Swift 如何让CTFontCreateUIFontForLanguage与汉字和表情包协同工作

这个问题与CoreText(在苹果平台上可用)有关.语言是Swift 5.10.

如果给定的UniChar数组包含汉字/表情符号，则CTFontCreateUIFontForLanguage()似乎不会返回可用的结果.

我的try :

假设我使用以下SWIFT脚本使用CTFontCreateUIFontForLanguage().

#!/usr/bin/env swift

import CoreText
import Foundation

guard let osFont = CTFontCreateUIFontForLanguage(
  .system, 14, "zh-Hant" as CFString
) else {
  print("CTFont initiation failed.")
  exit(1) // Abortion.
}

extension CTFont {
  func glyphs(for string: String) -> [CGGlyph]? {
    let arrUTF16 = Array(string.utf16)
    var glyphs = [CGGlyph](repeating: 0, count: arrUTF16.count)
    let result = CTFontGetGlyphsForCharacters(self, arrUTF16, &glyphs, arrUTF16.count)
    return result ? glyphs : nil
  }
}

let string = "這是草莓蛋糕🍓🍰." // NOTE: Edit this line to try various parameters.
let unichars = Array(string.utf16)

var fetchedGlyphs: [CGGlyph]? = osFont.glyphs(for: string)
guard var fetchedGlyphs = fetchedGlyphs else {
  print("Screwed. I don't know why it only works with ASCII glyphs.")
  exit(1) // Abortion.
}

请注意，CTFont可以替换为NSFont.systemFont(ofSize: NSFont.systemFontSize)，而不是我在上面创建的字体.CTFont和NSFont在SWIFT 5中是免费桥接的.

此案的问题在于:

如果给定的字符串参数包含汉字和/或表情字符，则(CTFont instance).glyphs(for:)返回nil.可以try 使用其他仅支持汉字的字符串或仅支持表情符号的字符串.