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fix(ios): hit-test nested scrollables from the touch-down point instead of the post-threshold pan location #71

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Merged
patrickmichalik merged 1 commit into from
Aug 15, 2026
Merged

fix(ios): hit-test nested scrollables from the touch-down point instead of the post-threshold pan location #71

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19 changes: 17 additions & 2 deletions ios/BottomSheetHostingView.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -177,6 +177,7 @@ public final class BottomSheetHostingView: UIView {
private var isPanning = false
private var lastReportedInvalidDetentMessage: String?
private var panStartingIndex: Int?
private var initialTouchLocation: CGPoint?
private var activeDragRange: (minTy: CGFloat, maxTy: CGFloat)?
private var activeDragDetentSpecs: [DetentSpec]?
private var activeScrollViewStates: [ActiveScrollViewState] = []
Expand Down Expand Up @@ -881,7 +882,7 @@ public final class BottomSheetHostingView: UIView {
scrollViewOwnsLowerBoundary = false
activeScrollableNegotiationLevel = negotiationLevel(forVerticalVelocity: gesture.velocity(in: self).y)

let locationInContainer = gesture.location(in: sheetContainer)
let locationInContainer = initialTouchLocation ?? gesture.location(in: sheetContainer)
activeScrollViewStates = scrollableAncestorChain(containing: locationInContainer).map {
ActiveScrollViewState(scrollView: $0.scrollView, inverted: $0.inverted)
}
Expand Down Expand Up @@ -1227,7 +1228,7 @@ public final class BottomSheetHostingView: UIView {
let candidates = snapCandidateIndices(including: targetIndex)
guard candidates.count > 1 else { return false }

let locationInContainer = panGesture.location(in: sheetContainer)
let locationInContainer = initialTouchLocation ?? panGesture.location(in: sheetContainer)
let scrollableChain = scrollableAncestorChain(containing: locationInContainer)
guard !scrollableChain.isEmpty else {
// Outside a scrollable, the sheet owns any direction in which it has a
Expand Down Expand Up @@ -1561,6 +1562,20 @@ extension BottomSheetHostingView: UIGestureRecognizerDelegate {
return true
}

public func gestureRecognizer(
_ gestureRecognizer: UIGestureRecognizer,
shouldReceive touch: UITouch
) -> Bool {
// Record the touch-down point before the pan's translation threshold is
// exceeded. gestureRecognizerShouldBegin and handlePan(.began) hit-test
// scrollables from this point instead of the post-threshold pan location,
// matching Android's ACTION_DOWN semantics.
if gestureRecognizer === panGesture, panGesture.numberOfTouches == 0 {
initialTouchLocation = touch.location(in: sheetContainer)
}
return true
}

public func gestureRecognizer(
_ gestureRecognizer: UIGestureRecognizer,
shouldBeRequiredToFailBy other: UIGestureRecognizer
Expand Down