More beautiful linear_gradient sample (#99298)

examples/api/lib/painting/gradient/linear_gradient.0.dart

@@ -11,33 +11,41 @@ void main() => runApp(const MyApp());
 class MyApp extends StatelessWidget {
   const MyApp({Key? key}) : super(key: key);
 
-  static const String _title = 'Flutter Code Sample';
-
   @override
   Widget build(BuildContext context) {
-    return const MaterialApp(
-      title: _title,
-      home: MyStatelessWidget(),
-    );
+    return const MaterialApp(home: MoodyGradient());
   }
 }
 
-class MyStatelessWidget extends StatelessWidget {
-  const MyStatelessWidget({Key? key}) : super(key: key);
+class MoodyGradient extends StatelessWidget {
+  const MoodyGradient({Key? key}) : super(key: key);
 
   @override
   Widget build(BuildContext context) {
-    return Container(
-      decoration: const BoxDecoration(
-        gradient: LinearGradient(
-          begin: Alignment.topLeft,
-          end:
-              Alignment(0.8, 0.0), // 10% of the width, so there are ten blinds.
-          colors: <Color>[
-            Color(0xffee0000),
-            Color(0xffeeee00)
-          ], // red to yellow
-          tileMode: TileMode.repeated, // repeats the gradient over the canvas
+    return Material(
+      child: Container(
+        decoration: const BoxDecoration(
+          gradient: LinearGradient(
+            begin: Alignment.topLeft,
+            end: Alignment(0.8, 1),
+            colors: <Color>[
+              Color(0xff1f005c),
+              Color(0xff5b0060),
+              Color(0xff870160),
+              Color(0xffac255e),
+              Color(0xffca485c),
+              Color(0xffe16b5c),
+              Color(0xfff39060),
+              Color(0xffffb56b),
+            ], // Gradient from https://learnui.design/tools/gradient-generator.html
+            tileMode: TileMode.mirror,
+          ),
+        ),
+        child: const Center(
+          child: Text(
+            'From Night to Day',
+            style: TextStyle(fontSize: 24, color: Colors.white),
+          ),
         ),
       ),
     );

examples/api/pubspec.yaml

@@ -25,6 +25,8 @@ dev_dependencies:
     sdk: flutter
   flutter_driver:
     sdk: flutter
+  flutter_goldens:
+    sdk: flutter
   flutter_test:
     sdk: flutter
   test: 1.20.1

examples/api/test/flutter_test_config.dart

+// Copyright 2014 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:async';
+
+import 'package:flutter_test/flutter_test.dart';
+
+import 'goldens_io.dart' if (dart.library.html) 'goldens_web.dart' as flutter_goldens;
+
+Future<void> testExecutable(FutureOr<void> Function() testMain) {
+  // Enable golden file testing using Skia Gold.
+  return flutter_goldens.testExecutable(testMain, namePrefix: 'api');
+}

examples/api/test/goldens_io.dart

+// Copyright 2014 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+export 'package:flutter_goldens/flutter_goldens.dart' show testExecutable;

examples/api/test/goldens_web.dart

+// Copyright 2014 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:async';
+
+// package:flutter_goldens is not used as part of the test process for web.
+Future<void> testExecutable(FutureOr<void> Function() testMain) async => testMain();

examples/api/test/painting/linear_gradient.0_test.dart

+// Copyright 2014 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'package:flutter/material.dart';
+import 'package:flutter/widgets.dart';
+import 'package:flutter_api_samples/painting/gradient/linear_gradient.0.dart'
+    as example;
+import 'package:flutter_test/flutter_test.dart';
+
+void main() {
+  testWidgets('finds a gradient', (WidgetTester tester) async {
+    await tester.pumpWidget(
+      const MaterialApp(
+        home: example.MoodyGradient(),
+      ),
+    );
+
+    expect(find.byType(example.MoodyGradient), findsOneWidget);
+  });
+
+  testWidgets('gradient matches golden', (WidgetTester tester) async {
+    await tester.pumpWidget(
+      const MaterialApp(
+        home: SizedBox(
+          width: 800,
+          height: 600,
+          child: RepaintBoundary(
+            child: example.MoodyGradient(),
+          ),
+        ),
+      ),
+    );
+    await expectLater(
+      find.byType(example.MoodyGradient),
+      matchesGoldenFile('linear_gradient.0_test.png'),
+    );
+  });
+}

