如何获得尊重可访问性设置的等宽字体

Question

let bodyFontDescriptor = UIFontDescriptor
    .preferredFontDescriptor(withTextStyle: UIFontTextStyle.body)
let bodyMonospacedFontDescriptor = bodyFontDescriptor.addingAttributes(
    [
        UIFontDescriptorFeatureSettingsAttribute: [
            [
                UIFontFeatureTypeIdentifierKey: kTextSpacingType,
                UIFontFeatureSelectorIdentifierKey: kMonospacedTextSelector
            ]
        ]
    ])
let bodyMonospacedFont = UIFont(descriptor: bodyMonospacedFontDescriptor, size: 0.0)
textview.font = bodyMonospacedFont

这会产生具有可变宽度字符的文本。 我需要在没有硬编码 courier new 的情况下获得等宽字体 和固定大小。 部署目标是 ios 9.0

Answer 1

这是UIFontDescriptor 的扩展，它返回给定文本样式的首选等宽字体描述符。没有简单的方法可以使用UIFont 或UIFontDescriptor 获得完全等宽字体。此解决方案试图找到一个好的等宽字体，并在需要时回退到 Courier。

extension UIFontDescriptor {
    static let monoDescriptor: UIFontDescriptor = {
        // Attempt to find a good monospaced, non-bold, non-italic font
        for family in UIFont.familyNames {
            for name in UIFont.fontNames(forFamilyName: family) {
                let f = UIFont(name: name, size: 12)!
                let fd = f.fontDescriptor
                let st = fd.symbolicTraits
                if st.contains(.traitMonoSpace) && !st.contains(.traitBold) && !st.contains(.traitItalic) && !st.contains(.traitExpanded) && !st.contains(.traitCondensed) {
                    return fd
                }
            }
        }

        return UIFontDescriptor(name: "Courier", size: 0) // fallback
    }()

    class func preferredMonoFontDescriptor(withTextStyle style: UIFontTextStyle) -> UIFontDescriptor {
        // Use the following line if you need a fully monospaced font
        let monoDescriptor = UIFontDescriptor.monoDescriptor

        // Use the following two lines if you only need monospaced digits in the font
        //let monoDigitFont = UIFont.monospacedDigitSystemFont(ofSize: 0, weight: .regular)
        //let monoDescriptor = monoDigitFont.fontDescriptor

        // Get the non-monospaced preferred font
        let defaultFontDescriptor = preferredFontDescriptor(withTextStyle: style)
        // Remove any attributes that specify a font family or name and remove the usage
        // This will leave other attributes such as size and weight, etc.
        var fontAttrs = defaultFontDescriptor.fontAttributes
        fontAttrs.removeValue(forKey: .family)
        fontAttrs.removeValue(forKey: .name)
        fontAttrs.removeValue(forKey: .init(rawValue: "NSCTFontUIUsageAttribute"))
        let monospacedFontDescriptor = monoDescriptor.addingAttributes(fontAttrs)

        return monospacedFontDescriptor.withSymbolicTraits(defaultFontDescriptor.symbolicTraits) ?? monospacedFontDescriptor
    }
}

请注意 cmets 是否需要完全等宽的字体或仅具有等宽数字的字体。注释/取消注释这些行以满足您的特定需求。

示例用法：

let bodyMonospacedFont = UIFont(descriptor: .preferredMonoFontDescriptor(withTextStyle: .body), size: 0)
textview.font = bodyMonospacedFont

以下是一些测试代码，以确认preferredMonoFontDescriptor(withTextStyle:) 的结果适用于所有样式：

let textStyles: [UIFontTextStyle] = [ .body, .callout, .caption1, .caption2, .footnote, .headline, .subheadline, .largeTitle, .title1, .title2, .title3 ]
for style in textStyles {
    let nfont = UIFont(descriptor: .preferredFontDescriptor(withTextStyle: style), size: 0)
    let mfont = UIFont(descriptor: .preferredMonoFontDescriptor(withTextStyle: style), size: 0)
    print(style)
    print(nfont)
    print(mfont)
}

如果您比较每对结果，它们的大小、重量和样式都相同，只是字体不同。