[Flutter GPU] Inject per-backend defines into shader bundle compilation#187081
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auto-submit[bot] merged 5 commits intoMay 27, 2026
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This pull request introduces platform-discriminating preprocessor defines (such as IMPELLER_TARGET_METAL) during the compilation of bundled shaders, allowing them to specialize per backend. It adds the helper function ShaderBundleTargetPlatformDefines to map target platforms to their respective defines, integrates these defines into the compilation options, and adds corresponding unit tests. The review feedback suggests optimizing performance by returning std::string_view instead of std::string to avoid heap allocations, and ensuring correctness by explicitly setting the target platform on both the backend and reflector options.
gaaclarke
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May 26, 2026
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Mostly looks good. I just have questions about what we want to do about opengles vs opengl.
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| case TargetPlatform::kOpenGLDesktop: | ||
| return {"IMPELLER_TARGET_OPENGLES"}; |
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I don't think we want to conflate opengl and opengles.
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Done. Split into separate defines.
| /// that Impeller's own shaders receive from the build templates. | ||
| /// | ||
| /// @note Exposed only for testing purposes. | ||
| std::vector<std::string_view> ShaderBundleTargetPlatformDefines( |
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Can you add a verb to this function name, please?
- kOpenGLDesktop now emits IMPELLER_TARGET_OPENGL instead of sharing IMPELLER_TARGET_OPENGLES with kOpenGLES. - Rename ShaderBundleTargetPlatformDefines to GetShaderBundleTargetPlatformDefines.
gaaclarke
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lgtm, this is timely for me, thanks
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@gaaclarke Using Flutter GPU for something? :) |
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Oh no, I was working on text rendering on linux. Because we use coretext on macos and freetype on linux there is some differences in the fragment shader I had to make to correct gamma. I wish I had free time right now to play around with stuff. |
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autosubmit label was removed for flutter/flutter/187081, because - The status or check suite Mac build_android_host_app_with_module_aar has failed. Please fix the issues identified (or deflake) before re-applying this label. |
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flutter/flutter@c8f2f16...e70534d 2026-05-28 30870216+gaaclarke@users.noreply.github.com Linux glyph gamma correction (flutter/flutter#187122) 2026-05-28 chris@bracken.jp [iOS] Eliminate strong retain cycle from VSyncClient (flutter/flutter#187164) 2026-05-28 katelovett@google.com Revert "[pubspec] Bump Dart SDK constraint to ^3.13.0 (#186957)" (flutter/flutter#187209) 2026-05-28 engine-flutter-autoroll@skia.org Roll Skia from f1b8ba877c07 to 32acea791248 (3 revisions) (flutter/flutter#187220) 2026-05-27 engine-flutter-autoroll@skia.org Roll Fuchsia Linux SDK from k9EizfEGJO4WwQN9-... to SBpmmPxqx3lAvGojE... (flutter/flutter#187211) 2026-05-27 bdero@google.com [Impeller] Add block-compressed texture format support (BC, ETC2, ASTC) (flutter/flutter#187077) 2026-05-27 katelovett@google.com Disable analyzer (flutter/flutter#187205) 2026-05-27 bdero@google.com [Flutter GPU] Add explicit draw counts (reland) (flutter/flutter#187192) 2026-05-27 bdero@google.com [Flutter GPU] Inject per-backend defines into shader bundle compilation (flutter/flutter#187081) 2026-05-27 engine-flutter-autoroll@skia.org Roll Skia from fa944af10f91 to f1b8ba877c07 (13 revisions) (flutter/flutter#187194) 2026-05-27 47866232+chunhtai@users.noreply.github.com Fixes bug when changing accessibilityFocusBlockType doesn't update ch… (flutter/flutter#186596) 2026-05-27 137456488+flutter-pub-roller-bot@users.noreply.github.com Roll pub packages (flutter/flutter#187191) 2026-05-27 kevmoo@users.noreply.github.com [web, tool] Support recompiling shaders and unify asset processing (2nd