packages/flutter/lib/src/painting/gradient.dart

@@ -349,8 +349,9 @@ abstract class Gradient {
 /// To use a [LinearGradient] to paint on a canvas directly, see [createShader].
 ///
 /// {@tool dartpad}
-/// This sample draws a picture that looks like vertical window shades by having
-/// a [Container] display a [BoxDecoration] with a [LinearGradient].
+/// This sample draws a picture with a gradient sweeping through different
+/// colors, by having a [Container] display a [BoxDecoration] with a
+/// [LinearGradient].
 ///
 /// ** See code in examples/api/lib/painting/gradient/linear_gradient.0.dart **
 /// {@end-tool}

packages/flutter_goldens/lib/flutter_goldens.dart

@@ -25,15 +25,18 @@ const String _kFlutterRootKey = 'FLUTTER_ROOT';
 /// [goldenFileComparator] to an instance of [FlutterGoldenFileComparator] that
 /// works for the current test. _Which_ FlutterGoldenFileComparator is
 /// instantiated is based on the current testing environment.
-Future<void> testExecutable(FutureOr<void> Function() testMain) async {
+///
+/// When set, the `namePrefix` is prepended to the names of all gold images.
+Future<void> testExecutable(FutureOr<void> Function() testMain, {String? namePrefix}) async {
   const Platform platform = LocalPlatform();
   if (FlutterPostSubmitFileComparator.isAvailableForEnvironment(platform)) {
-    goldenFileComparator = await FlutterPostSubmitFileComparator.fromDefaultComparator(platform);
+    goldenFileComparator = await FlutterPostSubmitFileComparator.fromDefaultComparator(platform, namePrefix: namePrefix);
   } else if (FlutterPreSubmitFileComparator.isAvailableForEnvironment(platform)) {
-    goldenFileComparator = await FlutterPreSubmitFileComparator.fromDefaultComparator(platform);
+    goldenFileComparator = await FlutterPreSubmitFileComparator.fromDefaultComparator(platform, namePrefix: namePrefix);
   } else if (FlutterSkippingFileComparator.isAvailableForEnvironment(platform)) {
     goldenFileComparator = FlutterSkippingFileComparator.fromDefaultComparator(
-      'Golden file testing is not executed on Cirrus, or LUCI environments outside of flutter/flutter.'
+      'Golden file testing is not executed on Cirrus, or LUCI environments outside of flutter/flutter.',
+        namePrefix: namePrefix
     );
   } else {
     goldenFileComparator = await FlutterLocalFileComparator.fromDefaultComparator(platform);
@@ -91,6 +94,7 @@ abstract class FlutterGoldenFileComparator extends GoldenFileComparator {
     this.skiaClient, {
     this.fs = const LocalFileSystem(),
     this.platform = const LocalPlatform(),
+    this.namePrefix,
   });
 
   /// The directory to which golden file URIs will be resolved in [compare] and
@@ -109,6 +113,9 @@ abstract class FlutterGoldenFileComparator extends GoldenFileComparator {
   @visibleForTesting
   final Platform platform;
 
+  /// The prefix that is added to all golden names.
+  final String? namePrefix;
+
   @override
   Future<void> update(Uri golden, Uint8List imageBytes) async {
     final File goldenFile = getGoldenFile(golden);
@@ -173,8 +180,12 @@ abstract class FlutterGoldenFileComparator extends GoldenFileComparator {
       'Golden files in the Flutter framework must end with the file extension '
       '.png.'
     );
-    final String prefix = basedir.pathSegments[basedir.pathSegments.length - 2];
-    return Uri.parse('$prefix.$golden');
+    return Uri.parse(<String>[
+      if (namePrefix != null)
+        namePrefix!,
+      basedir.pathSegments[basedir.pathSegments.length - 2],
+      golden.toString(),
+    ].join('.'));
   }
 }
 
@@ -205,11 +216,13 @@ class FlutterPostSubmitFileComparator extends FlutterGoldenFileComparator {
     final SkiaGoldClient skiaClient, {
     final FileSystem fs = const LocalFileSystem(),
     final Platform platform = const LocalPlatform(),
+    String? namePrefix,
   }) : super(
     basedir,
     skiaClient,
     fs: fs,
     platform: platform,
+    namePrefix: namePrefix,
   );
 
   /// Creates a new [FlutterPostSubmitFileComparator] that mirrors the relative
@@ -221,6 +234,7 @@ class FlutterPostSubmitFileComparator extends FlutterGoldenFileComparator {
     final Platform platform, {
     SkiaGoldClient? goldens,
     LocalFileComparator? defaultComparator,
+    String? namePrefix,
   }) async {
 
     defaultComparator ??= goldenFileComparator as LocalFileComparator;
@@ -233,7 +247,7 @@ class FlutterPostSubmitFileComparator extends FlutterGoldenFileComparator {
 
     goldens ??= SkiaGoldClient(baseDirectory);
     await goldens.auth();
-    return FlutterPostSubmitFileComparator(baseDirectory.uri, goldens);
+    return FlutterPostSubmitFileComparator(baseDirectory.uri, goldens, namePrefix: namePrefix);
   }
 
