Fix text scale factor for non-content components of Cupertino scaffolds (#38593)

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

@@ -31,6 +31,14 @@ const Color _kDefaultTabBarBorderColor = Color(0x4C000000);
 /// If the given [backgroundColor]'s opacity is not 1.0 (which is the case by
 /// default), it will produce a blurring effect to the content behind it.
 ///
+/// When used as [CupertinoTabScaffold.tabBar], by default `CupertinoTabBar` has
+/// its text scale factor set to 1.0 and does not respond to text scale factor
+/// changes from the operating system, to match the native iOS behavior. To override
+/// this behavior, wrap each of the `navigationBar`'s components inside a [MediaQuery]
+/// with the desired [MediaQueryData.textScaleFactor] value. The text scale factor
+/// value from the operating system can be retrieved in many ways, such as querying
+/// [MediaQuery.textScaleFactorOf] against [CupertinoApp]'s [BuildContext].
+///
 /// See also:
 ///
 ///  * [CupertinoTabScaffold], which hosts the [CupertinoTabBar] at the bottom.

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

@@ -179,6 +179,14 @@ bool _isTransitionable(BuildContext context) {
 /// Use [transitionBetweenRoutes] or [heroTag] to customize the transition
 /// behavior for multiple navigation bars per route.
 ///
+/// When used in a [CupertinoPageScaffold], [CupertinoPageScaffold.navigationBar]
+/// has its text scale factor set to 1.0 and does not respond to text scale factor
+/// changes from the operating system, to match the native iOS behavior. To override
+/// this behavior, wrap each of the `navigationBar`'s components inside a [MediaQuery]
+/// with the desired [MediaQueryData.textScaleFactor] value. The text scale factor
+/// value from the operating system can be retrieved in many ways, such as querying
+/// [MediaQuery.textScaleFactorOf] against [CupertinoApp]'s [BuildContext].
+///
 /// See also:
 ///
 ///  * [CupertinoPageScaffold], a page layout helper typically hosting the
@@ -499,6 +507,14 @@ class _CupertinoNavigationBarState extends State<CupertinoNavigationBar> {
 /// Use [transitionBetweenRoutes] or [heroTag] to customize the transition
 /// behavior for multiple navigation bars per route.
 ///
+/// `CupertinoSliverNavigationBar` has its text scale factor set to 1.0 by default
+/// and does not respond to text scale factor changes from the operating system,
+/// to match the native iOS behavior. To override this behavior, wrap each of the
+/// `CupertinoSliverNavigationBar`'s components inside a [MediaQuery] with the
+/// desired [MediaQueryData.textScaleFactor] value. The text scale factor value
+/// from the operating system can be retrieved in many ways, such as querying
+/// [MediaQuery.textScaleFactorOf] against [CupertinoApp]'s [BuildContext].
+///
 /// See also:
 ///
 ///  * [CupertinoNavigationBar], an iOS navigation bar for use on non-scrolling
@@ -652,20 +668,23 @@ class _CupertinoSliverNavigationBarState extends State<CupertinoSliverNavigation
       // Lint ignore to maintain backward compatibility.
       widget.actionsForegroundColor, // ignore: deprecated_member_use_from_same_package
       context,
-      SliverPersistentHeader(
-        pinned: true, // iOS navigation bars are always pinned.
-        delegate: _LargeTitleNavigationBarSliverDelegate(
-          keys: keys,
-          components: components,
-          userMiddle: widget.middle,
-          backgroundColor: widget.backgroundColor ?? CupertinoTheme.of(context).barBackgroundColor,
-          border: widget.border,
-          padding: widget.padding,
-          actionsForegroundColor: actionsForegroundColor,
-          transitionBetweenRoutes: widget.transitionBetweenRoutes,
-          heroTag: widget.heroTag,
-          persistentHeight: _kNavBarPersistentHeight + MediaQuery.of(context).padding.top,
-          alwaysShowMiddle: widget.middle != null,
+      MediaQuery(
+        data: MediaQuery.of(context).copyWith(textScaleFactor: 1),
+        child: SliverPersistentHeader(
+          pinned: true, // iOS navigation bars are always pinned.
+          delegate: _LargeTitleNavigationBarSliverDelegate(
+            keys: keys,
+            components: components,
+            userMiddle: widget.middle,
+            backgroundColor: widget.backgroundColor ?? CupertinoTheme.of(context).barBackgroundColor,
+            border: widget.border,
+            padding: widget.padding,
+            actionsForegroundColor: actionsForegroundColor,
+            transitionBetweenRoutes: widget.transitionBetweenRoutes,
+            heroTag: widget.heroTag,
+            persistentHeight: _kNavBarPersistentHeight + MediaQuery.of(context).padding.top,
+            alwaysShowMiddle: widget.middle != null,
+          ),
         ),
       ),
     );

