Question

我正在使用New Font Features at WWDC 2015中的优秀代码：

import UIKit

let pointSize : CGFloat = 60.0
let systemFontDesc = UIFont.systemFont(ofSize: pointSize,
                                             weight: UIFontWeightLight).fontDescriptor
let fractionFontDesc = systemFontDesc.addingAttributes(
    [
        UIFontDescriptorFeatureSettingsAttribute: [
            [
                UIFontFeatureTypeIdentifierKey: kFractionsType,
                UIFontFeatureSelectorIdentifierKey: kDiagonalFractionsSelector,
                ],
        ]
    ] )

let label = UILabel(frame: CGRect(x: 0, y: 0, width: 200, height: 100))

label.font = UIFont(descriptor: fractionFontDesc, size:pointSize)
label.text = "12/48"

WWDC视频显示了UIFontDescriptorFeatureSettingsAttribute的其他用途，例如上级（e =mc²）

但解锁其他属性的关键是什么？

UIFontDescriptorFeatureSettingsAttribute的文档页面只是说它是一个包含UIFontFeatureTypeIdentifierKey和UIFontFeatureSelectorIdentifierKey的字典数组。

这两个密钥（type和selector）的文档只是说它们是NSNumber。

对于分数，type为kFractionsType，selector为kDiagonalFractionsSelector

如何找到其他可用功能的密钥？

Answer 1

Core Text将为您列出字体的隐藏功能：

let desc = UIFontDescriptor(name: "Didot", size: 20) as CTFontDescriptor
let f = CTFontCreateWithFontDescriptor(desc,0,nil)
let arr = CTFontCopyFeatures(f)
print(arr as Any)

对于具有魔术名称的功能，您必须查看 SFNTLayoutTypes.h 标题。

如何找到UIFontFeatureTypeIdentifierKey的不同键？

1 个答案: