// 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/scheduler.dart'; import 'package:flutter/services.dart'; import 'package:flutter/widgets.dart'; import 'package:flutter_test/flutter_test.dart'; void main() { test('Can only schedule frames after widget binding attaches the root widget', () async { final WidgetsBinding binding = WidgetsFlutterBinding.ensureInitialized(); expect(SchedulerBinding.instance!.framesEnabled, isFalse); expect(SchedulerBinding.instance!.hasScheduledFrame, isFalse); // Sends a message to notify that the engine is ready to accept frames. final ByteData message = const StringCodec().encodeMessage('AppLifecycleState.resumed')!; await ServicesBinding.instance!.defaultBinaryMessenger.handlePlatformMessage('flutter/lifecycle', message, (_) { }); // Enables the semantics should not schedule any frames if the root widget // has not been attached. binding.setSemanticsEnabled(true); expect(SchedulerBinding.instance!.framesEnabled, isFalse); expect(SchedulerBinding.instance!.hasScheduledFrame, isFalse); // The widget binding should be ready to produce frames after it attaches // the root widget. binding.attachRootWidget(const Placeholder()); expect(SchedulerBinding.instance!.framesEnabled, isTrue); expect(SchedulerBinding.instance!.hasScheduledFrame, isTrue); }); }