8bd06c09be
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Reverts: flutter/flutter#169293
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Initiated by: matanlurey
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Reason for reverting: Does not work on Metal (iOS/macOS):
```
The following _Exception was thrown running a test:
Exception: Asset 'shaders/stretch_effect.frag' does not contain appropriate runtime stage data for current backend (Metal).
```
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Original PR Author: MTtankkeo
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Reviewed By: {dkwingsmt, justinmc, chunhtai}
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This change reverts the following previous change:
> 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].
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[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
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Co-authored-by: auto-submit[bot] <flutter-engprod-team@google.com>
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