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

@@ -34,8 +34,16 @@ class CupertinoPageScaffold extends StatefulWidget {
   /// If translucent, the main content may slide behind it.
   /// Otherwise, the main content's top margin will be offset by its height.
   ///
-  /// The scaffold assumes the navigation bar will account for the [MediaQuery] top padding,
-  /// also consume it if the navigation bar is opaque.
+  /// The scaffold assumes the navigation bar will account for the [MediaQuery]
+  /// top padding, also consume it if the navigation bar is opaque.
+  ///
+  /// By default `navigationBar` has its text scale factor set to 1.0 and does
+  /// not respond to text scale factor changes from the operating system, to match
+  /// the native iOS behavior. To override such behavior, wrap each of the `navigationBar`'s
+  /// components inside a [MediaQuery] with the desired [MediaQueryData.textScaleFactor]
+  /// value. The text scale factor value from the operating system can be retrieved
+  /// in many ways, such as querying [MediaQuery.textScaleFactorOf] against
+  /// [CupertinoApp]'s [BuildContext].
   // TODO(xster): document its page transition animation when ready
   final ObstructingPreferredSizeWidget navigationBar;
 
@@ -160,7 +168,10 @@ class _CupertinoPageScaffoldState extends State<CupertinoPageScaffold> {
         top: 0.0,
         left: 0.0,
         right: 0.0,
-        child: widget.navigationBar,
+        child: MediaQuery(
+          data: existingMediaQuery.copyWith(textScaleFactor: 1),
+          child: widget.navigationBar,
+        ),
       ));
     }
 

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

@@ -237,6 +237,14 @@ class CupertinoTabScaffold extends StatefulWidget {
   /// If translucent, the main content may slide behind it.
   /// Otherwise, the main content's bottom margin will be offset by its height.
   ///
+  /// By default `tabBar` has its text scale factor set to 1.0 and does not
+  /// respond to text scale factor changes from the operating system, to match
+  /// the native iOS behavior. To override this behavior, wrap each of the `tabBar`'s
+  /// items inside a [MediaQuery] with the desired [MediaQueryData.textScaleFactor]
+  /// value. The text scale factor value from the operating system can be retrieved
+  /// int many ways, such as querying [MediaQuery.textScaleFactorOf] against
+  /// [CupertinoApp]'s [BuildContext].
+  ///
   /// Must not be null.
   final CupertinoTabBar tabBar;
 
@@ -392,23 +400,26 @@ class _CupertinoTabScaffoldState extends State<CupertinoTabScaffold> {
     // The main content being at the bottom is added to the stack first.
     stacked.add(content);
 
-    if (widget.tabBar != null) {
-      stacked.add(Align(
-        alignment: Alignment.bottomCenter,
-        // Override the tab bar's currentIndex to the current tab and hook in
-        // our own listener to update the [_controller.currentIndex] on top of a possibly user
-        // provided callback.
-        child: widget.tabBar.copyWith(
-          currentIndex: _controller.index,
-          onTap: (int newIndex) {
-            _controller.index = newIndex;
-            // Chain the user's original callback.
-            if (widget.tabBar.onTap != null)
+    stacked.add(
+      MediaQuery(
+        data: existingMediaQuery.copyWith(textScaleFactor: 1),
+        child: Align(
+          alignment: Alignment.bottomCenter,
+          // Override the tab bar's currentIndex to the current tab and hook in
+          // our own listener to update the [_controller.currentIndex] on top of a possibly user
+          // provided callback.
+          child: widget.tabBar.copyWith(
+            currentIndex: _controller.index,
+            onTap: (int newIndex) {
+              _controller.index = newIndex;
+              // Chain the user's original callback.
+              if (widget.tabBar.onTap != null)
               widget.tabBar.onTap(newIndex);
-          },
+            },
+          ),
         ),
-      ));
-    }
+      ),
+    );
 
