dev/benchmarks/macrobenchmarks/lib/web_benchmarks.dart - external/github.com/flutter/flutter - Git at Google

 // 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 'dart:convert' show json;
 import 'dart:html' as html;
 import 'dart:math' as math;

 import 'package:macrobenchmarks/src/web/bench_text_layout.dart';
 import 'package:macrobenchmarks/src/web/bench_text_out_of_picture_bounds.dart';

 import 'package:gallery/benchmarks/gallery_automator.dart' show DemoType, typeOfDemo;

 import 'src/web/bench_build_image.dart';
 import 'src/web/bench_build_material_checkbox.dart';
 import 'src/web/bench_card_infinite_scroll.dart';
 import 'src/web/bench_child_layers.dart';
 import 'src/web/bench_clipped_out_pictures.dart';
 import 'src/web/bench_draw_rect.dart';
 import 'src/web/bench_dynamic_clip_on_static_picture.dart';
 import 'src/web/bench_mouse_region_grid_hover.dart';
 import 'src/web/bench_mouse_region_grid_scroll.dart';
 import 'src/web/bench_mouse_region_mixed_grid_hover.dart';
 import 'src/web/bench_paths.dart';
 import 'src/web/bench_picture_recording.dart';
 import 'src/web/bench_simple_lazy_text_scroll.dart';
 import 'src/web/bench_text_out_of_picture_bounds.dart';
 import 'src/web/gallery/gallery_recorder.dart';
 import 'src/web/recorder.dart';

 typedef RecorderFactory = Recorder Function();

 const bool isCanvasKit = bool.fromEnvironment('FLUTTER_WEB_USE_SKIA', defaultValue: false);

 const String _galleryBenchmarkPrefix = 'gallery_v2';

 /// List of all benchmarks that run in the devicelab.
 ///
 /// When adding a new benchmark, add it to this map. Make sure that the name
 /// of your benchmark is unique.
 final Map<String, RecorderFactory> benchmarks = <String, RecorderFactory>{
   BenchBuildImage.benchmarkName: () => BenchBuildImage(),
   BenchCardInfiniteScroll.benchmarkName: () => BenchCardInfiniteScroll.forward(),
   BenchCardInfiniteScroll.benchmarkNameBackward: () => BenchCardInfiniteScroll.backward(),
   BenchClippedOutPictures.benchmarkName: () => BenchClippedOutPictures(),
   BenchDrawRect.benchmarkName: () => BenchDrawRect.staticPaint(),
   BenchDrawRect.variablePaintBenchmarkName: () => BenchDrawRect.variablePaint(),
   BenchPathRecording.benchmarkName: () => BenchPathRecording(),
   BenchTextOutOfPictureBounds.benchmarkName: () => BenchTextOutOfPictureBounds(),
   BenchSimpleLazyTextScroll.benchmarkName: () => BenchSimpleLazyTextScroll(),
   BenchBuildMaterialCheckbox.benchmarkName: () => BenchBuildMaterialCheckbox(),
   BenchDynamicClipOnStaticPicture.benchmarkName: () => BenchDynamicClipOnStaticPicture(),
   BenchPictureRecording.benchmarkName: () => BenchPictureRecording(),
   BenchUpdateManyChildLayers.benchmarkName: () => BenchUpdateManyChildLayers(),
   BenchMouseRegionGridScroll.benchmarkName: () => BenchMouseRegionGridScroll(),
   BenchMouseRegionGridHover.benchmarkName: () => BenchMouseRegionGridHover(),
   BenchMouseRegionMixedGridHover.benchmarkName: () => BenchMouseRegionMixedGridHover(),
   if (isCanvasKit)
     BenchBuildColorsGrid.canvasKitBenchmarkName: () => BenchBuildColorsGrid.canvasKit(),

   // Benchmarks that we don't want to run using CanvasKit.
   if (!isCanvasKit) ...<String, RecorderFactory>{
     BenchTextLayout.domBenchmarkName: () => BenchTextLayout(useCanvas: false),
     BenchTextLayout.canvasBenchmarkName: () => BenchTextLayout(useCanvas: true),
     BenchTextCachedLayout.domBenchmarkName: () => BenchTextCachedLayout(useCanvas: false),
     BenchTextCachedLayout.canvasBenchmarkName: () => BenchTextCachedLayout(useCanvas: true),
     BenchBuildColorsGrid.domBenchmarkName: () => BenchBuildColorsGrid.dom(),
     BenchBuildColorsGrid.canvasBenchmarkName: () => BenchBuildColorsGrid.canvas(),

