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Display/ListView: pin first pinToEdgeWithInset item to bottom edge

Browse source 
Introduces a pin-to-edge mode for list items: items whose
pinToEdgeWithInset flag is true are pinned to the bottom edge of the
visible area, with the list geometry (pin inset, scrollToItem,
inset-transition offsetFix, visible-size updates) adjusted to handle
this new mode consistently.

Collected from spec, plan, and 12 iterative fixes during
implementation that refined pin-inset helpers, scroll landings, and
transition math. Pin-inset computation uses frame.size.height;
scrollToItem lands on the item's pinned position via apparentBounds.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
This commit is contained in:
Isaac 2026-04-19 23:45:13 +02:00
parent bedbc8de6d
commit 4bd54b9771
3 changed files with 544 additions and 14 deletions
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90
submodules/Display/Source/ListView.swift
View file

@ -1073,22 +1073,49 @@ open class ListViewImpl: ASDisplayNode, ListView, ASScrollViewDelegate, ASGestur
if remainingFactor.isLessThanOrEqualTo(0.0) {
break
}
let itemFactor: CGFloat
if CGFloat(1.0).isLessThanOrEqualTo(remainingFactor) {
itemFactor = 1.0
} else {
itemFactor = remainingFactor
}
additionalInverseTopInset += floor(itemNode.apparentBounds.height * itemFactor)
remainingFactor -= 1.0
}
}
return additionalInverseTopInset
}
private func calculatePinToEdgeTopInset() -> CGFloat {
var lowestPinnedIndex: Int = Int.max
for itemNode in self.itemNodes {
guard let index = itemNode.index, index >= 0, index < self.items.count else { continue }
if index < lowestPinnedIndex && self.items[index].pinToEdgeWithInset {
lowestPinnedIndex = index
}
}
guard lowestPinnedIndex != Int.max else { return 0.0 }
var totalAboveAndPinned: CGFloat = 0.0
var sawIndexZero = false
for itemNode in self.itemNodes {
guard let index = itemNode.index else { continue }
if index == 0 {
sawIndexZero = true
}
if index <= lowestPinnedIndex {
totalAboveAndPinned += itemNode.apparentBounds.height
}
}
guard sawIndexZero else { return 0.0 }
let visibleArea = self.visibleSize.height - self.insets.top - self.insets.bottom
return max(0.0, visibleArea - totalAboveAndPinned)
}
private func areAllItemsOnScreen() -> Bool {
if self.itemNodes.count == 0 {
return true
@ -1183,7 +1210,11 @@ open class ListViewImpl: ASDisplayNode, ListView, ASScrollViewDelegate, ASGestur
let additionalInverseTopInset = self.calculateAdditionalTopInverseInset()
effectiveInsets.top = max(effectiveInsets.top, self.visibleSize.height - additionalInverseTopInset)
}
let pinToEdgeTopInset = self.calculatePinToEdgeTopInset()
if pinToEdgeTopInset > 0.0 {
effectiveInsets.top = max(effectiveInsets.top, self.insets.top + pinToEdgeTopInset)
}
if topItemFound {
topItemEdge = self.itemNodes[0].apparentFrame.origin.y - self.tempTopInset
}
@ -1614,7 +1645,11 @@ open class ListViewImpl: ASDisplayNode, ListView, ASScrollViewDelegate, ASGestur
let additionalInverseTopInset = self.calculateAdditionalTopInverseInset()
effectiveInsets.top = max(effectiveInsets.top, self.visibleSize.height - additionalInverseTopInset)
}
let pinToEdgeTopInset = self.calculatePinToEdgeTopInset()
if pinToEdgeTopInset > 0.0 {
effectiveInsets.top = max(effectiveInsets.top, self.insets.top + pinToEdgeTopInset)
}
completeHeight = effectiveInsets.top + effectiveInsets.bottom
