// 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, (_) { }); // Frame callbacks are registered lazily when a frame is scheduled. binding.scheduleFrame(); expect(window.onBeginFrame, isNotNull); expect(window.onDrawFrame, isNotNull); }); }