     // The following benchmark is for the Flutter Gallery.
     // This benchmark is failing when run with CanvasKit, so we skip it
     // for now.
     // TODO(yjbanov): https://github.com/flutter/flutter/issues/59082
     '${_galleryBenchmarkPrefix}_studies_perf': () => GalleryRecorder(
       benchmarkName: '${_galleryBenchmarkPrefix}_studies_perf',
       shouldRunPredicate: (String demo) => typeOfDemo(demo) == DemoType.study,
     ),
     '${_galleryBenchmarkPrefix}_unanimated_perf': () => GalleryRecorder(
       benchmarkName: '${_galleryBenchmarkPrefix}_unanimated_perf',
       shouldRunPredicate: (String demo) => typeOfDemo(demo) == DemoType.unanimatedWidget,
     ),
     '${_galleryBenchmarkPrefix}_animated_perf': () => GalleryRecorder(
       benchmarkName: '${_galleryBenchmarkPrefix}_animated_perf',
       shouldRunPredicate: (String demo) => typeOfDemo(demo) == DemoType.animatedWidget,
     ),
     '${_galleryBenchmarkPrefix}_scroll_perf': () => GalleryRecorder(
       benchmarkName: '${_galleryBenchmarkPrefix}_scroll_perf',
       testScrollsOnly: true,
     ),
   },
 };

 final LocalBenchmarkServerClient _client = LocalBenchmarkServerClient();

 Future<void> main() async {
   // Check if the benchmark server wants us to run a specific benchmark.
   final String nextBenchmark = await _client.requestNextBenchmark();

   if (nextBenchmark == LocalBenchmarkServerClient.kManualFallback) {
     _fallbackToManual('The server did not tell us which benchmark to run next.');
     return;
   }

   await _runBenchmark(nextBenchmark);
   html.window.location.reload();
 }

 Future<void> _runBenchmark(String benchmarkName) async {
   final RecorderFactory recorderFactory = benchmarks[benchmarkName];

   if (recorderFactory == null) {
     _fallbackToManual('Benchmark $benchmarkName not found.');
     return;
   }

   await runZoned<Future<void>>(
     () async {
       final Recorder recorder = recorderFactory();
       final Runner runner = recorder.isTracingEnabled && !_client.isInManualMode
           ? Runner(
               recorder: recorder,
               setUpAllDidRun: () => _client.startPerformanceTracing(benchmarkName),
               tearDownAllWillRun: _client.stopPerformanceTracing,
             )
           : Runner(recorder: recorder);

       final Profile profile = await runner.run();
       if (!_client.isInManualMode) {
         await _client.sendProfileData(profile);
       } else {
         _printResultsToScreen(profile);
         print(profile);
       }
     },
     zoneSpecification: ZoneSpecification(
       print: (Zone self, ZoneDelegate parent, Zone zone, String line) async {
         if (_client.isInManualMode) {
           parent.print(zone, '[$benchmarkName] $line');
         } else {
           await _client.printToConsole(line);
         }
       },
       handleUncaughtError: (
         Zone self,
         ZoneDelegate parent,
         Zone zone, Object error,
         StackTrace stackTrace,
       ) async {
         if (_client.isInManualMode) {
           parent.print(zone, '[$benchmarkName] $error, $stackTrace');
           parent.handleUncaughtError(zone, error, stackTrace);
         } else {
           await _client.reportError(error, stackTrace);
         }
       },
     ),
   );
 }

 void _fallbackToManual(String error) {
   html.document.body.appendHtml('''
     <div id="manual-panel">
       <h3>$error</h3>

       <p>Choose one of the following benchmarks:</p>

       <!-- Absolutely position it so it receives the clicks and not the glasspane -->
       <ul style="position: absolute">
         ${
           benchmarks.keys
             .map((String name) => '<li><button id="$name">$name</button></li>')
             .join('\n')
         }
       </ul>
     </div>
   ''', validator: html.NodeValidatorBuilder()..allowHtml5()..allowInlineStyles());

   for (final String benchmarkName in benchmarks.keys) {
     final html.Element button = html.document.querySelector('#$benchmarkName');
     button.addEventListener('click', (_) {
       final html.Element manualPanel = html.document.querySelector('#manual-panel');
       manualPanel?.remove();
       _runBenchmark(benchmarkName);
     });
   }
 }

