Self-sizing cells with UICollectionViewCompositionalLayout - ios

Question

I have a view controller that displays a collection view with self-sizing cells. The collection view has one section that scrolls horizontally. It looks like this:
Problem
The collection view behaves unexpectedly when the view controller is presented using the default pageSheet style on iOS 13+.
When pulling upward on the sheet, cells may appear to resize like the cell labeled "Rectify" below:
When pulling upward on the sheet, the content may shift horizontally. Sometimes, cells may disappear too:
Question
Is there a way to fix this behavior while still using UICollectionViewCompositionalLayout and the pageSheet presentation style?
Code Summary
The code is pretty straightforward. Just 3 classes, which can be dropped into the ViewController.swift file using the Single View App project template in Xcode.
A UICollectionViewCell class called Cell. The cell has a UILabel and overrides sizeThatFits(_:).
A UIViewController called ViewController used only to present BugViewController.
BugViewController, which configures the data source and presents the collection view. This is where the problem occurs.
Code
import UIKit
// MARK: - Cell -
final class Cell: UICollectionViewCell {
static let reuseIdentifier = "Cell"
lazy var label: UILabel = {
let label = UILabel()
label.textAlignment = .center
label.frame.size = contentView.bounds.size
label.autoresizingMask = [.flexibleWidth, .flexibleHeight]
return label
}()
override init(frame: CGRect) {
super.init(frame: frame)
contentView.addSubview(label)
contentView.backgroundColor = .tertiarySystemFill
}
required init?(coder: NSCoder) {
fatalError("init(coder:) has not been implemented")
}
override func sizeThatFits(_ size: CGSize) -> CGSize {
.init(width: label.sizeThatFits(size).width + 32, height: 32)
}
}
// MARK: - ViewController -
final class ViewController: UIViewController {
private let button: UIButton = {
let button = UIButton(type: .system)
button.setTitle("Tap Me!".uppercased(), for: .normal)
button.addTarget(self, action: #selector(presentBugViewController), for: .touchUpInside)
button.sizeToFit()
return button
}()
override func viewDidLoad() {
super.viewDidLoad()
view.addSubview(button)
}
override func viewDidLayoutSubviews() {
super.viewDidLayoutSubviews()
button.center = view.center
}
#objc func presentBugViewController() {
present(BugViewController(), animated: true)
}
}
// MARK: - BugViewController -
final class BugViewController: UIViewController {
private let models = [
"Better Call Saul",
"Mad Men",
"Rectify",
"Tiger King: Murder, Mayhem, and Madness",
"Master of None",
"BoJack Horseman"
]
private lazy var collectionView: UICollectionView = {
let collectionView = UICollectionView(frame: view.bounds, collectionViewLayout: createCollectionViewLayout())
collectionView.register(Cell.self, forCellWithReuseIdentifier: Cell.reuseIdentifier)
collectionView.autoresizingMask = [.flexibleWidth, .flexibleHeight]
collectionView.contentInset.top = 44
collectionView.backgroundColor = .white
return collectionView
}()
private lazy var dataSource = UICollectionViewDiffableDataSource<Int, String>(collectionView: collectionView) { collectionView, indexPath, itemIdentifier in
guard let cell = collectionView.dequeueReusableCell(withReuseIdentifier: Cell.reuseIdentifier, for: indexPath) as? Cell else { fatalError() }
cell.label.text = itemIdentifier
return cell
}
override func viewDidLoad() {
super.viewDidLoad()
view.addSubview(collectionView)
var snapshot = NSDiffableDataSourceSnapshot<Int, String>()
snapshot.appendSections([0])
snapshot.appendItems(models)
dataSource.apply(snapshot)
}
private func createCollectionViewLayout() -> UICollectionViewCompositionalLayout {
let layoutSize = NSCollectionLayoutSize.init(
widthDimension: .estimated(200),
heightDimension: .absolute(32)
)
let section = NSCollectionLayoutSection(group:
.horizontal(
layoutSize: layoutSize,
subitems: [.init(layoutSize: layoutSize)]
)
)
section.interGroupSpacing = 8
section.orthogonalScrollingBehavior = .continuous
return .init(section: section)
}
}
Notes
The collection view in my app actually has many sections and scrolls vertically. That is why I'm using a vertically scrolling collection view and a section with orthogonalScrollingBehavior in the example code.
Failed Attempts
I've tried using Auto Layout constraints instead of sizeThatFits(_:).
I've tried not using UICollectionViewDiffableDataSource.
Workarounds
Modifying the cell with a child scroll view and passing in an array of strings (as opposed to one at a time) does avoid this problem. But, it's a dirty hack that I'd like to avoid if possible.