callstack / callstack/react-native-pager-view

[iOS] pager content getting cropped on version 8.0.4

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Descrizione

## Environment

react-native-pager-view: 8.0.4 (regression from 8.0.2)
react-native: 0.81.1
Architecture: Fabric (New Architecture)
Platform: iOS
Device: iPhone 16 Pro, portrait (reproduces on any device with a home-indicator safe area)
Tab bar: custom React Native bottom tab (not the system UITabBar)

## Description

Regression in 8.0.4, introduced by [#1085](https://github.com/Groww/lucifer/issues/1085).

After upgrading 8.0.2 → 8.0.4, page content is cropped at the bottom on first render and only corrects after the first scroll.

Root cause (confirmed with native logging inside PageChildViewController):

propagateSafeArea() walks up to the nearest ancestor with a non-zero safe area and copies its safeAreaInsets into additionalSafeAreaInsets. The picked source is consistently the same view (_UIHostingView<_ViewList_View>), but its safeAreaInsets.bottom is not stable during layout — it flickers 49 → 24.33 while the hosting view's height settles through intermediate passes (730 → 681 → 656.66).

propagateSafeArea() samples this value mid-relayout and pins the transient 24.33, cropping the content. The 0.5pt guard doesn't help, since 49 → 24.33 is a large delta (the guard only prevents infinite layout loops, not incorrect values). A manual scroll forces a clean relayout back to 49, which is why the crop disappears after scrolling.

Trigger: the initial layout pass on first mount, and again whenever the page is relaid out. The inset is read while the hosting view's layout is still settling, so an intermediate value gets applied.

Expected: content uses the correct, stable bottom inset (49) on first render.
Actual: content is cropped using a transient inset (24.33) until the first scroll.

## Reproducible Demo

Fabric app with a PagerView whose page contains a scrollable list.
The page is rendered inside a view whose height changes during initial layout (below a collapsing header or header height changes during layout).
On first load, the bottom of the content is cut off. Scroll once and it corrects.

Image

Guida per i contributori

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Direzione di ricerca

Inizia tracciando propagateSafeArea() da PageChildViewController e confronta la regressione introdotta da issue #1085. Riproduci il layout di Fabric iOS con una pagina di altezza variabile, quindi verifica che l'inset inferiore rimanga stabile e che il contenuto non venga ritagliato né al primo rendering né dopo il relayout.

Scritto dal modello di indicizzazione a partire dal testo della issue.

Valutazione

Stack tecnologico
ios, react-native, typescript
Ambito
mobile
Tipo di issue
Bug
Difficoltà
4/5
Tempo stimato
3-5 giorni
Stato di attività
Attiva
Chiarezza
Abbastanza chiara
Idoneità per principianti
55/100

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