Screenshot improvements (#7800)

Add an "s" command to `flutter run` which takes a screenshot.
Make that comment turn off the slow mode banner.

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

@@ -119,6 +119,14 @@ class WidgetsApp extends StatefulWidget {
   /// Used by `showPerformanceOverlay` observatory extension.
   static bool showPerformanceOverlayOverride = false;
 
+  /// If false, prevents the debug banner from being visible.
+  ///
+  /// Used by `debugAllowBanner` observatory extension.
+  ///
+  /// This is how `flutter run` turns off the banner when you take a screen shot
+  /// with "s".
+  static bool debugAllowBannerOverride = true;
+
   @override
   _WidgetsAppState createState() => new _WidgetsAppState();
 }
@@ -231,7 +239,7 @@ class _WidgetsAppState extends State<WidgetsApp> implements WidgetsBindingObserv
       );
     }
     assert(() {
-      if (config.debugShowCheckedModeBanner) {
+      if (config.debugShowCheckedModeBanner && WidgetsApp.debugAllowBannerOverride) {
         result = new CheckedModeBanner(
           child: result
         );

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

@@ -89,6 +89,17 @@ abstract class WidgetsBinding extends BindingBase implements GestureBinding, Ren
         buildOwner.reassemble(renderViewElement);
       }
     );
+
+    registerBoolServiceExtension(
+      name: 'debugAllowBanner',
+      getter: () => WidgetsApp.debugAllowBannerOverride,
+      setter: (bool value) {
+        if (WidgetsApp.debugAllowBannerOverride == value)
+          return;
+        WidgetsApp.debugAllowBannerOverride = value;
+        buildOwner.reassemble(renderViewElement);
+      }
+    );
   }
 
   /// The [BuildOwner] in charge of executing the build pipeline for the

packages/flutter/test/widgets/app_overrides_test.dart

+// Copyright 2017 The Chromium 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_test/flutter_test.dart';
+import 'package:flutter/widgets.dart';
+
+class TestRoute<T> extends PageRoute<T> {
+  TestRoute({ this.child, RouteSettings settings }) : super(settings: settings);
+
+  final Widget child;
+
+  @override
+  Duration get transitionDuration => const Duration(milliseconds: 150);
+
+  @override
+  Color get barrierColor => null;
+
+  @override
+  bool get maintainState => false;
+
+  @override
+  Widget buildPage(BuildContext context, Animation<double> animation, Animation<double> forwardAnimation) {
+    return child;
+  }
+}
+
+Future<Null> pumpApp(WidgetTester tester) async {
+  await tester.pumpWidget(new WidgetsApp(
+    color: const Color(0xFF333333),
+    onGenerateRoute: (RouteSettings settings) {
+      return new TestRoute<Null>(settings: settings, child: new Container());
+    },
+  ));
+}
+
+void main() {
+  testWidgets('WidgetsApp control test', (WidgetTester tester) async {
+    await pumpApp(tester);
+    expect(find.byType(WidgetsApp), findsOneWidget);
+    expect(find.byType(Navigator), findsOneWidget);
+    expect(find.byType(PerformanceOverlay), findsNothing);
+    expect(find.byType(CheckedModeBanner), findsOneWidget);
+  });
+
+  testWidgets('showPerformanceOverlayOverride true', (WidgetTester tester) async {
+    expect(WidgetsApp.showPerformanceOverlayOverride, false);
+    WidgetsApp.showPerformanceOverlayOverride = true;
+    await pumpApp(tester);
+    expect(find.byType(WidgetsApp), findsOneWidget);
+    expect(find.byType(Navigator), findsOneWidget);
+    expect(find.byType(PerformanceOverlay), findsOneWidget);
+    expect(find.byType(CheckedModeBanner), findsOneWidget);
+  });
+
+  testWidgets('showPerformanceOverlayOverride false', (WidgetTester tester) async {
+    expect(WidgetsApp.showPerformanceOverlayOverride, true);
+    WidgetsApp.showPerformanceOverlayOverride = false;
+    await pumpApp(tester);
+    expect(find.byType(WidgetsApp), findsOneWidget);
+    expect(find.byType(Navigator), findsOneWidget);
+    expect(find.byType(PerformanceOverlay), findsNothing);
+    expect(find.byType(CheckedModeBanner), findsOneWidget);
+  });
+
+  testWidgets('debugAllowBannerOverride false', (WidgetTester tester) async {
+    expect(WidgetsApp.showPerformanceOverlayOverride, false);
+    expect(WidgetsApp.debugAllowBannerOverride, true);
+    WidgetsApp.debugAllowBannerOverride = false;
+    await pumpApp(tester);
+    expect(find.byType(WidgetsApp), findsOneWidget);
+    expect(find.byType(Navigator), findsOneWidget);
+    expect(find.byType(PerformanceOverlay), findsNothing);
+    expect(find.byType(CheckedModeBanner), findsNothing);
+  });
+
+  testWidgets('debugAllowBannerOverride true', (WidgetTester tester) async {
+    expect(WidgetsApp.showPerformanceOverlayOverride, false);
+    expect(WidgetsApp.debugAllowBannerOverride, false);
+    WidgetsApp.debugAllowBannerOverride = true;
+    await pumpApp(tester);
+    expect(find.byType(WidgetsApp), findsOneWidget);
+    expect(find.byType(Navigator), findsOneWidget);
+    expect(find.byType(PerformanceOverlay), findsNothing);
+    expect(find.byType(CheckedModeBanner), findsOneWidget);
+  });
+}

