[CP-beta][Win32] FlutterDesktopEngineGetGraphicsAdapter should use out parameter#185634
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…er (flutter#185590) The returned `IDXGIAdapter` is owned by caller, which is not obvious from the original signature. Usual pattern in COM is to use out parameters with smart pointers: ```cpp ComPtr<IDXGIAdapter> ptr; FlutterDesktopEngineGetGraphicsAdapter(engine, ptr.GetAddressOf()); ``` With the old signature it's easy to leak the `IDXGIAdapter` ```cpp ComPtr<IDXGIAdapter> ptr; // This retains the adapter instead of taking ownership ptr = FlutterDesktopEngineGetGraphicsAdapter(engine); ``` ## Pre-launch Checklist - [x] I read the [Contributor Guide] and followed the process outlined there for submitting PRs. - [x] I read the [AI contribution guidelines] and understand my responsibilities, or I am not using AI tools. - [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. - [x] 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]. If this change needs to override an active code freeze, provide a comment explaining why. The code freeze workflow can be overridden by code reviewers. See pinned issues for any active code freezes with guidance. **Note**: The Flutter team is currently trialing the use of [Gemini Code Assist for GitHub](https://developers.google.com/gemini-code-assist/docs/review-github-code). Comments from the `gemini-code-assist` bot should not be taken as authoritative feedback from the Flutter team. If you find its comments useful you can update your code accordingly, but if you are unsure or disagree with the feedback, please feel free to wait for a Flutter team member's review for guidance on which automated comments should be addressed. <!-- Links --> [Contributor Guide]: https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md#overview [AI contribution guidelines]: https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md#ai-contribution-guidelines [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
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@loic-sharma please fill out the PR description above, afterwards the release team will review this request. |
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This pull request was opened from and to a release candidate branch. This should only be done as part of the official Flutter release process. If you are attempting to make a regular contribution to the Flutter project, please close this PR and follow the instructions at Tree Hygiene for detailed instructions on contributing to Flutter. Reviewers: Use caution before merging pull requests to release branches. Ensure the proper procedure has been followed. |
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This pull request refactors the Windows graphics adapter retrieval API to use an out-parameter pattern across the engine and its client wrappers. Feedback identifies that IDXGIAdapter is a COM object and requires smart pointer management in unit tests to avoid memory leaks. Suggestions also include adding defensive null checks for out-parameters and adopting more idiomatic COM resource management in the implementation.
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@knopp Please fill out the details on this cherrypick PR. I'll be the approver :) |
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This pull request is created by automatic cherry pick workflow
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Impact Description:
Flutter 3.44 will introduce a new C++ API on Windows to get the engine's current DirectX adapter. However, the new API is prone to leaks:
// This leaks as it retains the adapter instead of taking ownership. ComPtr<IDXGIAdapter> ptr; ptr = FlutterDesktopEngineGetGraphicsAdapter(engine);The cherrypick updates the new API to instead use an out parameter, which is customary for COM APIs and much less prone to memory leaks than returning it from function:
Note
Our ability to make breaking changes to Flutter Windows's C++ API is limited. Cherrypicking this API change lets us correct a bad API before it is shipped. If this cherrypick is rejected, we will be stuck with this leak-prone API for the foreseeable future.
Changelog Description:
[flutter/185639] Improve Flutter Windows's API to get the engine's DirectX adapter
Workaround:
Users can workaround this issue using
ComPtr::Attach:// Attach takes ownership of the pointer returned by the function ComPtr<IDXGIAdapter> ptr; ptr.Attach(FlutterDesktopEngineGetGraphicsAdapter(engine));However, this is not idiomatic. Users are unlikely to figure this out.
Risk:
What is the risk level of this cherry-pick?
Test Coverage:
Are you confident that your fix is well-tested by automated tests?
Validation Steps:
Verified by unit tests.