| // 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:typed_data'; |
| import 'dart:ui' show window; |
| |
| import 'package:flutter_test/flutter_test.dart'; |
| import 'package:flutter/services.dart'; |
| import 'package:flutter/widgets.dart'; |
| |
| void main() { |
| test('Instantiating WidgetsFlutterBinding does neither schedule a frame nor register frame callbacks', () async { |
| // Regression test for https://github.com/flutter/flutter/issues/39494. |
| |
| // Preconditions. |
| expect(WidgetsBinding.instance, isNull); |
| expect(window.onBeginFrame, isNull); |
| expect(window.onDrawFrame, isNull); |
| |
| // Instantiation does nothing with regards to frame scheduling. |
| final WidgetsFlutterBinding binding = WidgetsFlutterBinding.ensureInitialized() as WidgetsFlutterBinding; |
| expect(binding.hasScheduledFrame, isFalse); |
| expect(window.onBeginFrame, isNull); |
| expect(window.onDrawFrame, isNull); |
| |
| // Framework starts with detached statue. Sends resumed signal to enable frame. |
| final ByteData message = const StringCodec().encodeMessage('AppLifecycleState.resumed'); |
| await ServicesBinding.instance.defaultBinaryMessenger.handlePlatformMessage('flutter/lifecycle', message, (_) { }); |
| |
| // A frame can only be scheduled when there is a root widget. |
| binding.attachRootWidget(const Placeholder()); |
| |
| // Frame callbacks are registered lazily when a frame is scheduled. |
| binding.scheduleFrame(); |
| expect(window.onBeginFrame, isNotNull); |
| expect(window.onDrawFrame, isNotNull); |
| }); |
| } |