最大行高截断文本

Question

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我想制作一个 pixelPerfect UI。我的设计师给了我一些特定字体的要求。我正在尝试实现它们，但我运行遇到了 paragraphStyle 的一些问题。所有文本优先基线必须位于网格上。将我的标题的 maximumLineHeight 设置为 24（2x 网格）时一切正常。但是，我的 bodyText 需要 lineHeight 为 16。这会切断第一行的顶部。

我试过设置标签高度，这只会增加布局冲突。我已经尝试将 firstBaseline 约束设置为远离其自身顶部的网格度量。无济于事。我还覆盖了 UILabel 的绘制方法以添加一些额外的顶部填充。但是，无论我添加什么填充，这都会在我的代码中使用 fristBaseline 约束。很脏，只有最后的最后手段。

import Foundation

public class UILabelBody: UILabel  {


    override public var text: String? {
        didSet {
            let attributedString = NSMutableAttributedString(string: self.text!)
            let paragraphStyle = NSMutableParagraphStyle()
            paragraphStyle.maximumLineHeight = 16

            attributedString.addAttributes([
                NSAttributedString.Key.kern: 0.4,
                NSAttributedString.Key.paragraphStyle : paragraphStyle],
                                           range: NSMakeRange(0, attributedString.length))
            self.attributedText = attributedString
        }
    }

    public init() {
        super.init(frame: CGRect.zero)
        self.translatesAutoresizingMaskIntoConstraints = false
        setup()
    }

    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

    private func setup() {
        self.font = UIFont(name: "Oxygen", size: 16)
        self.textColor = UIColor(hexString: "1F1F1F")
    }
}

这是我设置约束的class：私有函数设置（）{

    self.addSubview(contentBox)
    self.addSubview(imageView)
    self.addSubview(title)
    self.addSubview(body)


    imageView.backgroundColor = UIColor.yellow.withAlphaComponent(0.8)
    contentBox.backgroundColor = UIColor.red.withAlphaComponent(0.1)
    title.backgroundColor = UIColor.orange.withAlphaComponent(0.2)

    let padding = Layout.grid(1.5)

    let highPriority = UILayoutPriority(1000)
    let lowPrioririty = UILayoutPriority(100)

    let titleFirstBaseline = title.firstBaselineAnchor.constraint(equalTo: contentBox.topAnchor, constant: Layout.grid(2.5))
    let bodyFirstBaseLine =  body.firstBaselineAnchor.constraint(equalTo: title.lastBaselineAnchor, constant: Layout.grid(2))
    let selfHeight = self.heightAnchor.constraint(equalToConstant: Layout.grid(28))
    let selfWidth = self.widthAnchor.constraint(equalToConstant: Layout.grid(30))
    selfWidth.priority = highPriority
    selfHeight.priority = lowPrioririty

    titleFirstBaseline.priority = highPriority
    bodyFirstBaseLine.priority = highPriority


    NSLayoutConstraint.activate([


            selfWidth,
            selfHeight,

            contentBox.topAnchor.constraint(equalTo: self.topAnchor, constant: padding),
            contentBox.leadingAnchor.constraint(equalTo: self.leadingAnchor, constant: padding),
            contentBox.trailingAnchor.constraint(equalTo: self.trailingAnchor, constant: -padding),
            contentBox.bottomAnchor.constraint(equalTo: self.bottomAnchor, constant: -padding),

            imageView.leadingAnchor.constraint(equalTo: contentBox.leadingAnchor),
            imageView.topAnchor.constraint(equalTo: contentBox.topAnchor),
            imageView.widthAnchor.constraint(equalToConstant: Layout.grid(4)),
            imageView.heightAnchor.constraint(equalToConstant: Layout.grid(4)),

            title.leadingAnchor.constraint(equalTo: imageView.trailingAnchor, constant: padding),
            titleFirstBaseline,
            title.trailingAnchor.constraint(equalTo: self.trailingAnchor, constant: -padding),

            bodyFirstBaseLine,
            body.leadingAnchor.constraint(equalTo: self.leadingAnchor, constant: padding),
            body.bottomAnchor.constraint(equalTo: self.contentBox.bottomAnchor),
            body.trailingAnchor.constraint(equalTo: self.trailingAnchor, constant: -padding),
    ])
}

Answer 1

在刑讯室里待了几个小时后，我终于明白了！问题是字体本身。它是 .otf 而不是 .ttf。因为这个 swift 不理解字体的内部行高，就把它剪掉了。切换到 .ttf 后问题得到解决

最大行高截断文本

Maximum lineheight cutting off text

swift

nsparagraphstyle