 /// Visualizes results on the Web page for manual inspection.
 void _printResultsToScreen(Profile profile) {
   html.document.body.remove();
   html.document.body = html.BodyElement();
   html.document.body.appendHtml('<h2>${profile.name}</h2>');

   profile.scoreData.forEach((String scoreKey, Timeseries timeseries) {
     html.document.body.appendHtml('<h2>$scoreKey</h2>');
     html.document.body.appendHtml('<pre>${timeseries.computeStats()}</pre>');
     html.document.body.append(TimeseriesVisualization(timeseries).render());
   });
 }

 /// Draws timeseries data and statistics on a canvas.
 class TimeseriesVisualization {
   TimeseriesVisualization(this._timeseries) {
     _stats = _timeseries.computeStats();
     _canvas = html.CanvasElement();
     _screenWidth = html.window.screen.width;
     _canvas.width = _screenWidth;
     _canvas.height = (_kCanvasHeight * html.window.devicePixelRatio).round();
     _canvas.style
       ..width = '100%'
       ..height = '${_kCanvasHeight}px'
       ..outline = '1px solid green';
     _ctx = _canvas.context2D;

     // The amount of vertical space available on the chart. Because some
     // outliers can be huge they can dwarf all the useful values. So we
     // limit it to 1.5 x the biggest non-outlier.
     _maxValueChartRange = 1.5 * _stats.samples
       .where((AnnotatedSample sample) => !sample.isOutlier)
       .map<double>((AnnotatedSample sample) => sample.magnitude)
       .fold<double>(0, math.max);
   }

   static const double _kCanvasHeight = 200;

   final Timeseries _timeseries;
   TimeseriesStats _stats;
   html.CanvasElement _canvas;
   html.CanvasRenderingContext2D _ctx;
   int _screenWidth;

   // Used to normalize benchmark values to chart height.
   double _maxValueChartRange;

   /// Converts a sample value to vertical canvas coordinates.
   ///
   /// This does not work for horizontal coordinates.
   double _normalized(double value) {
     return _kCanvasHeight * value / _maxValueChartRange;
   }

   /// A utility for drawing lines.
   void drawLine(num x1, num y1, num x2, num y2) {
     _ctx.beginPath();
     _ctx.moveTo(x1, y1);
     _ctx.lineTo(x2, y2);
     _ctx.stroke();
   }

   /// Renders the timeseries into a `<canvas>` and returns the canvas element.
   html.CanvasElement render() {
     _ctx.translate(0, _kCanvasHeight * html.window.devicePixelRatio);
     _ctx.scale(1, -html.window.devicePixelRatio);

     final double barWidth = _screenWidth / _stats.samples.length;
     double xOffset = 0;
     for (int i = 0; i < _stats.samples.length; i++) {
       final AnnotatedSample sample = _stats.samples[i];

       if (sample.isWarmUpValue) {
         // Put gray background behing warm-up samples.
         _ctx.fillStyle = 'rgba(200,200,200,1)';
         _ctx.fillRect(xOffset, 0, barWidth, _normalized(_maxValueChartRange));
       }

       if (sample.magnitude > _maxValueChartRange) {
         // The sample value is so big it doesn't fit on the chart. Paint it purple.
         _ctx.fillStyle = 'rgba(100,50,100,0.8)';
       } else if (sample.isOutlier) {
         // The sample is an outlier, color it light red.
         _ctx.fillStyle = 'rgba(255,50,50,0.6)';
       } else {
         // A non-outlier sample, color it light blue.
         _ctx.fillStyle = 'rgba(50,50,255,0.6)';
       }

       _ctx.fillRect(xOffset, 0, barWidth - 1, _normalized(sample.magnitude));
       xOffset += barWidth;
     }

     // Draw a horizontal solid line corresponding to the average.
     _ctx.lineWidth = 1;
     drawLine(0, _normalized(_stats.average), _screenWidth, _normalized(_stats.average));

     // Draw a horizontal dashed line corresponding to the outlier cut off.
     _ctx.setLineDash(<num>[5, 5]);
     drawLine(0, _normalized(_stats.outlierCutOff), _screenWidth, _normalized(_stats.outlierCutOff));

     // Draw a light red band that shows the noise (1 stddev in each direction).
     _ctx.fillStyle = 'rgba(255,50,50,0.3)';
     _ctx.fillRect(
       0,
       _normalized(_stats.average * (1 - _stats.noise)),
       _screenWidth,
       _normalized(2 * _stats.average * _stats.noise),
     );

     return _canvas;
   }
 }

 /// Implements the client REST API for the local benchmark server.
 ///
 /// The local server is optional. If it is not available the benchmark UI must
 /// implement a manual fallback. This allows debugging benchmarks using plain
 /// `flutter run`.
 class LocalBenchmarkServerClient {
   /// This value is returned by [requestNextBenchmark].
   static const String kManualFallback = '__manual_fallback__';

