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Merged
bryankeller merged 3 commits into from
Nov 18, 2025
Merged

Bk/fix preferred attributes content offset adjustment #149

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d78aeb9
Fix target content offset anchor calculation
bryankeller Nov 17, 2025
6866839
Example project tweaks
bryankeller Nov 17, 2025
dcde318
Fix tests
bryankeller Nov 18, 2025
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18 changes: 1 addition & 17 deletions Example/MagazineLayoutExample/GridDemoViewController.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -291,23 +291,7 @@ extension GridDemoViewController: UICollectionViewDelegateMagazineLayout {

private struct GridItem: Hashable {

// MARK: Lifecycle

init(
id: UUID = UUID(),
text: String,
color: UIColor,
widthMode: MagazineLayoutItemWidthMode)
{
self.id = id
self.text = text
self.color = color
self.widthMode = widthMode
}

// MARK: Internal

let id: UUID
let id = UUID()
let text: String
let color: UIColor
let widthMode: MagazineLayoutItemWidthMode
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18 changes: 1 addition & 17 deletions Example/MagazineLayoutExample/ListDemoViewController.swift
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Expand Up @@ -383,23 +383,7 @@ private struct ListSection: Hashable {

private struct ListItem: Hashable {

// MARK: Lifecycle

init(
id: UUID = UUID(),
title: String,
subtitle: String,
color: UIColor)
{
self.id = id
self.title = title
self.subtitle = subtitle
self.color = color
}

// MARK: Internal

let id: UUID
let id = UUID()
let title: String
let subtitle: String
let color: UIColor
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4 changes: 1 addition & 3 deletions Example/MagazineLayoutExample/MessageThreadDemoViewController.swift
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Expand Up @@ -302,20 +302,18 @@ private struct Message: Hashable {
// MARK: Lifecycle

init(
id: UUID = UUID(),
text: String,
isSent: Bool,
timestamp: Date = Date())
{
self.id = id
self.text = text
self.isSent = isSent
self.timestamp = timestamp
}

// MARK: Internal

let id: UUID
let id = UUID()
let text: String
let isSent: Bool
let timestamp: Date
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4 changes: 3 additions & 1 deletion MagazineLayout/LayoutCore/LayoutState.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -64,6 +64,8 @@ struct LayoutState {
var targetContentOffsetAnchor: TargetContentOffsetAnchor {
var visibleItemLocationFramePairs = [ElementLocationFramePair]()
for itemLocationFramePair in modelState.itemLocationFramePairs(forItemsIn: bounds) {
// Only consider fully-visible items
guard bounds.contains(itemLocationFramePair.frame) else { continue }
visibleItemLocationFramePairs.append(itemLocationFramePair)
}
visibleItemLocationFramePairs.sort { $0.elementLocation < $1.elementLocation }
Expand All @@ -74,7 +76,7 @@ struct LayoutState {
modelState.isItemHeightSettled(indexPath: $0.elementLocation.indexPath)
} ?? visibleItemLocationFramePairs.first // fallback to the first item if we can't find one with a settled height

let lastVisibleItemLocationFramePair = visibleItemLocationFramePairs.reversed().first {
let lastVisibleItemLocationFramePair = visibleItemLocationFramePairs.last {
// When scrolling down, only calculate a target content offset based on visible, already-sized
// cells. Otherwise, scrolling will be jumpy.
modelState.isItemHeightSettled(indexPath: $0.elementLocation.indexPath)
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12 changes: 6 additions & 6 deletions Tests/LayoutStateTargetContentOffsetTests.swift
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Expand Up @@ -40,8 +40,8 @@ final class LayoutStateTargetContentOffsetTests: XCTestCase {
contentInset: UIEdgeInsets(top: 50, left: 0, bottom: 30, right: 0),
scale: 1,
verticalLayoutDirection: .topToBottom)
let id = layoutState.modelState.idForItemModel(at: IndexPath(item: 5, section: 0))!
XCTAssert(layoutState.targetContentOffsetAnchor == .topItem(id: id, distanceFromTop: -160))
let id = layoutState.modelState.idForItemModel(at: IndexPath(item: 6, section: 0))!
XCTAssert(layoutState.targetContentOffsetAnchor == .topItem(id: id, distanceFromTop: -25))
}

func testAnchor_TopToBottom_ScrolledToBottom() throws {
Expand All @@ -61,8 +61,8 @@ final class LayoutStateTargetContentOffsetTests: XCTestCase {
contentInset: measurementLayoutState.contentInset,
scale: measurementLayoutState.scale,
verticalLayoutDirection: measurementLayoutState.verticalLayoutDirection)
let id = layoutState.modelState.idForItemModel(at: IndexPath(item: 7, section: 0))!
XCTAssert(layoutState.targetContentOffsetAnchor == .topItem(id: id, distanceFromTop: -80))
let id = layoutState.modelState.idForItemModel(at: IndexPath(item: 9, section: 0))!
XCTAssert(layoutState.targetContentOffsetAnchor == .topItem(id: id, distanceFromTop: 25))
}

// MARK: Bottom-to-Top Anchor Tests
Expand All @@ -87,8 +87,8 @@ final class LayoutStateTargetContentOffsetTests: XCTestCase {
contentInset: UIEdgeInsets(top: 50, left: 0, bottom: 30, right: 0),
scale: 1,
verticalLayoutDirection: .bottomToTop)
let id = layoutState.modelState.idForItemModel(at: IndexPath(item: 12, section: 0))!
XCTAssert(layoutState.targetContentOffsetAnchor == .bottomItem(id: id, distanceFromBottom: 190))
let id = layoutState.modelState.idForItemModel(at: IndexPath(item: 10, section: 0))!
XCTAssert(layoutState.targetContentOffsetAnchor == .bottomItem(id: id, distanceFromBottom: -10))
}

func testAnchor_BottomToTop_ScrolledToBottom() throws {
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