Fix Pesto appbar heroics (#5447)

examples/flutter_gallery/lib/demo/pesto_demo.dart

@@ -9,11 +9,9 @@ import 'package:flutter/material.dart';
 const String _kUserName = 'Jonathan';
 const String _kUserEmail = 'jonathan@example.com';
 const String _kUserImage = 'packages/flutter_gallery_assets/pesto/avatar.jpg';
-// Map of logo images keyed by the minimum height their container needs to be.
-final Map<double, String> _kLogoImages = <double, String>{
-  0.0: 'packages/flutter_gallery_assets/pesto/logo_small.png',
-  70.0: 'packages/flutter_gallery_assets/pesto/logo_medium.png'
-};
+
+const String _kSmallLogoImage = 'packages/flutter_gallery_assets/pesto/logo_small.png';
+const String _kMediumLogoImage = 'packages/flutter_gallery_assets/pesto/logo_medium.png';
 
 final ThemeData _kTheme = new ThemeData(
   brightness: Brightness.light,
@@ -94,20 +92,18 @@ class _PestoDemoState extends State<PestoDemo> {
       flexibleSpace: new LayoutBuilder(
         builder: (BuildContext context, BoxConstraints constraints) {
           final Size size = constraints.biggest;
-          double appBarHeight = size.height - statusBarHeight;
-          double bestHeight = _kLogoImages.keys.lastWhere(
-            (double height) => appBarHeight >= height
-          );
+          final double appBarHeight = size.height - statusBarHeight;
+          final String logo = appBarHeight >= 70.0 ? _kMediumLogoImage : _kSmallLogoImage;
           // Extra padding. Calculated to give about 16px on the bottom for the
           // `small` logo at its native size, and 30px for the `medium`.
-          double extraPadding = min(0.19 * appBarHeight + 5.4, 40.0);
+          final double extraPadding = min(0.19 * appBarHeight + 5.4, 40.0);
           return new Padding(
             padding: new EdgeInsets.only(
               top: statusBarHeight + 0.5 * extraPadding,
               bottom: extraPadding
             ),
             child: new Center(
-              child: new Image.asset(_kLogoImages[bestHeight], fit: ImageFit.scaleDown)
+              child: new Image.asset(logo, fit: ImageFit.scaleDown)
             )
           );
         }

examples/flutter_gallery/test/pesto_test.dart

@@ -4,7 +4,7 @@
 
 import 'package:flutter/material.dart';
 import 'package:flutter_test/flutter_test.dart';
-import 'package:flutter_gallery/main.dart' as flutter_gallery_main;
+import 'package:flutter_gallery/gallery/app.dart';
 
 Finder byTooltip(WidgetTester tester, String message) {
   return find.byWidgetPredicate((Widget widget) {
@@ -17,14 +17,13 @@ Finder findNavigationMenuButton(WidgetTester tester) {
 }
 
 void main() {
-  TestWidgetsFlutterBinding binding =
-      TestWidgetsFlutterBinding.ensureInitialized();
-  if (binding is LiveTestWidgetsFlutterBinding) binding.allowAllFrames = true;
+  TestWidgetsFlutterBinding binding = TestWidgetsFlutterBinding.ensureInitialized();
+  if (binding is LiveTestWidgetsFlutterBinding)
+    binding.allowAllFrames = true;
 
   // Regression test for https://github.com/flutter/flutter/pull/5168
   testWidgets('Pesto route management', (WidgetTester tester) async {
-    flutter_gallery_main
-        .main(); // builds the app and schedules a frame but doesn't trigger one
+    await tester.pumpWidget(new GalleryApp());
     await tester.pump(); // see https://github.com/flutter/flutter/issues/1865
     await tester.pump(); // triggers a frame
 
@@ -52,4 +51,35 @@ void main() {
 
     expect(find.text('Flutter Gallery'), findsOneWidget);
   });
+
+  // Regression test for https://github.com/flutter/flutter/pull/5168
+  testWidgets('Pesto appbar heroics', (WidgetTester tester) async {
+    await tester.pumpWidget(
+      // The bug only manifests itself when the screen's orientation is portait
+      new Center(
+        child: new SizedBox(
+          width: 400.0,
+          height: 800.0,
+          child: new GalleryApp()
+        )
+      )
+    );
+    await tester.pump(); // see https://github.com/flutter/flutter/issues/1865
+    await tester.pump(); // triggers a frame
+
+    await tester.tap(find.text('Pesto'));
+    await tester.pump(); // Launch pesto
+    await tester.pump(const Duration(seconds: 1)); // transition is complete
+
+    await tester.tap(find.text('Pesto Bruchetta'));
+    await tester.pump(); // Launch the recipe page
+    await tester.pump(const Duration(seconds: 1)); // transition is complete
+
+    await tester.scroll(find.text('Pesto Bruchetta'), const Offset(0.0, -300.0));
+    await tester.pump();
+
+    Navigator.pop(find.byType(Scaffold).evaluate().single);
+    await tester.pump();
+    await tester.pump(const Duration(seconds: 1)); // transition is complete
+  });
 }