Add clip option for navigator (#115775)

Author: chunhtai

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

@@ -1385,7 +1385,7 @@ class Navigator extends StatefulWidget {
   /// Creates a widget that maintains a stack-based history of child widgets.
   ///
   /// The [onGenerateRoute], [pages], [onGenerateInitialRoutes],
-  /// [transitionDelegate], [observers]  arguments must not be null.
+  /// [transitionDelegate], [observers] arguments must not be null.
   ///
   /// If the [pages] is not empty, the [onPopPage] must not be null.
   const Navigator({
@@ -1398,6 +1398,7 @@ class Navigator extends StatefulWidget {
     this.onUnknownRoute,
     this.transitionDelegate = const DefaultTransitionDelegate<dynamic>(),
     this.reportsRouteUpdateToEngine = false,
+    this.clipBehavior = Clip.hardEdge,
     this.observers = const <NavigatorObserver>[],
     this.requestFocus = true,
     this.restorationScopeId,
@@ -1563,6 +1564,14 @@ class Navigator extends StatefulWidget {
   /// Defaults to false.
   final bool reportsRouteUpdateToEngine;
 
+  /// {@macro flutter.material.Material.clipBehavior}
+  ///
+  /// In cases where clipping is not desired, consider setting this property to
+  /// [Clip.none].
+  ///
+  /// Defaults to [Clip.hardEdge], and must not be null.
+  final Clip clipBehavior;
+
   /// Whether or not the navigator and it's new topmost route should request focus
   /// when the new route is pushed onto the navigator.
   ///
@@ -5253,6 +5262,7 @@ class NavigatorState extends State<Navigator> with TickerProviderStateMixin, Res
                 bucket: bucket,
                 child: Overlay(
                   key: _overlayKey,
+                  clipBehavior: widget.clipBehavior,
                   initialEntries: overlay == null ?  _allRouteOverlayEntries.toList(growable: false) : const <OverlayEntry>[],
                 ),
               ),

packages/flutter/test/widgets/navigator_test.dart

@@ -200,6 +200,39 @@ void main() {
     expect(find.text('home'), findsOneWidget);
   });
 
+  testWidgets('Navigator can set clip behavior', (WidgetTester tester) async {
+    const MaterialPage<void> page = MaterialPage<void>(child: Text('page'));
+    await tester.pumpWidget(
+      MediaQuery(
+        data: MediaQueryData.fromWindow(WidgetsBinding.instance.window),
+        child: Directionality(
+          textDirection: TextDirection.ltr,
+          child: Navigator(
+            pages: const <Page<void>>[page],
+            onPopPage: (_, __) => false,
+          ),
+        ),
+      ),
+    );
+    // Default to hard edge.
+    expect(tester.widget<Overlay>(find.byType(Overlay)).clipBehavior, Clip.hardEdge);
+
+    await tester.pumpWidget(
+      MediaQuery(
+        data: MediaQueryData.fromWindow(WidgetsBinding.instance.window),
+        child: Directionality(
+          textDirection: TextDirection.ltr,
+          child: Navigator(
+            pages: const <Page<void>>[page],
+            clipBehavior: Clip.none,
+            onPopPage: (_, __) => false,
+          ),
+        ),
+      ),
+    );
+    expect(tester.widget<Overlay>(find.byType(Overlay)).clipBehavior, Clip.none);
+  });
+
   testWidgets('Zero transition page-based route correctly notifies observers when it is popped', (WidgetTester tester) async {
     final List<Page<void>> pages = <Page<void>>[
       const ZeroTransitionPage(name: 'Page 1'),