【Swift】NSParagraphStyleで自在にレイアウト①

import UIKit
import PlaygroundSupport

class ViewController: UIViewController {

    weak var textView: UITextView!

    override func loadView() {

        let view = UIView()
        view.backgroundColor = .systemBackground
        self.view = view

        // Create a UITextView
        let textView = UITextView()
        view.addSubview(textView)
        textView.translatesAutoresizingMaskIntoConstraints = false
        textView.leadingAnchor.constraint(equalTo: view.leadingAnchor, constant: 10).isActive = true
        textView.trailingAnchor.constraint(equalTo: view.trailingAnchor, constant: -10).isActive = true
        textView.topAnchor.constraint(equalTo: view.topAnchor, constant: 10).isActive = true
        textView.bottomAnchor.constraint(equalTo: view.bottomAnchor, constant: -10).isActive = true
        textView.isEditable = false
        textView.isSelectable = true
        self.textView = textView

        test()
    }

    func test() {
//        testLineHeightAndSpacing()
//        testParagraphSpacing()
//        testIndent()
//        testAlignment()
//        testBaseWritingDirection()
//        testBaseWritingDirection2()
//        testLineBreakMode()
//        testLineBreakStrategy1()
//        testLineBreakStrategy2()
//        testLineBreakStrategy3()
//        testHyphenationFactor()
//        testAllowsDefaultTighteningForTruncation()
//        testTabStops()
    }
}

extension NSTextAlignment: CustomStringConvertible {

    public var description: String {
        switch self {
            case .left: return "left"
            case .center: return "center"
            case .right: return "right"
            case .justified: return "justified"
            case .natural: return "natural"
        }
    }
}

extension NSWritingDirection: CustomStringConvertible {

    public var description: String {
        switch self {
            case .natural: return "natural"
            case .leftToRight: return "leftToRight"
            case .rightToLeft: return "rightToLeft"
        }
    }
}

extension NSWritingDirectionFormatType: CustomStringConvertible {

    public var description: String {
        switch self {
            case .embedding: return "embedding"
            case .override: return "override"
        }
    }
}

extension NSLineBreakMode: CustomStringConvertible {

    public var description: String {
        switch self {
            case .byWordWrapping: return "byWordWrapping"
            case .byCharWrapping: return "byCharWrapping"
            case .byClipping: return "byClipping"
            case .byTruncatingHead: return "byTruncatingHead"
            case .byTruncatingTail: return "byTruncatingTail"
            case .byTruncatingMiddle: return "byTruncatingMiddle"
        }
    }
}

PlaygroundPage.current.liveView = ViewController()

func testLineHeightAndSpacing() {

    let string = NSMutableAttributedString()

    if let image = UIImage(named: "monogatari_oz") {
        let attachment = NSTextAttachment()
        attachment.image = image
        attachment.bounds = CGRect(x: 0, y: 0, width: 60, height: 40)

        string.append(NSAttributedString(attachment: attachment))
    }

    string.append(NSAttributedString(string: "Dorothy lived in the midst of the great Kansas prairies, with Uncle Henry, who was a farmer, and Aunt Em, who was the farmer's wife."))

    let style = NSMutableParagraphStyle()
    //style.lineHeightMultiple = 2.0
    //style.minimumLineHeight = 30.0
    //style.maximumLineHeight = 50.0
    //style.lineSpacing = 20.0

    string.addAttributes([
        .paragraphStyle: style,
        .backgroundColor: UIColor(white: 0.8, alpha: 1.0),
    ], range: NSRange(0..<string.length))

    textView.attributedText = string
}

style.lineHeightMultiple = 2.0

style.minimumLineHeight = 30.0

style.lineHeightMultiple = 2.0
style.maximumLineHeight = 50.0

style.lineSpacing = 20.0

func testParagraphSpacing() {

    let CR = "\r"
    let LF = "\n"
    let paragraphSeparator = "\u{2029}"
    let lineSeparator = "\u{2028}"
    let backgroundColor1 = UIColor(white: 0.8, alpha: 1.0)
    let backgroundColor2 = UIColor.green.withAlphaComponent(0.2)

    let string = NSMutableAttributedString()

    string.append(NSAttributedString(string: "Dorothy lived in the midst of the great Kansas prairies,", attributes: [.backgroundColor: backgroundColor1]))
    string.append(NSAttributedString(string: "\(CR)with Uncle Henry,", attributes: [.backgroundColor: backgroundColor2]))
    string.append(NSAttributedString(string: "\(LF)who was a farmer,", attributes: [.backgroundColor: backgroundColor1]))
    string.append(NSAttributedString(string: "\(CR)\(LF)and Aunt Em,", attributes: [.backgroundColor: backgroundColor2]))
    string.append(NSAttributedString(string: "\(paragraphSeparator)who was", attributes: [.backgroundColor: backgroundColor1]))
    string.append(NSAttributedString(string: "\(lineSeparator)the farmer's wife.", attributes: [.backgroundColor: backgroundColor2]))

