Fix Hit Tests in RenderEditable when Scrolled

[creativecreatorormaybenot]

This fixes hitTestChildren in RenderEditable by respecting the scroll offset (_paintOffset for applying the scroll axis).

Before, hit tests were broken when the EditableText/TextField was scrolled.

Issues

Fixes #81038.

Tests

The first test case I added was passing before (making sure that my change does not make that fail) and the latter two test cases were failing before.

Pre-launch Checklist

• I read the Contributor Guide and followed the process outlined there for submitting PRs.
• I read the Tree Hygiene wiki page, which explains my responsibilities.
• I read and followed the Flutter Style Guide, including Features we expect every widget to implement.
• I signed the CLA.
• I listed at least one issue that this PR fixes in the description above.
• I updated/added relevant documentation (doc comments with ///).
• I added new tests to check the change I am making or feature I am adding, or Hixie said the PR is test-exempt.
• All existing and new tests are passing.

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[flutter-dashboard]

It looks like this pull request may not have tests. Please make sure to add tests before merging. If you need an exemption to this rule, contact Hixie on the #hackers channel in Chat.

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[LongCatIsLooong]

The change looks good to me. Could you create a RenderEditable with a non-zero offset, and call hitTest on it to see if the method is doing the right thing? It's probably the easiest to follow the example of tests in "test/rendering/editable_test.dart"

[creativecreatorormaybenot]

@LongCatIsLooong Thanks for the hint. I am working on the tests and will probably have them ready in a few 👍

[creativecreatorormaybenot]

I added the test cases 👍 Note that the first test case I added was passing before (making sure that my change does not make that fail) and the latter two test cases were failing before.