try) (flutter/flutter#186902) 2026-05-27 robert.ancell@canonical.com Fix crash if FlView is destroyed during a draw. (flutter/flutter#186848) 2026-05-27 engine-flutter-autoroll@skia.org Roll Packages from fc795e5 to 4b424d7 (4 revisions) (flutter/flutter#187174) 2026-05-27 15619084+vashworth@users.noreply.github.com Stop prefetching Swift packages in pub get (flutter/flutter#187113) 2026-05-27 jesswon@google.com Update CI with newer android sdk package (flutter/flutter#187143) 2026-05-27 jason-simmons@users.noreply.github.com Add a tag to the Linux platform properties in .ci.yaml that specifies x64 CPUs (flutter/flutter#187124) 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 boetger@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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…r#11799) flutter/flutter@c8f2f16...e70534d 2026-05-28 30870216+gaaclarke@users.noreply.github.com Linux glyph gamma correction (flutter/flutter#187122) 2026-05-28 chris@bracken.jp [iOS] Eliminate strong retain cycle from VSyncClient (flutter/flutter#187164) 2026-05-28 katelovett@google.com Revert "[pubspec] Bump Dart SDK constraint to ^3.13.0 (#186957)" (flutter/flutter#187209) 2026-05-28 engine-flutter-autoroll@skia.org Roll Skia from f1b8ba877c07 to 32acea791248 (3 revisions) (flutter/flutter#187220) 2026-05-27 engine-flutter-autoroll@skia.org Roll Fuchsia Linux SDK from k9EizfEGJO4WwQN9-... to SBpmmPxqx3lAvGojE... (flutter/flutter#187211) 2026-05-27 bdero@google.com [Impeller] Add block-compressed texture format support (BC, ETC2, ASTC) (flutter/flutter#187077) 2026-05-27 katelovett@google.com Disable analyzer (flutter/flutter#187205) 2026-05-27 bdero@google.com [Flutter GPU] Add explicit draw counts (reland) (flutter/flutter#187192) 2026-05-27 bdero@google.com [Flutter GPU] Inject per-backend defines into shader bundle compilation (flutter/flutter#187081) 2026-05-27 engine-flutter-autoroll@skia.org Roll Skia from fa944af10f91 to f1b8ba877c07 (13 revisions) (flutter/flutter#187194) 2026-05-27 47866232+chunhtai@users.noreply.github.com Fixes bug when changing accessibilityFocusBlockType doesn't update ch… (flutter/flutter#186596) 2026-05-27 137456488+flutter-pub-roller-bot@users.noreply.github.com Roll pub packages (flutter/flutter#187191) 2026-05-27 kevmoo@users.noreply.github.com [web, tool] Support recompiling shaders and unify asset processing (2nd try) (flutter/flutter#186902) 2026-05-27 robert.ancell@canonical.com Fix crash if FlView is destroyed during a draw. (flutter/flutter#186848) 2026-05-27 engine-flutter-autoroll@skia.org Roll Packages from fc795e5 to 4b424d7 (4 revisions) (flutter/flutter#187174) 2026-05-27 15619084+vashworth@users.noreply.github.com Stop prefetching Swift packages in pub get (flutter/flutter#187113) 2026-05-27 jesswon@google.com Update CI with newer android sdk package (flutter/flutter#187143) 2026-05-27 jason-simmons@users.noreply.github.com Add a tag to the Linux platform properties in .ci.yaml that specifies x64 CPUs (flutter/flutter#187124) 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 boetger@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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…on (flutter#187081) Adds the `IMPELLER_TARGET_*` define per backend when compiling a shader bundle, just like the rest of ImpellerC's shader compilation modes. Tests cover the per-backend define mapping, and verify end to end that a shader guarded by `#ifdef IMPELLER_TARGET_OPENGLES` is now compiled with that branch active for the OpenGLES backend. ## 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]. - [ ] 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. <!-- 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/ [breaking change policy]: https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md#handling-breaking-changes [Data Driven Fixes]: https://github.com/flutter/flutter/blob/main/docs/contributing/Data-driven-Fixes.md
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Adds the
IMPELLER_TARGET_*define per backend when compiling a shader bundle, just like the rest of ImpellerC's shader compilation modes.Tests cover the per-backend define mapping, and verify end to end that a shader guarded by
#ifdef IMPELLER_TARGET_OPENGLESis now compiled with that branch active for the OpenGLES backend.Pre-launch Checklist
///).