if let index = self.itemNodes[self.itemNodes.count - 1].index, index == self.items.count - 1 {
@ -3022,13 +3057,31 @@ open class ListViewImpl: ASDisplayNode, ListView, ASScrollViewDelegate, ASGestur
if let scrollToItem = scrollToItem, !self.areAllItemsOnScreen() || !sizeOrInsetsUpdated {
self.stopScrolling()
for itemNode in self.itemNodes {
if let index = itemNode.index, index == scrollToItem.index {
let insets = self.insets// updateSizeAndInsets?.insets ?? self.insets
var isPinToEdgeTarget = false
if self.calculatePinToEdgeTopInset() > 0.0,
index >= 0, index < self.items.count,
self.items[index].pinToEdgeWithInset {
isPinToEdgeTarget = true
for otherNode in self.itemNodes {
guard let otherIndex = otherNode.index else { continue }
guard otherIndex >= 0, otherIndex < self.items.count else { continue }
if otherIndex < index, self.items[otherIndex].pinToEdgeWithInset {
isPinToEdgeTarget = false
break
}
}
}
var offset: CGFloat
switch scrollToItem.position {
if isPinToEdgeTarget {
offset = (self.visibleSize.height - insets.bottom) - itemNode.apparentFrame.maxY + itemNode.scrollPositioningInsets.bottom
} else {
switch scrollToItem.position {
case let .bottom(additionalOffset):
offset = (self.visibleSize.height - insets.bottom) - itemNode.apparentFrame.maxY + itemNode.scrollPositioningInsets.bottom + additionalOffset
case let .top(additionalOffset):
@ -3066,8 +3119,9 @@ open class ListViewImpl: ASDisplayNode, ListView, ASScrollViewDelegate, ASGestur
offset = 0.0
}
}
}
}
for itemNode in self.itemNodes {
var frame = itemNode.frame
frame.origin.y += offset
@ -3126,10 +3180,12 @@ open class ListViewImpl: ASDisplayNode, ListView, ASScrollViewDelegate, ASGestur
if let updateSizeAndInsets = updateSizeAndInsets {
if self.insets != updateSizeAndInsets.insets || self.headerInsets != updateSizeAndInsets.headerInsets || !self.visibleSize.height.isEqual(to: updateSizeAndInsets.size.height) {
let previousPinToEdgeTopInset = self.calculatePinToEdgeTopInset()
let previousVisibleSize = self.visibleSize
self.visibleSize = updateSizeAndInsets.size
var offsetFix: CGFloat
var offsetFixUsesEffectiveTopInset = false
let insetDeltaOffsetFix: CGFloat = 0.0
if (self.isTracking && !self.allowInsetFixWhileTracking) || isExperimentalSnapToScrollToItem {
offsetFix = 0.0
@ -3137,17 +3193,23 @@ open class ListViewImpl: ASDisplayNode, ListView, ASScrollViewDelegate, ASGestur
offsetFix = -updateSizeAndInsets.insets.bottom + self.insets.bottom
} else {
offsetFix = updateSizeAndInsets.insets.top - self.insets.top
offsetFixUsesEffectiveTopInset = true
}
offsetFix += additionalScrollDistance
self.insets = updateSizeAndInsets.insets
self.headerInsets = updateSizeAndInsets.headerInsets ?? self.insets
self.scrollIndicatorInsets = updateSizeAndInsets.scrollIndicatorInsets ?? self.insets
self.itemOffsetInsets = updateSizeAndInsets.itemOffsetInsets
self.ensureTopInsetForOverlayHighlightedItems = updateSizeAndInsets.ensureTopInsetForOverlayHighlightedItems
self.visibleSize = updateSizeAndInsets.size
if offsetFixUsesEffectiveTopInset {
let updatedPinToEdgeTopInset = self.calculatePinToEdgeTopInset()
offsetFix += updatedPinToEdgeTopInset - previousPinToEdgeTopInset
}
for itemNode in self.itemNodes {
itemNode.updateFrame(itemNode.frame.offsetBy(dx: 0.0, dy: offsetFix), within: self.visibleSize, transition: customAnimationTransition)
}