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> Sorry, Closing PR #169196 and reopening this in a new PR for clarity and a cleaner commit history. Fixes #82906 In the existing Flutter implementation, the Android stretch overscroll effect is achieved using Transform. However, this approach does not evenly stretch the screen as it does in the native Android environment. Therefore, in the Impeller environment, add or modify files to implement the effect using a fragment shader identical to the one used in native Android. > [!NOTE] > - The addition of a separate test file for StretchOverscrollEffect was not included because it would likely duplicate coverage already provided by the changes made in overscroll_stretch_indicator_test.dart within this PR. >> However, since determining whether stretching occurred by referencing global coordinates is currently considered impossible with the new Fragment Shader approach, the code was modified to partially exclude the relevant test logic in the Impeller. >> >> For reference, in the page_view_test.dart test, there was an issue with referencing the child Transform widget, but because the StretchOverscrollEffect widget is defined instead of the Transform widget in the Impeller environment, the code logic was adjusted accordingly. > > - Golden image tests were updated as the visual effect changes. ## Reference Source - https://cs.android.com/android/platform/superproject/main/+/main:frameworks/base/libs/hwui/effects/StretchEffect.cpp ## `Old` Skia (Using Transform) https://github.com/user-attachments/assets/22d8ff96-d875-4722-bf6f-f0ad15b9077d ## `New` Impeller (Using fragment shader) https://github.com/user-attachments/assets/73b6ef18-06b2-42ea-9793-c391ec2ce282 ## 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. - [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]. <!-- 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 --------- Co-authored-by: Tong Mu <dkwingsmt@users.noreply.github.com> Co-authored-by: Kate Lovett <katelovett@google.com>