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fix: complete non-zero initialScrollIndex on iOS without waiting for native scroll events #500

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fix: complete non-zero initialScrollIndex on iOS without waiting for native scroll events #500

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08c84df
fix: complete non-zero initialScrollIndex on iOS without waiting for …
erank-pixel Jul 15, 2026
bfd2897
fix: only trust dispatched initial offsets on iOS for plain, in-range…
erank-pixel Jul 15, 2026
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34 changes: 29 additions & 5 deletions src/core/checkFinishedScroll.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -58,17 +58,41 @@ function isNativeInitialNonZeroTarget(state: StateContext["state"]) {
return !state.didFinishInitialScroll && initialScrollWatchdog.hasNonZeroTargetOffset(targetOffset);
}

function shouldFinishInitialScrollWithoutNativeProgress(state: StateContext["state"], scrollingTo: ActiveScrollTarget) {
function shouldFinishInitialScrollWithoutNativeProgress(ctx: StateContext, scrollingTo: ActiveScrollTarget) {
const { state } = ctx;
if (!scrollingTo.isInitialScroll || scrollingTo.animated || !state.didContainersLayout) {
return false;
}

if (state.initialScrollSession?.kind === "bootstrap") {
const targetOffset = scrollingTo.targetOffset ?? scrollingTo.offset;

// On iOS an unanimated initial scrollTo/contentOffset does NOT emit a
// scroll event, so gating completion on observing native scroll progress
// deadlocks plain initial targets: the fallback loop re-issues scrollTo to
// the same offset (which again emits nothing) until the watchdog gives up
// seconds later — all while the list is held at opacity 0.
//
// state.scroll is set optimistically at dispatch (doScrollTo.native.ts),
// so it is only trustworthy when the requested offset was actually
// applicable: a plain target (no viewOffset/viewPosition adjustment —
// those are recomputed on retries) that lies within the currently
// scrollable range (so native cannot have clamped it short). End-aligned /
// initialScrollAtEnd targets with footers can exceed the max scroll until
// late layout and must keep waiting for confirmed native progress, which
// their recomputed-offset retries do produce.
const maxScrollOffset = getContentSize(ctx) - state.scrollLength;
const canTrustDispatchedOffsetOnIOS =
Platform.OS === "ios" &&
!scrollingTo.viewOffset &&
!scrollingTo.viewPosition &&
targetOffset <= maxScrollOffset + 1;

if (!canTrustDispatchedOffsetOnIOS && state.initialScrollSession?.kind === "bootstrap") {
return false;
}

const targetOffset = scrollingTo.targetOffset ?? scrollingTo.offset;
if (
!canTrustDispatchedOffsetOnIOS &&
initialScrollWatchdog.hasNonZeroTargetOffset(targetOffset) &&
initialScrollCompletion.didDispatchNativeScroll(state) &&
!state.hasScrolled
Expand Down Expand Up @@ -166,7 +190,7 @@ export function checkFinishedScrollFallback(ctx: StateContext) {
const shouldFinishInitialZeroTarget = shouldFinishInitialZeroTargetScroll(ctx);
const silentInitialDispatch = isSilentInitialDispatch(state, scrollingTo);
const canFinishInitialWithoutNativeProgress =
scrollingTo !== undefined ? shouldFinishInitialScrollWithoutNativeProgress(state, scrollingTo) : false;
scrollingTo !== undefined ? shouldFinishInitialScrollWithoutNativeProgress(ctx, scrollingTo) : false;
const slowTimeout =
(scrollingTo?.isInitialScroll && !shouldFinishInitialZeroTarget && !canFinishInitialWithoutNativeProgress) ||
!state.didContainersLayout;
Expand Down Expand Up @@ -198,7 +222,7 @@ export function checkFinishedScrollFallback(ctx: StateContext) {
: 5;
const shouldFinishZeroTarget = shouldFinishInitialZeroTargetScroll(ctx);
const canFinishInitialScrollWithoutNativeProgress = shouldFinishInitialScrollWithoutNativeProgress(
state,
ctx,
isStillScrollingTo,
);
const completionState = getResolvedScrollCompletionState(ctx, isStillScrollingTo);
Expand Down