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Reopened from https://github.com/flutter/engine/pull/56501. Fixes [#158450](https://github.com/flutter/flutter/issues/158450). As mentioned in [#158450](https://github.com/flutter/flutter/issues/158450), the crash occurs because a destroyed object may be accessed if the window and view have already been destroyed by the time `KeyEventCallback` is called. This issue is not limited to the `Alt+F4` system key; it may also occur if the window is closed using other key presses, such as pressing `Enter` after navigating to a dialog's "Close" button. This PR proposes a fix that checks whether the view ID is still valid when the callback is invoked. If the view is invalid, the event is skipped for that view. A unit test has been added to assert that the `KeyEventCallback` is invoked when the associated view is valid and not invoked when the view is destroyed. ## Pre-launch Checklist - [x] I read the [Contributor Guide] and followed the process outlined there for submitting PRs. - [x] I read the [Tree Hygiene] wiki page, which explains my responsibilities. - [x] I read and followed the [Flutter Style Guide], including [Features we expect every widget to implement]. - [x] I signed the [CLA]. - [x] I listed at least one issue that this PR fixes in the description above. - [ ] I updated/added relevant documentation (doc comments with `///`). - [x] I added new tests to check the change I am making, or this PR is [test-exempt]. - [x] I followed the [breaking change policy] and added [Data Driven Fixes] where supported. - [x] All existing and new tests are passing. If you need help, consider asking for advice on the #hackers-new channel on [Discord]. <!-- Links --> [Contributor Guide]: https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md#overview [Tree Hygiene]: https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md [test-exempt]: https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md#tests [Flutter Style Guide]: https://github.com/flutter/flutter/blob/main/docs/contributing/Style-guide-for-Flutter-repo.md [Features we expect every widget to implement]: https://github.com/flutter/flutter/blob/main/docs/contributing/Style-guide-for-Flutter-repo.md#features-we-expect-every-widget-to-implement [CLA]: https://cla.developers.google.com/ [flutter/tests]: https://github.com/flutter/tests [breaking change policy]: https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md#handling-breaking-changes [Discord]: https://github.com/flutter/flutter/blob/main/docs/contributing/Chat.md [Data Driven Fixes]: https://github.com/flutter/flutter/blob/main/docs/contributing/Data-driven-Fixes.md
Windows Platform Embedder
This code is the glue between the Flutter engine and the Windows platform. It is responsible for:
- Launching the Flutter engine.
- Providing a view for the Flutter engine to render into.
- Dispatching events to the Flutter engine.
For more information on embedders, see the Flutter architectural overview.
Caution
This is a best effort attempt to document the Windows embedder. It is not guaranteed to be up to date or complete. If you find a discrepancy, please send a pull request!
See also:
- Flutter tool's Windows logic - Builds and runs Flutter Windows apps on the command line.
- Windows app template - The entrypoint for Flutter Windows app. This launches the Windows embedder.
platform-windowsGitHub issues label#hackers-desktopDiscord channel
Developing
See:
- Setting up the Engine development environment
- Compiling for Windows
- Debugging Windows builds with Visual Studio
Notable files
Some notable files include:
flutter_windows_engine.h- Connects the Windows embedder to the Flutter engine.flutter_windows_view.h- The logic for a Flutter view.flutter_window.h- Integrates a Flutter view with Windows (using a win32 child window).//shell/platform/embedder/embedder.h- The API boundary between the Windows embedder and the Flutter engine.