     return DecoratedBox(
       decoration: BoxDecoration(

packages/flutter/test/cupertino/material/tab_scaffold_test.dart

@@ -221,6 +221,48 @@ void main() {
     expect(tester.state<EditableTextState>(find.byType(EditableText)), editableState);
     expect(find.text("don't lose me"), findsOneWidget);
   });
+
+  testWidgets('textScaleFactor is set to 1.0', (WidgetTester tester) async {
+    await tester.pumpWidget(
+      MaterialApp(
+        home: Builder(builder: (BuildContext context) {
+          return MediaQuery(
+            data: MediaQuery.of(context).copyWith(textScaleFactor: 99),
+            child: CupertinoTabScaffold(
+              tabBar: CupertinoTabBar(
+                items: List<BottomNavigationBarItem>.generate(
+                  10,
+                  (int i) => BottomNavigationBarItem(icon: const ImageIcon(TestImageProvider(24, 23)), title: Text('$i'))
+                ),
+              ),
+              tabBuilder: (BuildContext context, int index) => const Text('content'),
+            ),
+          );
+        }),
+      ),
+    );
+
+    final Iterable<RichText> barItems = tester.widgetList<RichText>(
+      find.descendant(
+        of: find.byType(CupertinoTabBar),
+        matching: find.byType(RichText),
+      ),
+    );
+
+    final Iterable<RichText> contents = tester.widgetList<RichText>(
+      find.descendant(
+        of: find.text('content'),
+        matching: find.byType(RichText),
+        skipOffstage: false,
+      ),
+    );
+
+    expect(barItems.length, greaterThan(0));
+    expect(barItems.any((RichText t) => t.textScaleFactor != 1), isFalse);
+
+    expect(contents.length, greaterThan(0));
+    expect(contents.any((RichText t) => t.textScaleFactor != 99), isFalse);
+  });
 }
 
 CupertinoTabBar _buildTabBar({ int selectedTab = 0 }) {

packages/flutter/test/cupertino/nav_bar_test.dart

@@ -1018,6 +1018,91 @@ void main() {
       expect(backPressed, true);
     }
   );
+
+  testWidgets('textScaleFactor is set to 1.0', (WidgetTester tester) async {
+    await tester.pumpWidget(
+      CupertinoApp(
+        home: Builder(builder: (BuildContext context) {
+          return MediaQuery(
+            data: MediaQuery.of(context).copyWith(textScaleFactor: 99),
+            child: CupertinoPageScaffold(
+              child: CustomScrollView(
+                slivers: <Widget>[
+                  const CupertinoSliverNavigationBar(
+                    leading: Text('leading'),
+                    middle: Text('middle'),
+                    largeTitle: Text('Large Title'),
+                    trailing: Text('trailing'),
+                  ),
+                  SliverToBoxAdapter(
+                    child: Container(
+                      child: const Text('content'),
+                    ),
+                  ),
+                ],
+              ),
+            ),
+          );
+        }),
+      ),
+    );
+
+    final Iterable<RichText> barItems = tester.widgetList<RichText>(
+      find.descendant(
+        of: find.byType(CupertinoSliverNavigationBar),
+        matching: find.byType(RichText),
+      ),
+    );
+
+    final Iterable<RichText> contents = tester.widgetList<RichText>(
+      find.descendant(
+        of: find.text('content'),
+        matching: find.byType(RichText),
+      ),
+    );
+
+    expect(barItems.length, greaterThan(0));
+    expect(barItems.any((RichText t) => t.textScaleFactor != 1), isFalse);
+
+    expect(contents.length, greaterThan(0));
+    expect(contents.any((RichText t) => t.textScaleFactor != 99), isFalse);
+
+    // Also works with implicitly added widgets.
+    tester.state<NavigatorState>(find.byType(Navigator)).push(CupertinoPageRoute<void>(
+      title: 'title',
+      builder: (BuildContext context) {
+        return MediaQuery(
+          data: MediaQuery.of(context).copyWith(textScaleFactor: 99),
+          child: Container(
+            child: const CupertinoPageScaffold(
+              child: CustomScrollView(
+                slivers: <Widget>[
+                  CupertinoSliverNavigationBar(
+                    automaticallyImplyLeading: true,
+                    automaticallyImplyTitle: true,
+                    previousPageTitle: 'previous title',
+                  ),
+                ],
+              ),
+            ),
+          ),
+        );
+      },
+    ));
+
+    await tester.pump();
+    await tester.pump(const Duration(milliseconds: 500));
+
+    final Iterable<RichText> barItems2 = tester.widgetList<RichText>(
+      find.descendant(
+        of: find.byType(CupertinoSliverNavigationBar),
+        matching: find.byType(RichText),
+      ),
+    );
+
+    expect(barItems2.length, greaterThan(0));
+    expect(barItems2.any((RichText t) => t.textScaleFactor != 1), isFalse);
+  });
 }
 
