Adds windows project switch for enabling impeller#188044
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This pull request enables programmatically configuring the Impeller rendering backend on Windows via the project configuration, updating DartProject, FlutterProjectBundle, and FlutterWindowsEngine to support and forward the enable_impeller flag. Feedback suggests optimizing the devicelab test by storing and restoring the original main.cpp content in memory rather than spawning an external git process, and marking the unmodified switches reference as const in flutter_windows_engine.cc to align with the C++ style guide.
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| final Directory appDir = dir(path.join(flutterDirectory.path, 'examples/hello_world')); | ||
| final String mainCppPath = path.join(appDir.path, 'windows', 'runner', 'main.cpp'); | ||
| final mainCppFile = File(mainCppPath); |
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To avoid spawning an external git process to restore the file, we can store the original content in a variable and write it back in the finally block. Let's declare a variable to hold the original content here.
Suggested change
| final mainCppFile = File(mainCppPath); | |
| final mainCppFile = File(mainCppPath); | |
| String? originalMainCppContent; |
| if (!sawImpellerBackendMessage) { | ||
| res = TaskResult.failure( | ||
| 'Did not see "Using the Impeller rendering backend (OpenGLESSDF)." in output', | ||
| final String originalContent = mainCppFile.readAsStringSync(); |
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Store the original content in the originalMainCppContent variable so it can be restored in the finally block.
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| final String originalContent = mainCppFile.readAsStringSync(); | |
| final String originalContent = mainCppFile.readAsStringSync(); | |
| originalMainCppContent = originalContent; |
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| if (mainCppFile.existsSync()) { | ||
| await exec('git', <String>['checkout', mainCppPath]); | ||
| } |
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Restore the original content of main.cpp directly by writing the saved string back to the file. This is faster and more reliable than spawning a git checkout process.
Suggested change
| if (mainCppFile.existsSync()) { | |
| await exec('git', <String>['checkout', mainCppPath]); | |
| } | |
| if (originalMainCppContent != null && mainCppFile.existsSync()) { | |
| mainCppFile.writeAsStringSync(originalMainCppContent); | |
| } |
| auto& switches = project_->GetSwitches(); | ||
| enable_impeller_ = std::find(switches.begin(), switches.end(), | ||
| "--enable-impeller=true") != switches.end(); | ||
| bool enable_impeller = project_->enable_impeller(); |
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According to the Google C++ Style Guide, local reference variables that are not modified should be marked const. Although switches is defined on line 196 (which is outside the modified lines), it should ideally be const auto& switches to ensure const-correctness.
References
- Use constness whenever it makes sense. In particular, use const for parameters and local variables that are not modified. (link)
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Just FYI, for merged threads, @knopp took an enum approach with three values: "default", "merge threads", "split threads": I believe the benefit of this approach was minimizing the migration for folks that are using the C API directly. I don't feel strongly about this, but just bubbling this up for your awareness. |
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Author
I'd like to know more about this. I imagine this is because in the c api you are forced to explicitly list the thread policy in a struct, so there is no concept of a default value? |
Member
Yup exactly. |
Member
Author
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@loic-sharma okay, I switched everything to a ternary enum now. |
Contributor
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autosubmit label was removed for flutter/flutter/188044, because - The status or check suite Google testing has failed. Please fix the issues identified (or deflake) before re-applying this label. |
This was referenced Jun 18, 2026
This was referenced Jun 18, 2026