   /// Whether we fell back to manual mode.
   ///
   /// This happens when you run benchmarks using plain `flutter run` rather than
   /// devicelab test harness. The test harness spins up a special server that
   /// provides API for automatically picking the next benchmark to run.
   bool isInManualMode;

   /// Asks the local server for the name of the next benchmark to run.
   ///
   /// Returns [kManualFallback] if local server is not available (uses 404 as a
   /// signal).
   Future<String> requestNextBenchmark() async {
     final html.HttpRequest request = await _requestXhr(
       '/next-benchmark',
       method: 'POST',
       mimeType: 'application/json',
       sendData: json.encode(benchmarks.keys.toList()),
     );

     // 404 is expected in the following cases:
     // - The benchmark is ran using plain `flutter run`, which does not provide "next-benchmark" handler.
     // - We ran all benchmarks and the benchmark is telling us there are no more benchmarks to run.
     if (request.status == 404) {
       isInManualMode = true;
       return kManualFallback;
     }

     isInManualMode = false;
     return request.responseText;
   }

   void _checkNotManualMode() {
     if (isInManualMode) {
       throw StateError('Operation not supported in manual fallback mode.');
     }
   }

   /// Asks the local server to begin tracing performance.
   ///
   /// This uses the chrome://tracing tracer, which is not available from within
   /// the page itself, and therefore must be controlled from outside using the
   /// DevTools Protocol.
   Future<void> startPerformanceTracing(String benchmarkName) async {
     _checkNotManualMode();
     await html.HttpRequest.request(
       '/start-performance-tracing?label=$benchmarkName',
       method: 'POST',
       mimeType: 'application/json',
     );
   }

   /// Stops the performance tracing session started by [startPerformanceTracing].
   Future<void> stopPerformanceTracing() async {
     _checkNotManualMode();
     await html.HttpRequest.request(
       '/stop-performance-tracing',
       method: 'POST',
       mimeType: 'application/json',
     );
   }

   /// Sends the profile data collected by the benchmark to the local benchmark
   /// server.
   Future<void> sendProfileData(Profile profile) async {
     _checkNotManualMode();
     final html.HttpRequest request = await html.HttpRequest.request(
       '/profile-data',
       method: 'POST',
       mimeType: 'application/json',
       sendData: json.encode(profile.toJson()),
     );
     if (request.status != 200) {
       throw Exception(
         'Failed to report profile data to benchmark server. '
         'The server responded with status code ${request.status}.'
       );
     }
   }

   /// Reports an error to the benchmark server.
   ///
   /// The server will halt the devicelab task and log the error.
   Future<void> reportError(dynamic error, StackTrace stackTrace) async {
     _checkNotManualMode();
     await html.HttpRequest.request(
       '/on-error',
       method: 'POST',
       mimeType: 'application/json',
       sendData: json.encode(<String, dynamic>{
         'error': '$error',
         'stackTrace': '$stackTrace',
       }),
     );
   }

   /// Reports a message about the demo to the benchmark server.
   Future<void> printToConsole(String report) async {
     _checkNotManualMode();
     await html.HttpRequest.request(
       '/print-to-console',
       method: 'POST',
       mimeType: 'text/plain',
       sendData: report,
     );
   }

   /// This is the same as calling [html.HttpRequest.request] but it doesn't
   /// crash on 404, which we use to detect `flutter run`.
   Future<html.HttpRequest> _requestXhr(
     String url, {
     String method,
     bool withCredentials,
     String responseType,
     String mimeType,
     Map<String, String> requestHeaders,
     dynamic sendData,
   }) {
     final Completer<html.HttpRequest> completer = Completer<html.HttpRequest>();
     final html.HttpRequest xhr = html.HttpRequest();

     method ??= 'GET';
     xhr.open(method, url, async: true);

     if (withCredentials != null) {
       xhr.withCredentials = withCredentials;
     }

     if (responseType != null) {
       xhr.responseType = responseType;
     }

     if (mimeType != null) {
       xhr.overrideMimeType(mimeType);
     }

     if (requestHeaders != null) {
       requestHeaders.forEach((String header, String value) {
         xhr.setRequestHeader(header, value);
       });
     }

     xhr.onLoad.listen((html.ProgressEvent e) {
       completer.complete(xhr);
     });

     xhr.onError.listen(completer.completeError);

