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fix: make sure initialScrollIndex is bigger than 0 #36844

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fix: make sure initialScrollIndex is bigger than 0 #36844

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5 changes: 3 additions & 2 deletions packages/virtualized-lists/Lists/VirtualizedList.js
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Original file line number Diff line number Diff line change
Expand Up @@ -616,7 +616,7 @@ class VirtualizedList extends StateSafePureComponent<Props, State> {
),
};
} else {
// If we have a non-zero initialScrollIndex and run this before we've scrolled,
// If we have a positive non-zero initialScrollIndex and run this before we've scrolled,
// we'll wipe out the initialNumToRender rendered elements starting at initialScrollIndex.
// So let's wait until we've scrolled the view to the right place. And until then,
// we will trust the initialScrollIndex suggestion.
Expand All @@ -627,7 +627,8 @@ class VirtualizedList extends StateSafePureComponent<Props, State> {
// - initialScrollIndex > 0 AND the end of the list is visible (this handles the case
// where the list is shorter than the visible area)
if (
props.initialScrollIndex &&
props.initialScrollIndex != null &&
props.initialScrollIndex > 0 &&
!this._scrollMetrics.offset &&
Math.abs(distanceFromEnd) >= Number.EPSILON
) {
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53 changes: 47 additions & 6 deletions packages/virtualized-lists/Lists/__tests__/__snapshots__/VirtualizedList-test.js.snap
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Expand Up @@ -3122,12 +3122,53 @@ exports[`gracefully handles negative initialScrollIndex 1`] = `
/>
</View>
<View
style={
Object {
"height": 60,
}
}
/>
onFocusCapture={[Function]}
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@lunaleaps lunaleaps Apr 6, 2023

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Is this change expected? It looks this is the snapshot from

react-native/packages/virtualized-lists/Lists/__tests__/VirtualizedList-test.js

Line 828 in a27270f

it('gracefully handles negative initialScrollIndex', () => {

which lists initialNumToRender as 4

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@NickGerleman NickGerleman Apr 7, 2023

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It looks like the snapshot is taken after we run fake layout and timers (after initial render), so I think this is showing that we are now rendering cells we previously failed to.

style={null}
>
<MockCellItem
value={4}
/>
</View>
<View
onFocusCapture={[Function]}
style={null}
>
<MockCellItem
value={5}
/>
</View>
<View
onFocusCapture={[Function]}
style={null}
>
<MockCellItem
value={6}
/>
</View>
<View
onFocusCapture={[Function]}
style={null}
>
<MockCellItem
value={7}
/>
</View>
<View
onFocusCapture={[Function]}
style={null}
>
<MockCellItem
value={8}
/>
</View>
<View
onFocusCapture={[Function]}
style={null}
>
<MockCellItem
value={9}
/>
</View>
</View>
</RCTScrollView>
`;
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