Fix line spacing in custom font in SwiftUI

Question

I am using custom font (Catamaran) and it seems like it has big space between lines in it. For example I have this code:

                Text("Example text that has big space between lines")
                    .lineSpacing(0)
                    .padding(.horizontal)
                    .font(Font.custom(FontNameManager.Catamaran.bold, size: 24.0))
                    .foregroundColor(.white)
                    .multilineTextAlignment(.center)

and it looks like this:

As you can see it doesn't have zero space between lines but it still gets too much space. I even tried to set negative numbers to lineSpacing method but it doesn't help. What can I do with this? How I can fix it? In UIKit I would probably use attributed string and I think I can use UILabel as UIViewRepresentable and then I can use attributed string in SwiftUI iOS 14. Is there some easier solution which can "fix" font for any usage? Do I have to edit original .ttf file? Why there is this space between lines in this font?

Thanks for any help

Answer 1

SwiftUI 可能使用hhea（水平标题表）的值来设置Text框高度。在您的例子中，双体船的上升高度为 1100，下降高度为 540。盒子高度将计算为这两个值的总和：540 + 1100 = 1640。字体的 UPM（Units per Em）默认为1000。这意味着在 SwiftUI 中，当.font(.custom(..., size: 1000))设置 时，每一行都Text()会有一个高度为1640的框架。

就 而言.lineSpacing()，SwiftUI 不设置基线之间的间距值，而是设置两个框之间的间距。如果您希望在下面的示例中两个框之间没有间距，不幸的是不允许设置.lineSpacing()为-(1640-1000) = -640（负值不可接受）。

更新：一种UIViewRepresentable方法

但是，您可以使用UILabel以下方法来减少行高：

struct CustomText: UIViewRepresentable {
    let text: String
    let font: UIFont
    
    func makeUIView(context: Context) -> UILabel {
        let label = UILabel()
        
        label.font = font
        label.numberOfLines = 0
        
        let attributedString = NSMutableAttributedString(string: text)
        let paragraphStyle = NSMutableParagraphStyle()
        paragraphStyle.lineHeightMultiple = 0.6  // <- Reduce lineHeight with a <1 factor
        
        attributedString.addAttribute(NSAttributedString.Key.paragraphStyle,
                                      value: paragraphStyle,
                                      range: NSMakeRange(0, attributedString.length))
        
        label.attributedText = attributedString
        
        return label
    }
    
    func updateUIView(_ uiView: UILabel, context: Context) { }
}

用法：

CustomText(text: "Foggy Days\nGo Nowhere",
           font: UIFont(name: "Catamaran", size: 1000)!)