Fix iOS text field focus transfer across scenes

[Kyle (Kyle-Ye)]

This fixes iOS BasicTextField focus handoff when moving focus between separate Compose scenes, for example an outer ComposeUIViewController and a nested ComposeUIView.

The fix adds a shared UIKit text input focus coordinator that releases the previously focused Compose scene before a different scene starts text input.

Fixes https://youtrack.jetbrains.com/issue/CMP-10454/iOS-BasicTextField-focus-is-not-released-when-moving-between-nested-ComposeUIView-scenes

Testing

• Added NestedComposeTextFieldFocusTest.focusMovesToTextFieldInNestedComposeUIView
• Verified the regression test fails before the fix:
  Nested text field should take focus and release the outer text field
• Verified the same test passes after the fix:
  Executed 1 test, with 0 failures

Release Notes

Fixes - iOS

• Fix BasicTextField focus handoff between nested Compose iOS scenes.

Google CLA

Signed or will sign the Google Contributor License Agreement.

[Kyle (Kyle-Ye)]

Could you help review this PR? cc Vladimir Mazunin (@mazunin-v-jb)

[Andrei Salavei (ASalavei)]

Thank you for spotting the issue. Currently, we have onResignFocus handler that must prevent such cases. It seems like it does not handle all required cases, like youth. I would first try to reuse this approach instead of creating a new one to minimize duplicated logic. It would be great if you could modify the hasFocusedExternalInputViewInWindowHierarchy() to fix the problem.

[Kyle (Kyle-Ye)]

It would be great if you could modify the hasFocusedExternalInputViewInWindowHierarchy() to fix the problem.

Got it. And I have verified the previous dialog test case failure in the last CI pipeline is also fixed now.

Could you help review and approval the CI again for me? Andrei Salavei (@ASalavei)

[Vendula Švastalová (svastven)]

LGTM. Thanks for this PR 👍🏻

[Kyle (Kyle-Ye)]

Andrei Salavei (@ASalavei) Could you please approve and trigger the CI workflow again?

I fixed the iPad-only failure in NestedComposeTextFieldFocusTest in ec0d088. The tagged UIKitView was wider than its fixed-width nested ComposeUIView, so tapping the host center missed the nested field on iPad. The nested ComposeUIView now directly fills the tagged host bounds.

Local verification:

• iPhone 17 Pro / iOS 26.2: passed
• iPad Pro 11-inch (M5) / iOS 26.2: passed
• Temporarily reverting the production focus fix makes the regression test fail; restoring it makes the test pass.

The two Web failures in the previous run were unrelated kotlinNpmInstall 504 errors while fetching Kotlin/karma.

Thank you!

[Kyle (Kyle-Ye)]

The only remaining failure is Compose Desktop Tests, where two DialogWindowV2Test cases timed out after 30 seconds.

It looks unrelated to this PR, since the changes are limited to iosMain and uikitInstrumentedTest, and the same Desktop job passed in the previous run.

I think we should retry it. Thanks

[Kyle (Kyle-Ye)]

The retried Compose Desktop Tests job failed again, but this time in a different test: ComposeContainerLifecycleOwnerTest.allEvents
java.lang.AssertionError: expected:<ON_RESUME> but was:<null>

Let's rerun the job once more.