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## Background
The Windows runner has a race at startup:
1. **Platform thread**: creates a hidden window
2. **Platform thread**: launches the Flutter engine
3. **UI/Raster threads**: renders the first frame
4. **Platform thread**: Registers a callback to show the window once the next frame has been rendered.
Steps 3 and 4 happen in parallel and it is possible for step 3 to complete before step 4 starts. In this scenario, the next frame callback is never called and the window is never shown.
As a result the `windows_startup_test`'s test, which [verifies that the "show window" callback is called](1f09a8662d/dev/integration_tests/windows_startup_test/windows/runner/flutter_window.cpp (L60-L64)
), can flake if the first frame is rendered before the show window callback has been registered.
## Solution
This change makes the runner schedule a frame after it registers the next frame callback. If step 3 hasn't completed yet, this no-ops as a frame is already scheduled. If step 3 has already completed, a new frame will be rendered, which will call the next frame callback and show the window.
Part of https://github.com/flutter/flutter/issues/119415
See this thread for alternatives that were considered: https://github.com/flutter/engine/pull/42061#issuecomment-1550080722
145 lines
5.0 KiB
Dart
145 lines
5.0 KiB
Dart
// Copyright 2014 The Flutter Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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import 'base/file_system.dart';
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import 'base/utils.dart';
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import 'platform_plugins.dart';
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import 'project.dart';
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/// Represents a CMake-based sub-project.
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///
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/// This defines interfaces common to Windows and Linux projects.
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abstract class CmakeBasedProject {
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/// The parent of this project.
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FlutterProject get parent;
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/// Whether the subproject (either Windows or Linux) exists in the Flutter project.
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bool existsSync();
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/// The native project CMake specification.
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File get cmakeFile;
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/// Contains definitions for the Flutter library and the tool.
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File get managedCmakeFile;
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/// Contains definitions for FLUTTER_ROOT, LOCAL_ENGINE, and more flags for
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/// the build.
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File get generatedCmakeConfigFile;
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/// Included CMake with rules and variables for plugin builds.
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File get generatedPluginCmakeFile;
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/// The directory to write plugin symlinks.
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Directory get pluginSymlinkDirectory;
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}
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/// The Windows sub project.
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class WindowsProject extends FlutterProjectPlatform implements CmakeBasedProject {
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WindowsProject.fromFlutter(this.parent);
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@override
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final FlutterProject parent;
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@override
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String get pluginConfigKey => WindowsPlugin.kConfigKey;
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String get _childDirectory => 'windows';
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@override
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bool existsSync() => _editableDirectory.existsSync() && cmakeFile.existsSync();
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@override
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File get cmakeFile => _editableDirectory.childFile('CMakeLists.txt');
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@override
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File get managedCmakeFile => managedDirectory.childFile('CMakeLists.txt');
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@override
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File get generatedCmakeConfigFile => ephemeralDirectory.childFile('generated_config.cmake');
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@override
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File get generatedPluginCmakeFile => managedDirectory.childFile('generated_plugins.cmake');
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/// The native entrypoint's CMake specification.
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File get runnerCmakeFile => runnerDirectory.childFile('CMakeLists.txt');
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/// The native entrypoint's file that adds Flutter to the window.
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File get runnerFlutterWindowFile => runnerDirectory.childFile('flutter_window.cpp');
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/// The native entrypoint's resource file. Used to configure things
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/// like the application icon, name, and version.
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File get runnerResourceFile => runnerDirectory.childFile('Runner.rc');
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@override
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Directory get pluginSymlinkDirectory => ephemeralDirectory.childDirectory('.plugin_symlinks');
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Directory get _editableDirectory => parent.directory.childDirectory(_childDirectory);
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/// The directory in the project that is managed by Flutter. As much as
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/// possible, files that are edited by Flutter tooling after initial project
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/// creation should live here.
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Directory get managedDirectory => _editableDirectory.childDirectory('flutter');
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/// The subdirectory of [managedDirectory] that contains files that are
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/// generated on the fly. All generated files that are not intended to be
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/// checked in should live here.
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Directory get ephemeralDirectory => managedDirectory.childDirectory('ephemeral');
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/// The directory in the project that is owned by the app. As much as
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/// possible, Flutter tooling should not edit files in this directory after
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/// initial project creation.
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Directory get runnerDirectory => _editableDirectory.childDirectory('runner');
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Future<void> ensureReadyForPlatformSpecificTooling() async {}
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}
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/// The Linux sub project.
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class LinuxProject extends FlutterProjectPlatform implements CmakeBasedProject {
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LinuxProject.fromFlutter(this.parent);
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@override
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final FlutterProject parent;
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@override
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String get pluginConfigKey => LinuxPlugin.kConfigKey;
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static final RegExp _applicationIdPattern = RegExp(r'''^\s*set\s*\(\s*APPLICATION_ID\s*"(.*)"\s*\)\s*$''');
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Directory get _editableDirectory => parent.directory.childDirectory('linux');
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/// The directory in the project that is managed by Flutter. As much as
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/// possible, files that are edited by Flutter tooling after initial project
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/// creation should live here.
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Directory get managedDirectory => _editableDirectory.childDirectory('flutter');
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/// The subdirectory of [managedDirectory] that contains files that are
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/// generated on the fly. All generated files that are not intended to be
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/// checked in should live here.
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Directory get ephemeralDirectory => managedDirectory.childDirectory('ephemeral');
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@override
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bool existsSync() => _editableDirectory.existsSync();
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@override
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File get cmakeFile => _editableDirectory.childFile('CMakeLists.txt');
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@override
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File get managedCmakeFile => managedDirectory.childFile('CMakeLists.txt');
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@override
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File get generatedCmakeConfigFile => ephemeralDirectory.childFile('generated_config.cmake');
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@override
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File get generatedPluginCmakeFile => managedDirectory.childFile('generated_plugins.cmake');
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@override
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Directory get pluginSymlinkDirectory => ephemeralDirectory.childDirectory('.plugin_symlinks');
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Future<void> ensureReadyForPlatformSpecificTooling() async {}
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String? get applicationId {
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return firstMatchInFile(cmakeFile, _applicationIdPattern)?.group(1);
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}
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}
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