Fix license page rtl (#120497)

* fix license page rtl

* fix editor spacings, tests to lateral view

* fix defaultSize and setSurfaceSize

* add validation for packageList position

* fix spacing

* simplify align

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

@@ -1400,7 +1400,10 @@ class _MasterDetailScaffoldState extends State<_MasterDetailScaffold>
               ),
             ),
           ),
-          body: _masterPanel(context),
+          body: Align(
+            alignment: AlignmentDirectional.centerStart,
+            child: _masterPanel(context),
+          ),
         ),
         // Detail view stacked above main scaffold and master view.
         SafeArea(

packages/flutter/test/material/about_test.dart

@@ -1067,6 +1067,136 @@ void main() {
     expect(tester.takeException().toString(), 'Exception: Injected failure');
     expect(find.text('Exception: Injected failure'), findsOneWidget);
   });
+
+  testWidgets('LicensePage master view layout position - ltr', (WidgetTester tester) async {
+    const TextDirection textDirection = TextDirection.ltr;
+    const Size defaultSize = Size(800.0, 600.0);
+    const Size wideSize = Size(1200.0, 600.0);
+    const String title = 'License ABC';
+    LicenseRegistry.addLicense(() {
+      return Stream<LicenseEntry>.fromIterable(<LicenseEntry>[
+        const LicenseEntryWithLineBreaks(<String>['ABC'], 'DEF'),
+      ]);
+    });
+
+    // Configure to show the default layout.
+    await tester.binding.setSurfaceSize(defaultSize);
+
+    await tester.pumpWidget(
+      const MaterialApp(
+        title: title,
+        home: Scaffold(
+          body: Directionality(
+            textDirection: textDirection,
+            child: LicensePage(),
+          ),
+        ),
+      ),
+    );
+
+    // To stop loading
+    await tester.pumpAndSettle();
+
+    // If the layout width is less than 840.0 pixels, nested layout is
+    // used which positions license page title at the top center.
+    Offset titleOffset = tester.getCenter(find.text(title));
+    expect(titleOffset, Offset(defaultSize.width / 2, 92.0));
+    expect(tester.getCenter(find.byType(ListView)), Offset(defaultSize.width / 2, 328.0));
+
+    // Configure a wide window to show the lateral UI.
+    await tester.binding.setSurfaceSize(wideSize);
+
+    await tester.pumpWidget(
+      const MaterialApp(
+        title: title,
+        home: Scaffold(
+          body: Directionality(
+            textDirection: textDirection,
+            child: LicensePage(),
+          ),
+        ),
+      ),
+    );
+
+    // To finish the FakeTimer
+    await tester.pumpAndSettle();
+
+    // If the layout width is greater than 840.0 pixels, lateral UI layout
+    // is used which positions license page title and packageList
+    // at the top left.
+    titleOffset = tester.getTopRight(find.text(title));
+    expect(titleOffset, const Offset(292.0, 136.0));
+    expect(titleOffset.dx, lessThan(wideSize.width - 320)); // Default master view width is 320.0.
+    expect(tester.getCenter(find.byType(ListView)), const Offset(160, 356));
+
+    // Configure to show the default layout.
+    await tester.binding.setSurfaceSize(defaultSize);
+  });
+
+  testWidgets('LicensePage master view layout position - rtl', (WidgetTester tester) async {
+    const TextDirection textDirection = TextDirection.rtl;
+    const Size defaultSize = Size(800.0, 600.0);
+    const Size wideSize = Size(1200.0, 600.0);
+    const String title = 'License ABC';
+    LicenseRegistry.addLicense(() {
+      return Stream<LicenseEntry>.fromIterable(<LicenseEntry>[
+        const LicenseEntryWithLineBreaks(<String>['ABC'], 'DEF'),
+      ]);
+    });
+
+    // Configure to show the default layout.
+    await tester.binding.setSurfaceSize(defaultSize);
+
+    await tester.pumpWidget(
+      const MaterialApp(
+        title: title,
+        home: Scaffold(
+          body: Directionality(
+            textDirection: textDirection,
+            child: LicensePage(),
+          ),
+        ),
+      ),
+    );
+
+    // To stop loading
+    await tester.pumpAndSettle();
+
+    // If the layout width is less than 840.0 pixels, nested layout is
+    // used which positions license page title at the top center.
+    Offset titleOffset = tester.getCenter(find.text(title));
+    expect(titleOffset, Offset(defaultSize.width / 2, 92.0));
+    expect(tester.getCenter(find.byType(ListView)), Offset(defaultSize.width / 2, 328.0));
+
+    // Configure a wide window to show the lateral UI.
+    await tester.binding.setSurfaceSize(wideSize);
+
+    await tester.pumpWidget(
+      const MaterialApp(
+        title: title,
+        home: Scaffold(
+          body: Directionality(
+            textDirection: textDirection,
+            child: LicensePage(),
+          ),
+        ),
+      ),
+    );
+
+    // To finish the FakeTimer
+    await tester.pumpAndSettle();
+
+    // If the layout width is greater than 840.0 pixels, lateral UI layout
+    // is used which positions license page title and packageList
+    // at the top right.
+    titleOffset = tester.getTopLeft(find.text(title));
+    expect(titleOffset, const Offset(908.0, 136.0));
+    expect(titleOffset.dx, greaterThan(wideSize.width - 320)); // Default master view width is 320.0.
+    expect(tester.getCenter(find.byType(ListView)), const Offset(1040.0, 356.0));
+
+    // Configure to show the default layout.
+    await tester.binding.setSurfaceSize(defaultSize);
+  });
 }
 
 class FakeLicenseEntry extends LicenseEntry {