byre/mac/Sources/Byre/Fonts.swift

import CoreText
import SwiftUI

enum Fonts {
    nonisolated(unsafe) private static let descriptors: [String: CTFontDescriptor] = {
        let dir = Bundle.main.resourceURL!.appendingPathComponent("fonts")
        var out: [String: CTFontDescriptor] = [:]
        for name in try! FileManager.default.contentsOfDirectory(atPath: dir.path) where name.hasSuffix(".woff2") {
            let url = dir.appendingPathComponent(name)
            let found = CTFontManagerCreateFontDescriptorsFromURL(url as CFURL) as! [CTFontDescriptor]
            out[name] = found[0]
        }
        return out
    }()

    private static func file(_ subset: String, _ italic: Bool, _ weight: CGFloat) -> CTFontDescriptor {
        let d = descriptors["atkinson-hyperlegible-mono-\(subset)-wght-\(italic ? "italic" : "normal").woff2"]!
        return CTFontDescriptorCreateCopyWithVariation(d, 0x7767_6874 as CFNumber, weight)
    }

    static func ct(_ size: CGFloat, weight: CGFloat = 400, italic: Bool = false) -> CTFont {
        let ext = file("latin-ext", italic, weight)
        let d = CTFontDescriptorCreateCopyWithAttributes(file("latin", italic, weight), [kCTFontCascadeListAttribute: [ext]] as CFDictionary)
        return CTFontCreateWithFontDescriptor(d, size, nil)
    }

    nonisolated(unsafe) private static var fonts: [String: Font] = [:]
    private static let lock = NSLock()

    static func font(_ size: CGFloat, weight: CGFloat = 400, italic: Bool = false) -> Font {
        let key = "\(size) \(weight) \(italic)"
        lock.lock()
        defer {
            lock.unlock()
        }
        if let f = fonts[key] {
            return f
        }
        let f = Font(ct(size, weight: weight, italic: italic))
        fonts[key] = f
        return f
    }
}