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[web] Introduce js interop to enable experimental flags on web #17099
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| Original file line number | Diff line number | Diff line change |
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| @@ -0,0 +1,53 @@ | ||
| // Copyright 2013 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. | ||
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| // @dart = 2.6 | ||
| part of engine; | ||
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| /// A bag of all experiment flags in the web engine. | ||
| /// | ||
| /// This class also handles platform messages that can be sent to enable/disable | ||
| /// certain experiments at runtime without the need to access engine internals. | ||
| class WebExperiments { | ||
| WebExperiments._() { | ||
| js.context['_flutter_internal_update_experiment'] = updateExperiment; | ||
| registerHotRestartListener(() { | ||
| js.context['_flutter_internal_update_experiment'] = null; | ||
| }); | ||
| } | ||
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| static WebExperiments ensureInitialized() { | ||
| if (WebExperiments.instance == null) { | ||
| WebExperiments.instance = WebExperiments._(); | ||
| } | ||
| return WebExperiments.instance; | ||
| } | ||
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| static WebExperiments instance; | ||
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| /// Experiment flag for using canvas-based text measurement. | ||
| bool get useCanvasText => _useCanvasText ?? false; | ||
|
Contributor
There was a problem hiding this comment. Does allowing
Contributor
Author
There was a problem hiding this comment. Yes. In tests, we set the flag to a specific value (true or false), then we set it back to |
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| set useCanvasText(bool enabled) { | ||
| _useCanvasText = enabled; | ||
| } | ||
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| bool _useCanvasText = const bool.fromEnvironment( | ||
| 'FLUTTER_WEB_USE_EXPERIMENTAL_CANVAS_TEXT', | ||
| defaultValue: null, | ||
| ); | ||
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| /// Reset all experimental flags to their default values. | ||
| void reset() { | ||
| _useCanvasText = null; | ||
| } | ||
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| /// Used to enable/disable experimental flags in the web engine. | ||
| void updateExperiment(String name, bool enabled) { | ||
| switch (name) { | ||
| case 'useCanvasText': | ||
| _useCanvasText = enabled; | ||
| break; | ||
| } | ||
| } | ||
| } | ||
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,80 @@ | ||
| // Copyright 2013 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. | ||
|
|
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| // @dart = 2.6 | ||
| import 'dart:html' as html; | ||
| import 'dart:js_util' as js_util; | ||
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| import 'package:test/test.dart'; | ||
| import 'package:ui/src/engine.dart'; | ||
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| void main() { | ||
| setUp(() { | ||
| WebExperiments.ensureInitialized(); | ||
| }); | ||
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| tearDown(() { | ||
| WebExperiments.instance.reset(); | ||
| }); | ||
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| test('default web experiment values', () { | ||
| expect(WebExperiments.instance.useCanvasText, false); | ||
| }); | ||
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| test('can turn on/off web experiments', () { | ||
| WebExperiments.instance.updateExperiment('useCanvasText', true); | ||
| expect(WebExperiments.instance.useCanvasText, true); | ||
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| WebExperiments.instance.updateExperiment('useCanvasText', false); | ||
| expect(WebExperiments.instance.useCanvasText, false); | ||
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| WebExperiments.instance.updateExperiment('useCanvasText', null); | ||
| // Goes back to default value. | ||
| expect(WebExperiments.instance.useCanvasText, false); | ||
| }); | ||
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| test('ignores unknown experiments', () { | ||
| expect(WebExperiments.instance.useCanvasText, false); | ||
| WebExperiments.instance.updateExperiment('foobarbazqux', true); | ||
| expect(WebExperiments.instance.useCanvasText, false); | ||
| WebExperiments.instance.updateExperiment('foobarbazqux', false); | ||
| expect(WebExperiments.instance.useCanvasText, false); | ||
| }); | ||
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| test('can reset web experiments', () { | ||
| WebExperiments.instance.updateExperiment('useCanvasText', true); | ||
| WebExperiments.instance.reset(); | ||
| expect(WebExperiments.instance.useCanvasText, false); | ||
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| WebExperiments.instance.updateExperiment('useCanvasText', true); | ||
| WebExperiments.instance.updateExperiment('foobarbazqux', true); | ||
| WebExperiments.instance.reset(); | ||
| expect(WebExperiments.instance.useCanvasText, false); | ||
| }); | ||
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| test('js interop also works', () { | ||
| expect(WebExperiments.instance.useCanvasText, false); | ||
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| expect(() => jsUpdateExperiment('useCanvasText', true), returnsNormally); | ||
| expect(WebExperiments.instance.useCanvasText, true); | ||
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| expect(() => jsUpdateExperiment('useCanvasText', null), returnsNormally); | ||
| expect(WebExperiments.instance.useCanvasText, false); | ||
| }); | ||
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| test('js interop throws on wrong type', () { | ||
| expect(() => jsUpdateExperiment(123, true), throwsA(anything)); | ||
| expect(() => jsUpdateExperiment('foo', 123), throwsA(anything)); | ||
| expect(() => jsUpdateExperiment('foo', 'bar'), throwsA(anything)); | ||
| expect(() => jsUpdateExperiment(false, 'foo'), throwsA(anything)); | ||
| }); | ||
| } | ||
|
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| void jsUpdateExperiment(dynamic name, dynamic enabled) { | ||
| js_util.callMethod( | ||
| html.window, | ||
| '_flutter_internal_update_experiment', | ||
| <dynamic>[name, enabled], | ||
| ); | ||
| } |
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I'm surprised this works without
jsifyorallowInteropor some such 🤔