 class _ExpectStyles extends StatelessWidget {

packages/flutter/test/cupertino/scaffold_test.dart

@@ -481,4 +481,32 @@ void main() {
     expect(positionWithInsetNoNavBar.dy, lessThan(positionNoInsetNoNavBar.dy));
     expect(positionWithInsetNoNavBar, equals(positionWithInsetWithNavBar));
   });
+
+  testWidgets('textScaleFactor is set to 1.0', (WidgetTester tester) async {
+    await tester.pumpWidget(
+      CupertinoApp(
+        home: Builder(builder: (BuildContext context) {
+          return MediaQuery(
+            data: MediaQuery.of(context).copyWith(textScaleFactor: 99),
+            child: const CupertinoPageScaffold(
+              navigationBar: CupertinoNavigationBar(
+                middle: Text('middle'),
+                leading: Text('leading'),
+                trailing: Text('trailing'),
+              ),
+              child: Text('content'),
+            ),
+          );
+        }),
+      ),
+    );
+    final Iterable<RichText> richTextList = tester.widgetList<RichText>(
+      find.descendant(of: find.byType(CupertinoNavigationBar), matching: find.byType(RichText)),
+    );
+
+    expect(richTextList.length, greaterThan(0));
+    expect(richTextList.any((RichText text) => text.textScaleFactor != 1), isFalse);
+
+    expect(tester.widget<RichText>(find.descendant(of: find.text('content'), matching: find.byType(RichText))).textScaleFactor, 99);
+  });
 }

packages/flutter/test/cupertino/tab_scaffold_test.dart

@@ -981,6 +981,48 @@ void main() {
     expect(tester.state<EditableTextState>(find.byType(EditableText)), editableState);
     expect(find.text("don't lose me"), findsOneWidget);
   });
+
+  testWidgets('textScaleFactor is set to 1.0', (WidgetTester tester) async {
+    await tester.pumpWidget(
+      CupertinoApp(
+        home: Builder(builder: (BuildContext context) {
+          return MediaQuery(
+            data: MediaQuery.of(context).copyWith(textScaleFactor: 99),
+            child: CupertinoTabScaffold(
+              tabBar: CupertinoTabBar(
+                items: List<BottomNavigationBarItem>.generate(
+                  10,
+                  (int i) => BottomNavigationBarItem(icon: const ImageIcon(TestImageProvider(24, 23)), title: Text('$i'))
+                ),
+              ),
+              tabBuilder: (BuildContext context, int index) => const Text('content'),
+            ),
+          );
+        }),
+      ),
+    );
+
+    final Iterable<RichText> barItems = tester.widgetList<RichText>(
+      find.descendant(
+        of: find.byType(CupertinoTabBar),
+        matching: find.byType(RichText),
+      ),
+    );
+
+    final Iterable<RichText> contents = tester.widgetList<RichText>(
+      find.descendant(
+        of: find.text('content'),
+        matching: find.byType(RichText),
+        skipOffstage: false,
+      ),
+    );
+
+    expect(barItems.length, greaterThan(0));
+    expect(barItems.any((RichText t) => t.textScaleFactor != 1), isFalse);
+
+    expect(contents.length, greaterThan(0));
+    expect(contents.any((RichText t) => t.textScaleFactor != 99), isFalse);
+  });
 }
 
 CupertinoTabBar _buildTabBar({ int selectedTab = 0 }) {