Add the focus state related methods to the platform dispatcher

[tugorez]

This change augments the platform dispatcher to allow the engine <===> framework to communicate flutter and platform focus changes.

Relevant Issues are:

• Design doc link: https://github.com/flutter/website/actions/runs/7560898849/job/20588395967
• Design doc: Focus management flutter#141711
• Focus in web multiview: [web:multi-view] Make keyboard and focus multi-view aware flutter#137443

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 and the C++, Objective-C, Java style guides.
• I listed at least one issue that this PR fixes in the description above.
• I added new tests to check the change I am making or feature I am adding, or the PR is test-exempt. See testing the engine for instructions on writing and running engine tests.
• I updated/added relevant documentation (doc comments with ///).
• I signed the CLA.
• All existing and new tests are passing.

If you need help, consider asking for advice on the #hackers-new channel on Discord.

[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 "@test-exemption-reviewer" in the #hackers channel in Chat (don't just cc them here, they won't see it! Use Discord!).

If you are not sure if you need tests, consider this rule of thumb: the purpose of a test is to make sure someone doesn't accidentally revert the fix. Ask yourself, is there anything in your PR that you feel it is important we not accidentally revert back to how it was before your fix?

Reviewers: Read the Tree Hygiene page and make sure this patch meets those guidelines before LGTMing.

[goderbauer]

I like the structure of this API now. I mostly have suggestions for improving the docs.

@gspencergoog Should also take a look at this in case he ends up implementing the framework side that will consume this API.

[goderbauer]

API LGTM

[zanderso]

This PR is causing analysis to fail in snippet code on rolling to the framework: https://ci.chromium.org/ui/p/flutter/builders/try/Linux%20analyze/73029/overview. I added the revert tag.

[zanderso]

RUNNING: cd .; bin/cache/dart-sdk/bin/dart --enable-asserts /b/s/w/ir/x/w/flutter/dev/bots/analyze_snippet_code.dart --verbose
workingDirectory: /b/s/w/ir/x/w/flutter, executable: /b/s/w/ir/x/w/flutter/bin/cache/dart-sdk/bin/dart, arguments: [--enable-asserts, /b/s/w/ir/x/w/flutter/dev/bots/analyze_snippet_code.dart, --verbose]
bin/cache/pkg/sky_engine/lib/ui/platform_dispatcher.dart:320:7: The function 'ViewFocusEvent' isn't defined (expression) (undefined_function)
bin/cache/pkg/sky_engine/lib/ui/platform_dispatcher.dart:322:16: Undefined name 'ViewFocusState' (expression) (undefined_identifier)
bin/cache/pkg/sky_engine/lib/ui/platform_dispatcher.dart:323:20: Undefined name 'ViewFocusDirection' (expression) (undefined_identifier)
bin/cache/pkg/sky_engine/lib/ui/platform_dispatcher.dart:338:7: The function 'ViewFocusEvent' isn't defined (expression) (undefined_function)
bin/cache/pkg/sky_engine/lib/ui/platform_dispatcher.dart:340:16: Undefined name 'ViewFocusState' (expression) (undefined_identifier)
bin/cache/pkg/sky_engine/lib/ui/platform_dispatcher.dart:341:20: Undefined name 'ViewFocusDirection' (expression) (undefined_identifier)
bin/cache/pkg/sky_engine/lib/ui/platform_dispatcher.dart:376:16: Undefined name 'ViewFocusSate' (statement) (undefined_identifier)
bin/cache/pkg/sky_engine/lib/ui/platform_dispatcher.dart:377:20: Undefined name 'ViewFocusDirection' (statement) (undefined_identifier)
Found 8 snippet code errors.
See the documentation at the top of dev/bots/analyze_snippet_code.dart for details.

[tugorez]

This PR is causing analysis to fail in snippet code on rolling to the framework: https://ci.chromium.org/ui/p/flutter/builders/try/Linux%20analyze/73029/overview. I added the revert tag.

Oops, thanks for catching this. @zanderso is there any reason we don't have those linter checks enabled as part of the engine commit process?

[tugorez]

This PR is causing analysis to fail in snippet code on rolling to the framework: https://ci.chromium.org/ui/p/flutter/builders/try/Linux%20analyze/73029/overview. I added the revert tag.

Oops, thanks for catching this. @zanderso is there any reason we don't have those linter checks enabled as part of the engine commit process?

Also is there an easy way to verify these things locally?

[zanderso]

I'm not familiar with how the snippet analysis is implemented. I vaguely recall that @gspencergoog might know more about this.

[gspencergoog]

Snippet analysis happens in dev/bots/analyze_snippet_code.dart in the flutter repo. You can run it locally, but you'd have to (manually?) put the engine artifacts into the cache directory of your local flutter repo for it to catch these.

Perhaps that script should be added as part of the presumbits that the engine runs on the Flutter repo?