swift-calendar-view-layout.swift

var itemsPerRow: CGFloat = 3

func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
	guard let flow = collectionViewLayout as? UICollectionViewFlowLayout else {
		fatalError("only flow layout is supported")
	}

	let paddingSpace = flow.sectionInset.left + flow.sectionInset.right + (minimumInteritemSpacing * itemsPerRow)
	let availableWidth = collectionView.frame.width - paddingSpace
	let widthPerItem = availableWidth / itemsPerRow

	return CGSize(width: widthPerItem, height: widthPerItem)
}

func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, insetForSectionAt section: Int) -> UIEdgeInsets {
	guard let flow = collectionViewLayout as? UICollectionViewFlowLayout else {
		fatalError("only flow layout is supported")
	}

	return flow.sectionInset
}