTheme.elevation ?? 6.0;
-    final Color backgroundColor = widget.backgroundColor ?? snackBarTheme.backgroundColor ?? inverseTheme.backgroundColor;
+    final Color backgroundColor = widget.backgroundColor ?? snackBarTheme.backgroundColor ?? inverseTheme.colorScheme.background;
     final ShapeBorder? shape = widget.shape
       ?? snackBarTheme.shape
       ?? (isFloatingSnackBar ? RoundedRectangleBorder(borderRadius: BorderRadius.circular(4.0)) : null);

packages/flutter/test/material/snack_bar_test.dart

@@ -669,6 +669,152 @@ void main() {
     expect(renderModel.color, equals(darkTheme.colorScheme.onSurface));
   });
 
+  testWidgets('SnackBar should inherit theme data from its ancestor.', (WidgetTester tester) async {
+    final SliderThemeData sliderTheme = SliderThemeData.fromPrimaryColors(
+      primaryColor: Colors.black,
+      primaryColorDark: Colors.black,
+      primaryColorLight: Colors.black,
+      valueIndicatorTextStyle: const TextStyle(color: Colors.black),
+    );
+
+    final ChipThemeData chipTheme = ChipThemeData.fromDefaults(
+      primaryColor: Colors.black,
+      secondaryColor: Colors.white,
+      labelStyle: const TextStyle(color: Colors.black),
+    );
+
+    const PageTransitionsTheme pageTransitionTheme = PageTransitionsTheme(
+      builders: <TargetPlatform, PageTransitionsBuilder>{
+        TargetPlatform.iOS: CupertinoPageTransitionsBuilder(),
+        TargetPlatform.macOS: CupertinoPageTransitionsBuilder(),
+      },
+    );
+
+    final ThemeData theme = ThemeData.raw(
+      visualDensity: const VisualDensity(),
+      primaryColor: Colors.black,
+      primaryColorBrightness: Brightness.dark,
+      primaryColorLight: Colors.black,
+      primaryColorDark: Colors.black,
+      accentColor: Colors.black,
+      accentColorBrightness: Brightness.dark,
+      canvasColor: Colors.black,
+      shadowColor: Colors.black,
+      scaffoldBackgroundColor: Colors.black,
+      bottomAppBarColor: Colors.black,
+      cardColor: Colors.black,
+      dividerColor: Colors.black,
+      focusColor: Colors.black,
+      hoverColor: Colors.black,
+      highlightColor: Colors.black,
+      splashColor: Colors.black,
+      splashFactory: InkRipple.splashFactory,
+      selectedRowColor: Colors.black,
+      unselectedWidgetColor: Colors.black,
+      disabledColor: Colors.black,
+      buttonTheme: const ButtonThemeData(colorScheme: ColorScheme.dark()),
+      toggleButtonsTheme: const ToggleButtonsThemeData(textStyle: TextStyle(color: Colors.black)),
+      buttonColor: Colors.black,
+      secondaryHeaderColor: Colors.black,
+      textSelectionColor: Colors.black,
+      cursorColor: Colors.black,
+      textSelectionHandleColor: Colors.black,
+      backgroundColor: Colors.black,
+      dialogBackgroundColor: Colors.black,
+      indicatorColor: Colors.black,
+      hintColor: Colors.black,
+      errorColor: Colors.black,
+      toggleableActiveColor: Colors.black,
+      textTheme: ThemeData.dark().textTheme,
+      primaryTextTheme: ThemeData.dark().textTheme,
+      accentTextTheme: ThemeData.dark().textTheme,
+      inputDecorationTheme: ThemeData.dark().inputDecorationTheme.copyWith(border: const OutlineInputBorder()),
+      iconTheme: ThemeData.dark().iconTheme,
+      primaryIconTheme: ThemeData.dark().iconTheme,
+      accentIconTheme: ThemeData.dark().iconTheme,
+      sliderTheme: sliderTheme,
+      tabBarTheme: const TabBarTheme(labelColor: Colors.black),
+      tooltipTheme: const TooltipThemeData(height: 100),
+      cardTheme: const CardTheme(color: Colors.black),
+      chipTheme: chipTheme,
+      platform: TargetPlatform.iOS,
+      materialTapTargetSize: MaterialTapTargetSize.shrinkWrap,
+      applyElevationOverlayColor: false,
+      pageTransitionsTheme: pageTransitionTheme,
+      appBarTheme: const AppBarTheme(color: Colors.black),
+      bottomAppBarTheme: const BottomAppBarTheme(color: Colors.black),
+      colorScheme: const ColorScheme.light(),
+      dialogTheme: const DialogTheme(backgroundColor: Colors.black),
+      floatingActionButtonTheme: const FloatingActionButtonThemeData(backgroundColor: Colors.black),
+      navigationRailTheme: const NavigationRailThemeData(backgroundColor: Colors.black),