    let style = NSMutableParagraphStyle()
    //style.paragraphSpacing = 10
    //style.paragraphSpacingBefore = 10

    string.addAttributes([
        .paragraphStyle: style,
    ], range: NSRange(0..<string.length))

    textView.attributedText = string
}

style.paragraphSpacing = 10

style.paragraphSpacingBefore = 10

func testIndent() {

    let string = NSMutableAttributedString()

    if let image = UIImage(named: "monogatari_oz") {
        let attachment = NSTextAttachment()
        attachment.image = image
        attachment.bounds = CGRect(x: 0, y: 0, width: 60, height: 40)

        string.append(NSAttributedString(attachment: attachment))
    }

    string.append(NSAttributedString(string: "Dorothy lived in the midst of the great Kansas prairies, with Uncle Henry, who was a farmer, and Aunt Em, who was the farmer's wife.\n\nTheir house was small, for the lumber to build it had to be carried by wagon many miles."))

    let style = NSMutableParagraphStyle()
    style.firstLineHeadIndent = 20
    style.headIndent = 10
    style.tailIndent = 300

    string.addAttributes([
        .paragraphStyle: style,
        .backgroundColor: UIColor(white: 0.8, alpha: 1.0),
    ], range: NSRange(0..<string.length))

    textView.attributedText = string
    textView.backgroundColor = UIColor.green.withAlphaComponent(0.2)
}

style.tailIndent = -20

func testAlignment() {

    let string = NSMutableAttributedString()

    [NSTextAlignment.natural, .left, .right, .center, .justified].forEach { alignment in

        string.append(NSAttributedString(string: "\(alignment)\n", attributes: [
            .font: UIFont.systemFont(ofSize: 14, weight: .heavy),
            .foregroundColor: UIColor.red,
        ]))

        let style = NSMutableParagraphStyle()
        style.alignment = alignment

        string.append(NSAttributedString(string: "Dorothy lived in the midst of the great Kansas prairies, with Uncle Henry, who was a farmer, and Aunt Em, who was the farmer's wife.", attributes: [
            .paragraphStyle: style,
            .backgroundColor: UIColor(white: 0.8, alpha: 1.0),
        ]))

        string.append(NSAttributedString(string: "\n\n"))
    }

    textView.attributedText = string
}

func testBaseWritingDirection() {

    let arabicHello = "أهلا"
    let englishHello = "Hello"

    let string = NSMutableAttributedString()

    [NSWritingDirection.natural, .leftToRight, .rightToLeft].forEach { direction in

        // Title
        string.append(NSAttributedString(string: "\(direction)\n", attributes: [
            .font: UIFont.systemFont(ofSize: 14, weight: .heavy),
            .foregroundColor: UIColor.red,
        ]))

        let style = NSMutableParagraphStyle()
        style.baseWritingDirection = direction

        // Arabian first, English second
        string.append(NSAttributedString(string: "😃 \(arabicHello) \(englishHello)", attributes: [
            .paragraphStyle: style,
            .backgroundColor: UIColor(white: 0.8, alpha: 1.0),
        ]))

        string.append(NSAttributedString(string: "\n"))

        // English first, Arabian second
        string.append(NSAttributedString(string: "😃 \(englishHello) \(arabicHello)", attributes: [
            .paragraphStyle: style,
            .backgroundColor: UIColor(white: 0.8, alpha: 1.0),
        ]))

        string.append(NSAttributedString(string: "\n\n"))
    }

    textView.attributedText = string
}

func testBaseWritingDirection2() {

    let arabicHello = "أهلا"
    let englishHello = "Hello"

    let string = NSMutableAttributedString()

    [NSWritingDirection.natural, .leftToRight, .rightToLeft].forEach { baseDirection in
        [NSWritingDirection.natural, .leftToRight, .rightToLeft].forEach { direction in
            [NSWritingDirectionFormatType.embedding, .override].forEach { type in

                // Title
                let title = "base-\(baseDirection) + \(direction) + \(type)"
                string.append(NSAttributedString(string: "\(title)\n", attributes: [
                    .font: UIFont.systemFont(ofSize: 14, weight: .heavy),
                    .foregroundColor: UIColor.red,
                ]))

                let style = NSMutableParagraphStyle()
                style.baseWritingDirection = baseDirection

                // Arabian first, English second
                string.append(NSAttributedString(string: "😃 \(arabicHello) \(englishHello)", attributes: [
                    .paragraphStyle: style,
                    .backgroundColor: UIColor(white: 0.8, alpha: 1.0),
                    .writingDirection: [direction.rawValue | type.rawValue],
                ]))

                string.append(NSAttributedString(string: "\n"))

                // English first, Arabian second
                string.append(NSAttributedString(string: "😃 \(englishHello) \(arabicHello)", attributes: [
                    .paragraphStyle: style,
                    .backgroundColor: UIColor(white: 0.8, alpha: 1.0),
                    .writingDirection: [direction.rawValue | type.rawValue],
                ]))

                string.append(NSAttributedString(string: "\n\n"))
            }
        }
    }

    textView.attributedText = string
}