     if (sendData != null) {
       xhr.send(sendData);
     } else {
       xhr.send();
     }

     return completer.future;
   }
 }
	// 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 'dart:convert' show json;
	import 'dart:html' as html;
	import 'dart:math' as math;

	import 'package:macrobenchmarks/src/web/bench_text_layout.dart';
	import 'package:macrobenchmarks/src/web/bench_text_out_of_picture_bounds.dart';

	import 'package:gallery/benchmarks/gallery_automator.dart' show DemoType, typeOfDemo;

	import 'src/web/bench_build_image.dart';
	import 'src/web/bench_build_material_checkbox.dart';
	import 'src/web/bench_card_infinite_scroll.dart';
	import 'src/web/bench_child_layers.dart';
	import 'src/web/bench_clipped_out_pictures.dart';
	import 'src/web/bench_draw_rect.dart';
	import 'src/web/bench_dynamic_clip_on_static_picture.dart';
	import 'src/web/bench_mouse_region_grid_hover.dart';
	import 'src/web/bench_mouse_region_grid_scroll.dart';
	import 'src/web/bench_mouse_region_mixed_grid_hover.dart';
	import 'src/web/bench_paths.dart';
	import 'src/web/bench_picture_recording.dart';
	import 'src/web/bench_simple_lazy_text_scroll.dart';
	import 'src/web/bench_text_out_of_picture_bounds.dart';
	import 'src/web/gallery/gallery_recorder.dart';
	import 'src/web/recorder.dart';

	typedef RecorderFactory = Recorder Function();

	const bool isCanvasKit = bool.fromEnvironment('FLUTTER_WEB_USE_SKIA', defaultValue: false);

	const String _galleryBenchmarkPrefix = 'gallery_v2';

	/// List of all benchmarks that run in the devicelab.
	///
	/// When adding a new benchmark, add it to this map. Make sure that the name
	/// of your benchmark is unique.
	final Map<String, RecorderFactory> benchmarks = <String, RecorderFactory>{
	BenchBuildImage.benchmarkName: () => BenchBuildImage(),
	BenchCardInfiniteScroll.benchmarkName: () => BenchCardInfiniteScroll.forward(),
	BenchCardInfiniteScroll.benchmarkNameBackward: () => BenchCardInfiniteScroll.backward(),
	BenchClippedOutPictures.benchmarkName: () => BenchClippedOutPictures(),
	BenchDrawRect.benchmarkName: () => BenchDrawRect.staticPaint(),
	BenchDrawRect.variablePaintBenchmarkName: () => BenchDrawRect.variablePaint(),
	BenchPathRecording.benchmarkName: () => BenchPathRecording(),
	BenchTextOutOfPictureBounds.benchmarkName: () => BenchTextOutOfPictureBounds(),
	BenchSimpleLazyTextScroll.benchmarkName: () => BenchSimpleLazyTextScroll(),
	BenchBuildMaterialCheckbox.benchmarkName: () => BenchBuildMaterialCheckbox(),
	BenchDynamicClipOnStaticPicture.benchmarkName: () => BenchDynamicClipOnStaticPicture(),
	BenchPictureRecording.benchmarkName: () => BenchPictureRecording(),
	BenchUpdateManyChildLayers.benchmarkName: () => BenchUpdateManyChildLayers(),
	BenchMouseRegionGridScroll.benchmarkName: () => BenchMouseRegionGridScroll(),
	BenchMouseRegionGridHover.benchmarkName: () => BenchMouseRegionGridHover(),
	BenchMouseRegionMixedGridHover.benchmarkName: () => BenchMouseRegionMixedGridHover(),
	if (isCanvasKit)
	BenchBuildColorsGrid.canvasKitBenchmarkName: () => BenchBuildColorsGrid.canvasKit(),

	// Benchmarks that we don't want to run using CanvasKit.
	if (!isCanvasKit) ...<String, RecorderFactory>{
	BenchTextLayout.domBenchmarkName: () => BenchTextLayout(useCanvas: false),
	BenchTextLayout.canvasBenchmarkName: () => BenchTextLayout(useCanvas: true),
	BenchTextCachedLayout.domBenchmarkName: () => BenchTextCachedLayout(useCanvas: false),
	BenchTextCachedLayout.canvasBenchmarkName: () => BenchTextCachedLayout(useCanvas: true),
	BenchBuildColorsGrid.domBenchmarkName: () => BenchBuildColorsGrid.dom(),
	BenchBuildColorsGrid.canvasBenchmarkName: () => BenchBuildColorsGrid.canvas(),

