The expected color values appear to match the output of Skia's raster
backend's blur. Historically, that doesn't support any tile mode other
than decal, so while the `makeBlur()` function defaulted to clamp
tiling, the output was decal and thus showed the blur fading to
transparent.
The test draws a 1x1 green rectangle in the center of a 3x3 image. Clamp
tiling would actually cause the output of the blur to just copy the
central green color to the remaining 8 pixels. This is the output of
Skia's GPU blur. I am working to land changes in Skia that make the
raster backend handle all tile modes, which then has it match the
existing GPU blur's behavior of a constant output for clamp tiling in
this test (so it then fails).
Decal tiling appears to be more useful for this test case anyways
because it creates per-pixel variations that can be validated against.
This is needed to land Skia-side fixes for skbug.com/40039877 and
skbug.com/40039025
## 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] and the [C++,
Objective-C, Java style guides].
- [x] I listed at least one issue that this PR fixes in the description
above.
- [x] I added new tests to check the change I am making or feature I am
adding, or Hixie said the PR is test-exempt. See [testing the engine]
for instructions on writing and running engine tests.
- [x] I updated/added relevant documentation (doc comments with `///`).
- [x] I signed the [CLA].
- [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/wiki/Tree-hygiene#overview
[Tree Hygiene]: https://github.com/flutter/flutter/wiki/Tree-hygiene
[Flutter Style Guide]:
https://github.com/flutter/flutter/wiki/Style-guide-for-Flutter-repo
[C++, Objective-C, Java style guides]:
https://github.com/flutter/engine/blob/main/CONTRIBUTING.md#style
[testing the engine]:
https://github.com/flutter/flutter/wiki/Testing-the-engine
[CLA]: https://cla.developers.google.com/
[flutter/tests]: https://github.com/flutter/tests
[breaking change policy]:
https://github.com/flutter/flutter/wiki/Tree-hygiene#handling-breaking-changes
[Discord]: https://github.com/flutter/flutter/wiki/Chat
9cec508891