SwiftUI sample showing different system font widths, including an undocumented extra expanded width

ContentView.swift

//
//  ContentView.swift
//  SystemFontWidths
//
//  Created by Geoff Hackworth on 27/01/2023.
//

import SwiftUI

struct ContentView: View {
    private let fontWidths: [Font.Width] = [.compressed, .condensed, .standard, .expanded, .extraExpanded]

    var body: some View {
        VStack(spacing: 8) {
            ForEach(fontWidths, id: \.self) { width in
                HStack(spacing: 8) {
                    Text("Hello, world!")
                        .frame(maxWidth: .infinity, alignment: .trailing)
                    Text("\(width.name)")
                        .frame(maxWidth: .infinity, alignment: .leading)
                }
                .fontWidth(width)
            }
        }
        .padding()
    }
}

extension Font.Width {

    /// Undocumented Font.Width
    static let extraExpanded = Font.Width(0.3)
}

private extension Font.Width {

    var name: String {
        let names: [Font.Width: String] = [
            .compressed: "compressed",
            .condensed: "condensed",
            .standard: "standard",
            .expanded: "expanded",
            .extraExpanded: "extraExpanded"
        ]

        return names[self] ?? "unknown"
    }
}

struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView()
    }
}