	// The following benchmark is for the Flutter Gallery.
	// This benchmark is failing when run with CanvasKit, so we skip it
	// for now.
	// TODO(yjbanov): https://github.com/flutter/flutter/issues/59082
	'${_galleryBenchmarkPrefix}_studies_perf': () => GalleryRecorder(
	benchmarkName: '${_galleryBenchmarkPrefix}_studies_perf',
	shouldRunPredicate: (String demo) => typeOfDemo(demo) == DemoType.study,
	),
	'${_galleryBenchmarkPrefix}_unanimated_perf': () => GalleryRecorder(
	benchmarkName: '${_galleryBenchmarkPrefix}_unanimated_perf',
	shouldRunPredicate: (String demo) => typeOfDemo(demo) == DemoType.unanimatedWidget,
	),
	'${_galleryBenchmarkPrefix}_animated_perf': () => GalleryRecorder(
	benchmarkName: '${_galleryBenchmarkPrefix}_animated_perf',
	shouldRunPredicate: (String demo) => typeOfDemo(demo) == DemoType.animatedWidget,
	),
	'${_galleryBenchmarkPrefix}_scroll_perf': () => GalleryRecorder(
	benchmarkName: '${_galleryBenchmarkPrefix}_scroll_perf',
	testScrollsOnly: true,
	),
	},
	};

	final LocalBenchmarkServerClient _client = LocalBenchmarkServerClient();

	Future<void> main() async {
	// Check if the benchmark server wants us to run a specific benchmark.
	final String nextBenchmark = await _client.requestNextBenchmark();

	if (nextBenchmark == LocalBenchmarkServerClient.kManualFallback) {
	_fallbackToManual('The server did not tell us which benchmark to run next.');
	return;
	}

	await _runBenchmark(nextBenchmark);
	html.window.location.reload();
	}

	Future<void> _runBenchmark(String benchmarkName) async {
	final RecorderFactory recorderFactory = benchmarks[benchmarkName];

	if (recorderFactory == null) {
	_fallbackToManual('Benchmark $benchmarkName not found.');
	return;
	}

	await runZoned<Future<void>>(
	() async {
	final Recorder recorder = recorderFactory();
	final Runner runner = recorder.isTracingEnabled && !_client.isInManualMode
	? Runner(
	recorder: recorder,
	setUpAllDidRun: () => _client.startPerformanceTracing(benchmarkName),
	tearDownAllWillRun: _client.stopPerformanceTracing,
	)
	: Runner(recorder: recorder);

	final Profile profile = await runner.run();
	if (!_client.isInManualMode) {
	await _client.sendProfileData(profile);
	} else {
	_printResultsToScreen(profile);
	print(profile);
	}
	},
	zoneSpecification: ZoneSpecification(
	print: (Zone self, ZoneDelegate parent, Zone zone, String line) async {
	if (_client.isInManualMode) {
	parent.print(zone, '[$benchmarkName] $line');
	} else {
	await _client.printToConsole(line);
	}
	},
	handleUncaughtError: (
	Zone self,
	ZoneDelegate parent,
	Zone zone, Object error,
	StackTrace stackTrace,
	) async {
	if (_client.isInManualMode) {
	parent.print(zone, '[$benchmarkName] $error, $stackTrace');
	parent.handleUncaughtError(zone, error, stackTrace);
	} else {
	await _client.reportError(error, stackTrace);
	}
	},
	),
	);
	}

	void _fallbackToManual(String error) {
	html.document.body.appendHtml('''
	<div id="manual-panel">
	<h3>$error</h3>

	<p>Choose one of the following benchmarks:</p>

	<!-- Absolutely position it so it receives the clicks and not the glasspane -->
	<ul style="position: absolute">
	${
	benchmarks.keys
	.map((String name) => '<li><button id="$name">$name</button></li>')
	.join('\n')
	}
	</ul>
	</div>
	''', validator: html.NodeValidatorBuilder()..allowHtml5()..allowInlineStyles());

	for (final String benchmarkName in benchmarks.keys) {
	final html.Element button = html.document.querySelector('#$benchmarkName');
	button.addEventListener('click', (_) {
	final html.Element manualPanel = html.document.querySelector('#manual-panel');
	manualPanel?.remove();
	_runBenchmark(benchmarkName);
	});
	}
	}