packages/flutter_tools/lib/src/commands/screenshot.dart

@@ -139,7 +139,7 @@ class ScreenshotCommand extends FlutterCommand {
   }
 
   Future<Null> showOutputFileInfo(File outputFile) async {
-    int sizeKB = (await outputFile.length()) ~/ 1000;
-    printStatus('Screenshot written to ${path.relative(outputFile.path)} (${sizeKB}kb).');
+    int sizeKB = (await outputFile.length()) ~/ 1024;
+    printStatus('Screenshot written to ${path.relative(outputFile.path)} (${sizeKB}kB).');
   }
 }

packages/flutter_tools/lib/src/resident_runner.dart

@@ -7,17 +7,14 @@ import 'dart:async';
 import 'package:meta/meta.dart';
 import 'package:path/path.dart' as path;
 
-
 import 'application_package.dart';
-
-import 'base/file_system.dart';
-import 'base/io.dart';
-import 'base/os.dart';
-
 import 'asset.dart';
-
 import 'base/common.dart';
+import 'base/file_system.dart';
+import 'base/io.dart';
 import 'base/logger.dart';
+import 'base/os.dart';
+import 'base/utils.dart';
 import 'build_info.dart';
 import 'dart/dependencies.dart';
 import 'dart/package_map.dart';
@@ -110,6 +107,24 @@ abstract class ResidentRunner {
     await currentView.uiIsolate.flutterToggleDebugPaintSizeEnabled();
   }
 
+  Future<Null> _screenshot() async {
+    File outputFile = getUniqueFile(fs.currentDirectory, 'flutter', 'png');
+    try {
+      if (vmService != null)
+        await vmService.vm.refreshViews();
+      if (isRunningDebug)
+        await currentView.uiIsolate.flutterDebugAllowBanner(false);
+      if (!await device.takeScreenshot(outputFile))
+        printError('Error taking screenshot.');
+      if (isRunningDebug)
+        await currentView.uiIsolate.flutterDebugAllowBanner(true);
+      int sizeKB = (await outputFile.length()) ~/ 1024;
+      printStatus('Screenshot written to ${path.relative(outputFile.path)} (${sizeKB}kB).');
+    } catch (error) {
+      printError('Error taking screenshot: $error');
+    }
+  }
+
   void registerSignalHandlers() {
     assert(stayResident);
     ProcessSignal.SIGINT.watch().listen(_cleanUpAndExit);
@@ -212,6 +227,11 @@ abstract class ResidentRunner {
         return true;
       await _debugToggleDebugPaintSizeEnabled();
       return true;
+    } else if (lower == 's') {
+      if (!supportsServiceProtocol || !device.supportsScreenshot)
+        return true;
+      await _screenshot();
+      return true;
     } else if (lower == 'q' || character == AnsiTerminal.KEY_F10) {
       // F10, exit
       await stop();
@@ -309,9 +329,13 @@ abstract class ResidentRunner {
   void printHelp({ @required bool details });
 
   void printHelpDetails() {
-    printStatus('To dump the widget hierarchy of the app (debugDumpApp), press "w".');
-    printStatus('To dump the rendering tree of the app (debugDumpRenderTree), press "t".');
-    printStatus('To toggle the display of construction lines (debugPaintSizeEnabled), press "p".');
+    if (supportsServiceProtocol) {
+      printStatus('To dump the widget hierarchy of the app (debugDumpApp), press "w".');
+      printStatus('To dump the rendering tree of the app (debugDumpRenderTree), press "t".');
+      printStatus('To toggle the display of construction lines (debugPaintSizeEnabled), press "p".');
+    }
+    if (device.supportsScreenshot)
+      printStatus('To save a screenshot to flutter.png, press "s".');
   }
 
   /// Called when a signal has requested we exit.

packages/flutter_tools/lib/src/vmservice.dart

@@ -836,6 +836,10 @@ class Isolate extends ServiceObjectOwner {
     return state;
   }
 
+  Future<Null> flutterDebugAllowBanner(bool show) async {
+    await invokeFlutterExtensionRpcRaw('ext.flutter.debugAllowBanner', params: <String, dynamic>{ 'enabled': show });
+  }
+
   // Reload related extension methods.
   Future<Map<String, dynamic>> flutterReassemble() async {
     return await invokeFlutterExtensionRpcRaw('ext.flutter.reassemble',