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flutter/flutter@b10d0f1...15963bc 2026-06-18 engine-flutter-autoroll@skia.org Roll Skia from 6e84902d56c3 to 1ae2466c9ea5 (4 revisions) (flutter/flutter#188172) 2026-06-18 engine-flutter-autoroll@skia.org Roll Packages from 6ce00a8 to 4fd05e6 (3 revisions) (flutter/flutter#188171) 2026-06-18 robert.ancell@canonical.com [Linux] Fix vertical offset in composite_layer (flutter/flutter#188145) 2026-06-18 robert.ancell@canonical.com [Linux] Fix incorrect GL datatypes for uniform locations (flutter/flutter#188143) 2026-06-18 engine-flutter-autoroll@skia.org Roll Dart SDK from e05c69222ea4 to 5883736e7670 (2 revisions) (flutter/flutter#188168) 2026-06-18 engine-flutter-autoroll@skia.org Roll Skia from 046277850e8d to 6e84902d56c3 (5 revisions) (flutter/flutter#188165) 2026-06-18 engine-flutter-autoroll@skia.org Roll Fuchsia Linux SDK from or21OEdGtairm6nl9... to 1E2qOlNnC2Ucn-1oV... (flutter/flutter#188162) 2026-06-18 engine-flutter-autoroll@skia.org Roll Skia from 8dd207d443d3 to 046277850e8d (1 revision) (flutter/flutter#188153) 2026-06-18 31859944+LongCatIsLooong@users.noreply.github.com Add entitlements.txt entries for new dart sdk binaries (flutter/flutter#188133) 2026-06-18 engine-flutter-autoroll@skia.org Roll Dart SDK from b670723c5f07 to e05c69222ea4 (1 revision) (flutter/flutter#188146) 2026-06-18 robert.ancell@canonical.com Fix bounds checking in FlAccessibleTextField (flutter/flutter#188137) 2026-06-18 engine-flutter-autoroll@skia.org Roll Skia from f5a2921fe23e to 8dd207d443d3 (2 revisions) (flutter/flutter#188141) 2026-06-18 30870216+gaaclarke@users.noreply.github.com Adds tests for disabling macos impeller (flutter/flutter#188132) 2026-06-17 jlemanski1@gmail.com Improve Flutter Web accessibility: update flt meta viewport tag to align with WCAG 2 guidelines (flutter/flutter#182047) 2026-06-17 engine-flutter-autoroll@skia.org Roll Dart SDK from e39bde5b1bfc to b670723c5f07 (2 revisions) (flutter/flutter#188130) 2026-06-17 engine-flutter-autoroll@skia.org Roll Skia from 066bfbac7282 to f5a2921fe23e (1 revision) (flutter/flutter#188128) 2026-06-17 matt.boetger@gmail.com Support --trace-systrace in release builds on Android (flutter/flutter#186359) 2026-06-17 matt.boetger@gmail.com Isolate compiled dill caches by TargetModel (flutter/flutter#187253) 2026-06-17 98614782+auto-submit[bot]@users.noreply.github.com Reverts "refactor(web): Unify Image on Skwasm and CanvasKit (#187873)" (flutter/flutter#188124) 2026-06-17 matt.kosarek@canonical.com Use a mock EGL manager in windows unittests to avoid flaky rendering calls (flutter/flutter#188078) 2026-06-17 matt.boetger@gmail.com [Android] Remove support for unused manifest flags (flutter/flutter#186021) 2026-06-17 30870216+gaaclarke@users.noreply.github.com Adds windows project switch for enabling impeller (flutter/flutter#188044) 2026-06-17 15619084+vashworth@users.noreply.github.com Skip prefetch SwiftPM dependencies if the project hasn't been migrated to SwiftPM yet (flutter/flutter#187206) 2026-06-17 nshahan@google.com [flutter_tools] Bump dwds to 27.1.2 (flutter/flutter#187951) 2026-06-17 30870216+gaaclarke@users.noreply.github.com Adds external texture devicelab test for windows impeller (flutter/flutter#187886) 2026-06-17 engine-flutter-autoroll@skia.org Roll Skia from 5d19002eb73e to 066bfbac7282 (2 revisions) (flutter/flutter#188118) 2026-06-17 34871572+gmackall@users.noreply.github.com Add note about magnifier issue when using transparent HCPP pv (flutter/flutter#187753) 2026-06-17 30870216+gaaclarke@users.noreply.github.com [linux]: fixes crash when resizing windows (flutter/flutter#187626) 2026-06-17 56400880+adilburaksen@users.noreply.github.com [flutter_tools] Enforce that package-declared asset paths stay within the package (flutter/flutter#187661) 2026-06-17 jason-simmons@users.noreply.github.com Remove canvaskit_cipd_instance from DEPS (flutter/flutter#188073) If this roll has caused a breakage, revert this CL and stop the roller using the controls here: https://autoroll.skia.org/r/flutter-packages Please CC bmparr@google.com,stuartmorgan@google.com on the revert to ensure that a human is aware of the problem. To file a bug in Packages: https://github.com/flutter/flutter/issues/new/choose To report a problem with the AutoRoller itself, please file a bug: https://issues.skia.org/issues/new?component=1389291&template=1850622 Documentation for the AutoRoller is here: https://skia.googlesource.com/buildbot/+doc/main/autoroll/README.md
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fixes flutter#187736 ## 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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fixes flutter#187736 ## 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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fixes #187736
Pre-launch Checklist
///).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. Comments from the
gemini-code-assistbot 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.