	/// Visualizes results on the Web page for manual inspection.
	void _printResultsToScreen(Profile profile) {
	html.document.body.remove();
	html.document.body = html.BodyElement();
	html.document.body.appendHtml('<h2>${profile.name}</h2>');

	profile.scoreData.forEach((String scoreKey, Timeseries timeseries) {
	html.document.body.appendHtml('<h2>$scoreKey</h2>');
	html.document.body.appendHtml('<pre>${timeseries.computeStats()}</pre>');
	html.document.body.append(TimeseriesVisualization(timeseries).render());
	});
	}

	/// Draws timeseries data and statistics on a canvas.
	class TimeseriesVisualization {
	TimeseriesVisualization(this._timeseries) {
	_stats = _timeseries.computeStats();
	_canvas = html.CanvasElement();
	_screenWidth = html.window.screen.width;
	_canvas.width = _screenWidth;
	_canvas.height = (_kCanvasHeight * html.window.devicePixelRatio).round();
	_canvas.style
	..width = '100%'
	..height = '${_kCanvasHeight}px'
	..outline = '1px solid green';
	_ctx = _canvas.context2D;

	// The amount of vertical space available on the chart. Because some
	// outliers can be huge they can dwarf all the useful values. So we
	// limit it to 1.5 x the biggest non-outlier.
	_maxValueChartRange = 1.5 * _stats.samples
	.where((AnnotatedSample sample) => !sample.isOutlier)
	.map<double>((AnnotatedSample sample) => sample.magnitude)
	.fold<double>(0, math.max);
	}

	static const double _kCanvasHeight = 200;

	final Timeseries _timeseries;
	TimeseriesStats _stats;
	html.CanvasElement _canvas;
	html.CanvasRenderingContext2D _ctx;
	int _screenWidth;

	// Used to normalize benchmark values to chart height.
	double _maxValueChartRange;

	/// Converts a sample value to vertical canvas coordinates.
	///
	/// This does not work for horizontal coordinates.
	double _normalized(double value) {
	return _kCanvasHeight * value / _maxValueChartRange;
	}

	/// A utility for drawing lines.
	void drawLine(num x1, num y1, num x2, num y2) {
	_ctx.beginPath();
	_ctx.moveTo(x1, y1);
	_ctx.lineTo(x2, y2);
	_ctx.stroke();
	}

	/// Renders the timeseries into a `<canvas>` and returns the canvas element.
	html.CanvasElement render() {
	_ctx.translate(0, _kCanvasHeight * html.window.devicePixelRatio);
	_ctx.scale(1, -html.window.devicePixelRatio);

	final double barWidth = _screenWidth / _stats.samples.length;
	double xOffset = 0;
	for (int i = 0; i < _stats.samples.length; i++) {
	final AnnotatedSample sample = _stats.samples[i];

	if (sample.isWarmUpValue) {
	// Put gray background behing warm-up samples.
	_ctx.fillStyle = 'rgba(200,200,200,1)';
	_ctx.fillRect(xOffset, 0, barWidth, _normalized(_maxValueChartRange));
	}

	if (sample.magnitude > _maxValueChartRange) {
	// The sample value is so big it doesn't fit on the chart. Paint it purple.
	_ctx.fillStyle = 'rgba(100,50,100,0.8)';
	} else if (sample.isOutlier) {
	// The sample is an outlier, color it light red.
	_ctx.fillStyle = 'rgba(255,50,50,0.6)';
	} else {
	// A non-outlier sample, color it light blue.
	_ctx.fillStyle = 'rgba(50,50,255,0.6)';
	}

	_ctx.fillRect(xOffset, 0, barWidth - 1, _normalized(sample.magnitude));
	xOffset += barWidth;
	}

	// Draw a horizontal solid line corresponding to the average.
	_ctx.lineWidth = 1;
	drawLine(0, _normalized(_stats.average), _screenWidth, _normalized(_stats.average));

	// Draw a horizontal dashed line corresponding to the outlier cut off.
	_ctx.setLineDash(<num>[5, 5]);
	drawLine(0, _normalized(_stats.outlierCutOff), _screenWidth, _normalized(_stats.outlierCutOff));

	// Draw a light red band that shows the noise (1 stddev in each direction).
	_ctx.fillStyle = 'rgba(255,50,50,0.3)';
	_ctx.fillRect(
	0,
	_normalized(_stats.average * (1 - _stats.noise)),
	_screenWidth,
	_normalized(2 * _stats.average * _stats.noise),
	);

	return _canvas;
	}
	}

	/// Implements the client REST API for the local benchmark server.
	///
	/// The local server is optional. If it is not available the benchmark UI must
	/// implement a manual fallback. This allows debugging benchmarks using plain
	/// `flutter run`.
	class LocalBenchmarkServerClient {
	/// This value is returned by [requestNextBenchmark].
	static const String kManualFallback = '__manual_fallback__';

