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

这将生成带有可变宽度字符的文本.我需要获得一个monospace字体,而不需要硬编码快递新的和固定的大小.部署目标是ios 9.0

Answer 1

这是一个扩展，UIFontDescriptor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或获得完全等宽的字体UIFontDescriptor。此解决方案尝试找到良好的等宽字体，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
    }
}

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

使用示例：

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

以下是一些测试代码，用于确认preferredMonoFontDescriptor(withTextStyle:)所有样式的结果都能正常工作：

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)
}

如果比较每对结果，它们具有相同的大小、粗细和样式，只是字体不同。