UITraitCollection compatibility extension. under MIT license.

UITraitCollection+Compatible.swift

import UIKit

extension UITraitCollection {
	public var compatible: UITraitCollectionCompatible {
		return UITraitCollectionCompatible(self)
	}
}

public struct UITraitCollectionCompatible {
	private let traitCollection: UITraitCollection
	
	fileprivate init(_ traitCollection: UITraitCollection) {
		self.traitCollection = traitCollection
	}
	
	@available(iOS 9.0, *)
	public var preferredContentSizeCategory: UIContentSizeCategoryCompatible {
		let contentSizeCategory: UIContentSizeCategory
		if #available(iOS 10.0, *) {
			contentSizeCategory = traitCollection.preferredContentSizeCategory
		} else {
			contentSizeCategory = UITraitCollectionCompatible.getContentSizeCategory()
		}
		return UIContentSizeCategoryCompatible(contentSizeCategory)
	}
	
	private static func getContentSizeCategory() -> UIContentSizeCategory {
		let fontSize = UIFont.preferredFont(forTextStyle: .body).pointSize
		switch fontSize {
		case 14.0: return .extraSmall
		case 15.0: return .small
		case 16.0: return .medium
		case 17.0: return .large
		case 19.0: return .extraLarge
		case 21.0: return .extraExtraLarge
		case 23.0: return .extraExtraExtraLarge
		case 28.0: return .accessibilityMedium
		case 33.0: return .accessibilityLarge
		case 40.0: return .accessibilityExtraLarge
		case 47.0: return .accessibilityExtraExtraLarge
		case 53.0: return .accessibilityExtraExtraExtraLarge
		default: return .medium
		}
	}
}

@available(iOS 9.0, *)
public struct UIContentSizeCategoryCompatible {
	public let rawValue: UIContentSizeCategory
	
	fileprivate init(_ contentSizeCategory: UIContentSizeCategory) {
		self.rawValue = contentSizeCategory
	}
	
	public var isAccessibilityCategory: Bool {
		if #available(iOS 11.0, *) {
			return rawValue.isAccessibilityCategory
		} else {
			switch rawValue {
			case .accessibilityMedium: fallthrough
			case .accessibilityLarge: fallthrough
			case .accessibilityExtraLarge: fallthrough
			case .accessibilityExtraExtraLarge: fallthrough
			case .accessibilityExtraExtraExtraLarge:
				return true
				
			default:
				return false
			}
		}
	}
}

// MARK: - Equatable
extension UIContentSizeCategoryCompatible: Equatable {
	public static func == (lhs: UIContentSizeCategoryCompatible, rhs: UIContentSizeCategoryCompatible) -> Bool {
		return lhs.rawValue == rhs.rawValue
	}
}