+      typography: Typography.material2018(platform: TargetPlatform.android),
+      cupertinoOverrideTheme: null,
+      snackBarTheme: const SnackBarThemeData(backgroundColor: Colors.black),
+      bottomSheetTheme: const BottomSheetThemeData(backgroundColor: Colors.black),
+      popupMenuTheme: const PopupMenuThemeData(color: Colors.black),
+      bannerTheme: const MaterialBannerThemeData(backgroundColor: Colors.black),
+      dividerTheme: const DividerThemeData(color: Colors.black),
+      buttonBarTheme: const ButtonBarThemeData(alignment: MainAxisAlignment.start),
+      bottomNavigationBarTheme: const BottomNavigationBarThemeData(type: BottomNavigationBarType.fixed),
+      timePickerTheme: const TimePickerThemeData(backgroundColor: Colors.black),
+      textButtonTheme: TextButtonThemeData(style: TextButton.styleFrom(primary: Colors.red)),
+      elevatedButtonTheme: ElevatedButtonThemeData(style: ElevatedButton.styleFrom(primary: Colors.green)),
+      outlinedButtonTheme: OutlinedButtonThemeData(style: OutlinedButton.styleFrom(primary: Colors.blue)),
+      textSelectionTheme: const TextSelectionThemeData(cursorColor: Colors.black),
+      dataTableTheme: const DataTableThemeData(),
+      checkboxTheme: const CheckboxThemeData(),
+      radioTheme: const RadioThemeData(),
+      switchTheme: const SwitchThemeData(),
+      fixTextFieldOutlineLabel: false,
+      useTextSelectionTheme: false,
+    );
+
+    ThemeData? themeBeforeSnackBar;
+    ThemeData? themeAfterSnackBar;
+    await tester.pumpWidget(
+      MaterialApp(
+        theme: theme,
+        home: Scaffold(
+          body: Builder(
+            builder: (BuildContext context) {
+              themeBeforeSnackBar = Theme.of(context);
+              return GestureDetector(
+                onTap: () {
+                  Scaffold.of(context).showSnackBar(
+                    SnackBar(
+                      content: Builder(
+                        builder: (BuildContext context) {
+                          themeAfterSnackBar = Theme.of(context);
+                          return const Text('I am a snack bar.');
+                        },
+                      ),
+                      duration: const Duration(seconds: 2),
+                      action: SnackBarAction(
+                        label: 'ACTION',
+                        onPressed: () { },
+                      ),
+                    ),
+                  );
+                },
+                child: const Text('X'),
+              );
+            },
+          ),
+        ),
+      ),
+    );
+
+    await tester.tap(find.text('X'));
+    await tester.pump(); // start animation
+    await tester.pump(const Duration(milliseconds: 750));
+
+    final ThemeData comparedTheme = themeBeforeSnackBar!.copyWith(
+      colorScheme: themeAfterSnackBar!.colorScheme,
+    ); // Fields replaced by SnackBar.
+
+    expect(comparedTheme, themeAfterSnackBar);
+  });
+
   testWidgets('Snackbar margin can be customized', (WidgetTester tester) async {
     const double padding = 20.0;
     await tester.pumpWidget(

packages/flutter/test/material/text_selection_theme_test.dart

@@ -93,7 +93,7 @@ void main() {
     expect(handle, paints..path(color: defaultSelectionHandleColor));
   });
 
-  testWidgets('ThemeDate.textSelectionTheme will be used if provided', (WidgetTester tester) async {
+  testWidgets('ThemeData.textSelectionTheme will be used if provided', (WidgetTester tester) async {
     const TextSelectionThemeData textSelectionTheme = TextSelectionThemeData(
       cursorColor: Color(0xffaabbcc),
       selectionColor: Color(0x88888888),
@@ -138,7 +138,7 @@ void main() {
     expect(handle, paints..path(color: textSelectionTheme.selectionHandleColor));
   });
 
-  testWidgets('TextSelectionTheme widget will override ThemeDate.textSelectionTheme', (WidgetTester tester) async {
+  testWidgets('TextSelectionTheme widget will override ThemeData.textSelectionTheme', (WidgetTester tester) async {
     const TextSelectionThemeData defaultTextSelectionTheme = TextSelectionThemeData(
       cursorColor: Color(0xffaabbcc),
       selectionColor: Color(0x88888888),