byre/mac/Sources/Byre/Fonts.swift

import CoreText
import Synchronization
import SwiftUI

enum Fonts {
    private static func file(_ subset: String, _ italic: Bool, _ weight: CGFloat) -> CTFontDescriptor {
        let url = Bundle.main.resourceURL!.appending(path: "fonts/atkinson-hyperlegible-mono-\(subset)-wght-\(italic ? "italic" : "normal").woff2")
        let d = (CTFontManagerCreateFontDescriptorsFromURL(url as CFURL) as! [CTFontDescriptor])[0]
        return CTFontDescriptorCreateCopyWithVariation(d, 0x7767_6874 as CFNumber, weight)
    }

    private 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)
    }

    private static let fonts = Mutex<[String: CTFont]>([:])

    private static func cached(_ size: CGFloat, _ weight: CGFloat, _ italic: Bool) -> CTFont {
        let key = "\(size) \(weight) \(italic)"
        return fonts.withLock { fonts in
            if let f = fonts[key] {
                return f
            }
            let f = ct(size, weight: weight, italic: italic)
            fonts[key] = f
            return f
        }
    }

    static func font(_ size: CGFloat, weight: CGFloat = 400, italic: Bool = false) -> Font {
        Font(cached(size, weight, italic))
    }

    static func ns(_ size: CGFloat, weight: CGFloat = 400, italic: Bool = false) -> NSFont {
        cached(size, weight, italic) as NSFont
    }
}