fix(ios): learn detent offset before present transition emits positions

[lodev09]

Summary

onPositionChange emitted a slightly fractional index (e.g. ~0.07 instead of 0) during the present transition, then snapped to the exact detent index right after didPresent — visible as a small jump on anything animated with index (e.g. a footer translated via reanimated).

Cause: the resolver-vs-actual detent offset (bottom safe area etc.) is only learned in viewDidAppear, drag end, and detent change — so the interpolation during the present animation ran against uncorrected detent heights, and the first correct emit happened after present.

Fix: learn the offset at the start of the present transition in setupTransitionTracker, before the display link emits positions. The presented frame is already final there (the same assumption presentedFrame capture relies on), and the resolverHeight > 0 guard keeps it a no-op if the detent resolver hasn't run (including iOS < 16).

Type of Change

• Bug fix
• New feature
• Breaking change
• Documentation update

Test Plan

Reproduced in a consumer app with ['peek', <fraction>] detents and a footer animated off onPositionChange index: footer nudged right after present. With this change the index lands exactly at the target detent and the footer stays put. Regression-checked present → drag between detents → dismiss.

Checklist

• I tested on iOS
• I tested on Android
• I tested on Web
• I updated the documentation (if needed)
• I added a changelog entry (if needed)

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Project	Deployment	Actions	Updated (UTC)
react-native-true-sheet	Ready	Preview, Comment	Jul 12, 2026 3:32pm

[lodev09]

🚀 This pull request is included in v3.11.6. See Release 3.11.6 for release notes.