	/// Whether we fell back to manual mode.
	///
	/// This happens when you run benchmarks using plain `flutter run` rather than
	/// devicelab test harness. The test harness spins up a special server that
	/// provides API for automatically picking the next benchmark to run.
	bool isInManualMode;

	/// Asks the local server for the name of the next benchmark to run.
	///
	/// Returns [kManualFallback] if local server is not available (uses 404 as a
	/// signal).
	Future<String> requestNextBenchmark() async {
	final html.HttpRequest request = await _requestXhr(
	'/next-benchmark',
	method: 'POST',
	mimeType: 'application/json',
	sendData: json.encode(benchmarks.keys.toList()),
	);

	// 404 is expected in the following cases:
	// - The benchmark is ran using plain `flutter run`, which does not provide "next-benchmark" handler.
	// - We ran all benchmarks and the benchmark is telling us there are no more benchmarks to run.
	if (request.status == 404) {
	isInManualMode = true;
	return kManualFallback;
	}

	isInManualMode = false;
	return request.responseText;
	}

	void _checkNotManualMode() {
	if (isInManualMode) {
	throw StateError('Operation not supported in manual fallback mode.');
	}
	}

	/// Asks the local server to begin tracing performance.
	///
	/// This uses the chrome://tracing tracer, which is not available from within
	/// the page itself, and therefore must be controlled from outside using the
	/// DevTools Protocol.
	Future<void> startPerformanceTracing(String benchmarkName) async {
	_checkNotManualMode();
	await html.HttpRequest.request(
	'/start-performance-tracing?label=$benchmarkName',
	method: 'POST',
	mimeType: 'application/json',
	);
	}

	/// Stops the performance tracing session started by [startPerformanceTracing].
	Future<void> stopPerformanceTracing() async {
	_checkNotManualMode();
	await html.HttpRequest.request(
	'/stop-performance-tracing',
	method: 'POST',
	mimeType: 'application/json',
	);
	}

	/// Sends the profile data collected by the benchmark to the local benchmark
	/// server.
	Future<void> sendProfileData(Profile profile) async {
	_checkNotManualMode();
	final html.HttpRequest request = await html.HttpRequest.request(
	'/profile-data',
	method: 'POST',
	mimeType: 'application/json',
	sendData: json.encode(profile.toJson()),
	);
	if (request.status != 200) {
	throw Exception(
	'Failed to report profile data to benchmark server. '
	'The server responded with status code ${request.status}.'
	);
	}
	}

	/// Reports an error to the benchmark server.
	///
	/// The server will halt the devicelab task and log the error.
	Future<void> reportError(dynamic error, StackTrace stackTrace) async {
	_checkNotManualMode();
	await html.HttpRequest.request(
	'/on-error',
	method: 'POST',
	mimeType: 'application/json',
	sendData: json.encode(<String, dynamic>{
	'error': '$error',
	'stackTrace': '$stackTrace',
	}),
	);
	}

	/// Reports a message about the demo to the benchmark server.
	Future<void> printToConsole(String report) async {
	_checkNotManualMode();
	await html.HttpRequest.request(
	'/print-to-console',
	method: 'POST',
	mimeType: 'text/plain',
	sendData: report,
	);
	}

	/// This is the same as calling [html.HttpRequest.request] but it doesn't
	/// crash on 404, which we use to detect `flutter run`.
	Future<html.HttpRequest> _requestXhr(
	String url, {
	String method,
	bool withCredentials,
	String responseType,
	String mimeType,
	Map<String, String> requestHeaders,
	dynamic sendData,
	}) {
	final Completer<html.HttpRequest> completer = Completer<html.HttpRequest>();
	final html.HttpRequest xhr = html.HttpRequest();

	method ??= 'GET';
	xhr.open(method, url, async: true);

	if (withCredentials != null) {
	xhr.withCredentials = withCredentials;
	}

	if (responseType != null) {
	xhr.responseType = responseType;
	}

	if (mimeType != null) {
	xhr.overrideMimeType(mimeType);
	}

	if (requestHeaders != null) {
	requestHeaders.forEach((String header, String value) {
	xhr.setRequestHeader(header, value);
	});
	}

	xhr.onLoad.listen((html.ProgressEvent e) {
	completer.complete(xhr);
	});

	xhr.onError.listen(completer.completeError);

	if (sendData != null) {
	xhr.send(sendData);
	} else {
	xhr.send();
	}

	return completer.future;
	}
	}