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Fix card focus transitions and scroll offset synchronization on iOS. #1970

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Merged
davidz25 merged 1 commit into from
Aug 29, 2026
Merged

Fix card focus transitions and scroll offset synchronization on iOS. #1970

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26 changes: 6 additions & 20 deletions multipaz-swiftui/src/iosMain/swift/VerticalCardList.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -211,23 +211,9 @@ private struct ScrollViewObserver: UIViewRepresentable {
guard !isUpdatingOffset else { return }
guard !scrollView.isDragging && !scrollView.isDecelerating && !scrollView.isTracking else { return }
let topInset = scrollView.adjustedContentInset.top
guard topInset > 0 || scrollView.window == nil else { return }

let visibleHeight = scrollView.bounds.height - topInset - scrollView.adjustedContentInset.bottom
let totalHeight = parent.state.totalHeight
let maxRelativeOffset = (visibleHeight > 0 && totalHeight > 0)
? max(0, totalHeight - visibleHeight)
: CGFloat.greatestFiniteMagnitude

var clampedScrollOffset = parent.state.scrollOffset
if parent.state.internalFocusedCardIdentifier == nil && clampedScrollOffset > maxRelativeOffset {
clampedScrollOffset = maxRelativeOffset
parent.state.scrollOffset = clampedScrollOffset
parent.state.model.scrollOffset = Double(clampedScrollOffset)
}

let baseOffset = -topInset
let targetOffset = baseOffset + clampedScrollOffset
let targetOffset = baseOffset + parent.state.scrollOffset
if abs(scrollView.contentOffset.y - targetOffset) > 0.5 {
isUpdatingOffset = true
scrollView.contentOffset.y = targetOffset
Expand All @@ -245,7 +231,6 @@ private struct ScrollViewObserver: UIViewRepresentable {
guard !self.isUpdatingOffset else { return }
guard scrollView.isDragging || scrollView.isDecelerating || scrollView.isTracking else { return }
let topInset = scrollView.adjustedContentInset.top
guard topInset > 0 else { return }
let newRelativeOffset = max(0, scrollView.contentOffset.y + topInset)
if abs(self.parent.state.scrollOffset - newRelativeOffset) > 0.5 {
self.parent.state.scrollOffset = newRelativeOffset
Expand Down Expand Up @@ -488,7 +473,7 @@ public struct VerticalCardList<TopContent: View, EmptyContent: View, SelectedCon
canAnimate: Bool
) -> some View {
let cardDim = layout.getDimensions(cardIdentifier: cardInfo.identifier)
let effectiveFocusedId = isAnyFocused ? (internalFocusedCard?.identifier ?? (animateListTransitions ? state.internalFocusedCardIdentifier : focusedCard?.identifier)) : nil
let effectiveFocusedId = isAnyFocused ? (internalFocusedCard?.identifier ?? state.internalFocusedCardIdentifier) : nil
let visualState = CardListLayoutCalculator.shared.computeCardVisualState(
cardIdentifier: cardInfo.identifier,
index: Int32(index),
Expand All @@ -499,7 +484,6 @@ public struct VerticalCardList<TopContent: View, EmptyContent: View, SelectedCon
draggedCardIdentifier: state.draggedCardIdentifier,
dragCurrentY: Double(state.dragCurrentY)
)
let isDragged = cardInfo.identifier == state.draggedCardIdentifier

ZStack(alignment: .topTrailing) {
Image(uiImage: cardInfo.cardArt)
Expand Down Expand Up @@ -679,8 +663,8 @@ public struct VerticalCardList<TopContent: View, EmptyContent: View, SelectedCon
} else {
focusedCard?.identifier
}
let isAnyFocused = focusedCard != nil && effectiveFocusedCardIdentifier != nil
let internalFocusedCard: CardInfo? = (focusedCard == nil) ? nil : cardInfos.first {
let isAnyFocused = effectiveFocusedCardIdentifier != nil
let internalFocusedCard: CardInfo? = cardInfos.first {
$0.identifier == effectiveFocusedCardIdentifier
}
let effectiveShowTopContent = if TopContent.self == EmptyView.self {
Expand Down Expand Up @@ -773,6 +757,8 @@ public struct VerticalCardList<TopContent: View, EmptyContent: View, SelectedCon
state.model.lastFocusedCardIdentifier = focusedCard?.identifier
}
}
} else {
state.internalFocusedCardIdentifier = focusedCard?.identifier
}
} else {
state.internalFocusedCardIdentifier = focusedCard?.identifier
Expand Down
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