Dismiss Modal Barrier on `handleTapCancel` (#98191)

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

@@ -47,7 +47,8 @@ class ModalBarrier extends StatelessWidget {
   ///    [ModalBarrier] built by [ModalRoute] pages.
   final Color? color;
 
-  /// Specifies if the barrier will be dismissed when the user taps on it.
+  /// Specifies if the barrier will be dismissed when the user taps or
+  /// performs a scroll gesture on it.
   ///
   /// If true, and [onDismiss] is non-null, [onDismiss] will be called,
   /// otherwise the current route will be popped from the ambient [Navigator].
@@ -228,12 +229,14 @@ class _AnyTapGestureRecognizer extends BaseTapGestureRecognizer {
     : super(debugOwner: debugOwner);
 
   VoidCallback? onAnyTapUp;
+  VoidCallback? onAnyTapCancel;
 
   @protected
   @override
   bool isPointerAllowed(PointerDownEvent event) {
-    if (onAnyTapUp == null)
+    if (onAnyTapUp == null && onAnyTapCancel == null) {
       return false;
+    }
     return super.isPointerAllowed(event);
   }
 
@@ -252,7 +255,7 @@ class _AnyTapGestureRecognizer extends BaseTapGestureRecognizer {
   @protected
   @override
   void handleTapCancel({PointerDownEvent? down, PointerCancelEvent? cancel, String? reason}) {
-    // Do nothing.
+    onAnyTapCancel?.call();
   }
 
   @override
@@ -272,9 +275,10 @@ class _ModalBarrierSemanticsDelegate extends SemanticsGestureDelegate {
 
 
 class _AnyTapGestureRecognizerFactory extends GestureRecognizerFactory<_AnyTapGestureRecognizer> {
-  const _AnyTapGestureRecognizerFactory({this.onAnyTapUp});
+  const _AnyTapGestureRecognizerFactory({this.onAnyTapUp, this.onAnyTapCancel});
 
   final VoidCallback? onAnyTapUp;
+  final VoidCallback? onAnyTapCancel;
 
   @override
   _AnyTapGestureRecognizer constructor() => _AnyTapGestureRecognizer();
@@ -282,6 +286,7 @@ class _AnyTapGestureRecognizerFactory extends GestureRecognizerFactory<_AnyTapGe
   @override
   void initializer(_AnyTapGestureRecognizer instance) {
     instance.onAnyTapUp = onAnyTapUp;
+    instance.onAnyTapCancel = onAnyTapCancel;
   }
 }
 
@@ -307,7 +312,7 @@ class _ModalBarrierGestureDetector extends StatelessWidget {
   @override
   Widget build(BuildContext context) {
     final Map<Type, GestureRecognizerFactory> gestures = <Type, GestureRecognizerFactory>{
-      _AnyTapGestureRecognizer: _AnyTapGestureRecognizerFactory(onAnyTapUp: onDismiss),
+      _AnyTapGestureRecognizer: _AnyTapGestureRecognizerFactory(onAnyTapUp: onDismiss, onAnyTapCancel: onDismiss),
     };
 
     return RawGestureDetector(

packages/flutter/test/widgets/modal_barrier_test.dart

@@ -251,6 +251,39 @@ void main() {
     );
   });
 
+  testWidgets('ModalBarrier pops the Navigator when dismissed by tap cancel', (WidgetTester tester) async {
+    final Map<String, WidgetBuilder> routes = <String, WidgetBuilder>{
+      '/': (BuildContext context) => const FirstWidget(),
+      '/modal': (BuildContext context) => const SecondWidget(),
+    };
+
+    await tester.pumpWidget(MaterialApp(routes: routes));
+
+    // Initially the barrier is not visible
+    expect(find.byKey(const ValueKey<String>('barrier')), findsNothing);
+
+    // Tapping on X routes to the barrier
+    await tester.tap(find.text('X'));
+    await tester.pump(); // begin transition
+    await tester.pump(const Duration(seconds: 1)); // end transition
+
+    // Press the barrier; it shouldn't dismiss yet
+    final TestGesture gesture = await tester.press(
+      find.byKey(const ValueKey<String>('barrier')),
+    );
+    await tester.pumpAndSettle(); // begin transition
+    expect(find.byKey(const ValueKey<String>('barrier')), findsOneWidget);
+
+    // Cancel the pointer; the barrier should be dismissed
+    await gesture.cancel();
+    await tester.pumpAndSettle(const Duration(seconds: 1)); // end transition
+    expect(
+      find.byKey(const ValueKey<String>('barrier')),
+      findsNothing,
+      reason: 'The route should have been dismissed by tapping the barrier.',
+    );
+  });
+
   testWidgets('ModalBarrier may pop the Navigator when competing with other gestures', (WidgetTester tester) async {
     final Map<String, WidgetBuilder> routes = <String, WidgetBuilder>{
       '/': (BuildContext context) => const FirstWidget(),