[EditableText] honor the "brieflyShowPassword" system setting (#97769)

packages/flutter/lib/src/widgets/editable_text.dart

@@ -1923,13 +1923,13 @@ class EditableTextState extends State<EditableText> with AutomaticKeepAliveClien
       hideToolbar();
       _currentPromptRectRange = null;
 
-      if (_hasInputConnection) {
-        if (widget.obscureText && value.text.length == _value.text.length + 1) {
-          _obscureShowCharTicksPending = _kObscureShowLatestCharCursorTicks;
-          _obscureLatestCharIndex = _value.selection.baseOffset;
-        }
-      }
+      final bool revealObscuredInput = _hasInputConnection
+                                    && widget.obscureText
+                                    && WidgetsBinding.instance!.window.brieflyShowPassword
+                                    && value.text.length == _value.text.length + 1;
 
+      _obscureShowCharTicksPending = revealObscuredInput ? _kObscureShowLatestCharCursorTicks : 0;
+      _obscureLatestCharIndex = revealObscuredInput ? _value.selection.baseOffset : null;
       _formatAndSetValue(value, SelectionChangedCause.keyboard);
     }
 
@@ -2621,7 +2621,9 @@ class EditableTextState extends State<EditableText> with AutomaticKeepAliveClien
 
     if (_obscureShowCharTicksPending > 0) {
       setState(() {
-        _obscureShowCharTicksPending--;
+        _obscureShowCharTicksPending = WidgetsBinding.instance!.window.brieflyShowPassword
+          ? _obscureShowCharTicksPending - 1
+          : 0;
       });
     }
   }
@@ -3245,11 +3247,13 @@ class EditableTextState extends State<EditableText> with AutomaticKeepAliveClien
       String text = _value.text;
       text = widget.obscuringCharacter * text.length;
       // Reveal the latest character in an obscured field only on mobile.
-      if (defaultTargetPlatform == TargetPlatform.android ||
-          defaultTargetPlatform == TargetPlatform.iOS ||
-          defaultTargetPlatform == TargetPlatform.fuchsia) {
-        final int? o =
-            _obscureShowCharTicksPending > 0 ? _obscureLatestCharIndex : null;
+      const Set<TargetPlatform> mobilePlatforms = <TargetPlatform> {
+        TargetPlatform.android, TargetPlatform.iOS, TargetPlatform.fuchsia,
+      };
+      final bool breiflyShowPassword = WidgetsBinding.instance!.window.brieflyShowPassword
+                                    && mobilePlatforms.contains(defaultTargetPlatform);
+      if (breiflyShowPassword) {
+        final int? o = _obscureShowCharTicksPending > 0 ? _obscureLatestCharIndex : null;
         if (o != null && o >= 0 && o < text.length)
           text = text.replaceRange(o, o + 1, _value.text.substring(o, o + 1));
       }

packages/flutter/test/widgets/editable_text_test.dart

@@ -3611,6 +3611,72 @@ void main() {
     expect((findRenderEditable(tester).text! as TextSpan).text, expectedValue);
   });
 
+  testWidgets('password briefly shows last character when entered on mobile', (WidgetTester tester) async {
+    final bool debugDeterministicCursor = EditableText.debugDeterministicCursor;
+    EditableText.debugDeterministicCursor = false;
+    addTearDown(() {
+      EditableText.debugDeterministicCursor = debugDeterministicCursor;
+    });
+
+    await tester.pumpWidget(MaterialApp(
+      home: EditableText(
+        backgroundCursorColor: Colors.grey,
+        controller: controller,
+        obscureText: true,
+        focusNode: focusNode,
+        style: textStyle,
+        cursorColor: cursorColor,
+      ),
+    ));
+
+    await tester.enterText(find.byType(EditableText), 'AA');
+    await tester.pump();
+    await tester.enterText(find.byType(EditableText), 'AAA');
+    await tester.pump();
+
+    expect((findRenderEditable(tester).text! as TextSpan).text, '••A');
+    await tester.pump(const Duration(milliseconds: 500));
+    await tester.pump(const Duration(milliseconds: 500));
+    await tester.pump(const Duration(milliseconds: 500));
+    expect((findRenderEditable(tester).text! as TextSpan).text, '•••');
+  });
+
+  testWidgets('password briefly does not show last character on Android if turned off', (WidgetTester tester) async {
+    final bool debugDeterministicCursor = EditableText.debugDeterministicCursor;
+    EditableText.debugDeterministicCursor = false;
+    addTearDown(() {
+      EditableText.debugDeterministicCursor = debugDeterministicCursor;
+    });
+
+    await tester.pumpWidget(MaterialApp(
+      home: EditableText(
+        backgroundCursorColor: Colors.grey,
+        controller: controller,
+        obscureText: true,
+        focusNode: focusNode,
+        style: textStyle,
+        cursorColor: cursorColor,
+      ),
+    ));
+
+    await tester.enterText(find.byType(EditableText), 'AA');
+    await tester.pump();
+    await tester.enterText(find.byType(EditableText), 'AAA');
+    await tester.pump();
+
+    tester.binding.window.brieflyShowPasswordTestValue = false;
+    addTearDown(() {
+      tester.binding.window.brieflyShowPasswordTestValue = true;
+    });
+    expect((findRenderEditable(tester).text! as TextSpan).text, '••A');
+    await tester.pump(const Duration(milliseconds: 500));
+    expect((findRenderEditable(tester).text! as TextSpan).text, '•••');
+    await tester.pump(const Duration(milliseconds: 500));
+    await tester.pump(const Duration(milliseconds: 500));
+    await tester.pump(const Duration(milliseconds: 500));
+    expect((findRenderEditable(tester).text! as TextSpan).text, '•••');
+  });
+
   group('a11y copy/cut/paste', () {
     Future<void> _buildApp(MockTextSelectionControls controls, WidgetTester tester) {
       return tester.pumpWidget(MaterialApp(

packages/flutter_test/lib/src/window.dart

@@ -271,6 +271,15 @@ class TestWindow implements ui.SingletonFlutterWindow {
     platformDispatcher.onTextScaleFactorChanged = callback;
   }
 
+  @override
+  bool get brieflyShowPassword => _brieflyShowPasswordTestValue ?? platformDispatcher.brieflyShowPassword;
+  bool? _brieflyShowPasswordTestValue;
+  /// Hides the real [brieflyShowPassword] and reports the given
+  /// `brieflyShowPasswordTestValue` instead.
+  set brieflyShowPasswordTestValue(bool brieflyShowPasswordTestValue) { // ignore: avoid_setters_without_getters
+    _brieflyShowPasswordTestValue = brieflyShowPasswordTestValue;
+  }
+
   @override
   ui.FrameCallback? get onBeginFrame => platformDispatcher.onBeginFrame;
   @override

packages/flutter_test/test/window_test.dart

@@ -127,6 +127,18 @@ void main() {
     );
   });
 
+  testWidgets('TestWindow can fake brieflyShowPassword', (WidgetTester tester) async {
+    verifyThatTestWindowCanFakeProperty<bool>(
+      tester: tester,
+      realValue: ui.window.brieflyShowPassword,
+      fakeValue: !ui.window.brieflyShowPassword,
+      propertyRetriever: () => WidgetsBinding.instance!.window.brieflyShowPassword,
+      propertyFaker: (TestWidgetsFlutterBinding binding, bool fakeValue) {
+        binding.window.brieflyShowPasswordTestValue = fakeValue;
+      },
+    );
+  });
+
   testWidgets('TestWindow can fake default route name', (WidgetTester tester) async {
     verifyThatTestWindowCanFakeProperty<String>(
       tester: tester,