   @override
@@ -283,11 +297,13 @@ class FlutterPreSubmitFileComparator extends FlutterGoldenFileComparator {
     final SkiaGoldClient skiaClient, {
     final FileSystem fs = const LocalFileSystem(),
     final Platform platform = const LocalPlatform(),
+    final String? namePrefix,
   }) : super(
     basedir,
     skiaClient,
     fs: fs,
     platform: platform,
+    namePrefix: namePrefix,
   );
 
   /// Creates a new [FlutterPreSubmitFileComparator] that mirrors the
@@ -300,6 +316,7 @@ class FlutterPreSubmitFileComparator extends FlutterGoldenFileComparator {
     SkiaGoldClient? goldens,
     LocalFileComparator? defaultComparator,
     Directory? testBasedir,
+    String? namePrefix,
   }) async {
 
     defaultComparator ??= goldenFileComparator as LocalFileComparator;
@@ -318,6 +335,7 @@ class FlutterPreSubmitFileComparator extends FlutterGoldenFileComparator {
     return FlutterPreSubmitFileComparator(
       baseDirectory.uri,
       goldens, platform: platform,
+      namePrefix: namePrefix,
     );
   }
 
@@ -367,8 +385,9 @@ class FlutterSkippingFileComparator extends FlutterGoldenFileComparator {
   FlutterSkippingFileComparator(
     final Uri basedir,
     final SkiaGoldClient skiaClient,
-    this.reason,
-  ) : super(basedir, skiaClient);
+    this.reason, {
+    String? namePrefix,
+  }) : super(basedir, skiaClient, namePrefix: namePrefix);
 
   /// Describes the reason for using the [FlutterSkippingFileComparator].
   ///
@@ -380,12 +399,13 @@ class FlutterSkippingFileComparator extends FlutterGoldenFileComparator {
   static FlutterSkippingFileComparator fromDefaultComparator(
     String reason, {
     LocalFileComparator? defaultComparator,
+    String? namePrefix,
   }) {
     defaultComparator ??= goldenFileComparator as LocalFileComparator;
     const FileSystem fs = LocalFileSystem();
     final Uri basedir = defaultComparator.basedir;
     final SkiaGoldClient skiaClient = SkiaGoldClient(fs.directory(basedir));
-    return FlutterSkippingFileComparator(basedir, skiaClient, reason);
+    return FlutterSkippingFileComparator(basedir, skiaClient, reason, namePrefix: namePrefix);
   }
 
   @override

packages/flutter_goldens/test/flutter_goldens_test.dart

@@ -466,6 +466,27 @@ void main() {
       expect(key, Uri.parse('foo.png'));
     });
 
+    test('adds namePrefix', () async {
+      const String libraryName = 'sidedishes';
+      const String namePrefix = 'tomatosalad';
+      const String fileName = 'lettuce.png';
+      final FakeSkiaGoldClient fakeSkiaClient = FakeSkiaGoldClient();
+      final Directory basedir = fs.directory('flutter/test/$libraryName/')
+        ..createSync(recursive: true);
+      final FlutterGoldenFileComparator comparator = FlutterPostSubmitFileComparator(
+        basedir.uri,
+        fakeSkiaClient,
+        fs: fs,
+        platform: platform,
+        namePrefix: namePrefix,
+      );
+      await comparator.compare(
+        Uint8List.fromList(_kTestPngBytes),
+        Uri.parse(fileName),
+      );
+      expect(fakeSkiaClient.testNames.single, '$namePrefix.$libraryName.$fileName');
+    });
+
     group('Post-Submit', () {
       late FakeSkiaGoldClient fakeSkiaClient;
 
@@ -926,11 +947,16 @@ class FakeSkiaGoldClient extends Fake implements SkiaGoldClient {
   @override
   Future<void> auth() async {}
 
+  final List<String> testNames = <String>[];
+
   int initCalls = 0;
   @override
   Future<void> imgtestInit() async => initCalls += 1;
   @override
-  Future<bool> imgtestAdd(String testName, File goldenFile) async => true;
+  Future<bool> imgtestAdd(String testName, File goldenFile) async {
+    testNames.add(testName);
+    return true;
+  }
 
   int tryInitCalls = 0;
   @override