NSString.getRenderedDimension().

String-getRenderedDimension.swift

// (c) 2022 and onwards The vChewing Project (MIT-NTL License).
// ====================
// This code is released under the MIT license (SPDX-License-Identifier: MIT)
// ... with NTL restriction stating that:
// No trademark license is granted to use the trade names, trademarks, service
// marks, or product names of Contributor, except as required to fulfill notice
// requirements defined in MIT License.

import CoreText
import Foundation

public extension String {
  func getRenderedDimension(
    using givenFont: CTFont? = nil,
    size: CGFloat? = 13, /* NSFont.systemFontSize defaults to 13. */
    orientation: CTFontOrientation = .horizontal,
    locale localeIdentifier: String? = nil
  ) -> CGSize {
    let size = size ?? 13
    let baseFont = givenFont ?? CTFont(.system, size: size)
    func createMatchedFont(char: Character) -> CTFont {
      var cfLocaleIdentifier: CFString?
      if let localeIdentifier = localeIdentifier {
        cfLocaleIdentifier = localeIdentifier as CFString
      }
      return CTFontCreateForStringWithLanguage(
        baseFont,
        char.description as CFString,
        CFRange(location: 0, length: char.utf16.count),
        cfLocaleIdentifier
      )
    }
    let emojiFallbackSize = size * 1.25
    var finalWidth: CGFloat = 0
    var finalHeight: CGFloat = 0
    switch orientation {
    case .horizontal: finalHeight = emojiFallbackSize
    case .vertical: finalWidth = emojiFallbackSize
    default: break
    }
    forEach { char in
      let uniChars = Array(char.utf16)
      let matchedFont = createMatchedFont(char: char)
      // The subCount needs to be 1, considering that this is the only literal scalar amount to show.
      // Otherwise, incorrect results will be generated while parsing NFD compositions.
      let subCount = 1
      var fetchedGlyphs = [CGGlyph](repeating: 0, count: subCount)
      let result = CTFontGetGlyphsForCharacters(matchedFont, uniChars, &fetchedGlyphs, subCount)
      guard result, !fetchedGlyphs.isEmpty else {
        switch orientation {
        case .horizontal: finalWidth += emojiFallbackSize
        case .vertical: finalHeight += emojiFallbackSize
        default: break
        }
        return
      }
      let advance = CTFontGetAdvancesForGlyphs(matchedFont, orientation, fetchedGlyphs, nil, subCount)
      switch orientation {
      case .horizontal: finalWidth += advance
      case .vertical: finalHeight += advance
      default: break
      }
    }
    return .init(width: ceil(finalWidth), height: ceil(finalHeight))
  }
}