A Swift modifier to get the monospaced high legibility figures

Font+HighLegibilityFigures.swift

import UIKit
import SwiftUI

extension View {
    func highLegibilityFigures(forStyle style: UIFont.TextStyle, tableFigures: Bool = false) -> some View {
        modifier(HighLegibilityFigures(style: style, tableFigures: tableFigures))
    }
}

private struct HighLegibilityFigures: ViewModifier {

    var style: UIFont.TextStyle = .body
    var tableFigures: Bool = false

    func body(content: Content) -> some View {
        content
            .font(HighLegibilityFigures.highLegibilityForStyle(style, tableFigures: tableFigures))
    }

    static func highLegibilityForStyle(_ style: UIFont.TextStyle, tableFigures: Bool) -> Font {

        var attributes = [
            UIFontDescriptor.AttributeName.featureSettings: [
                [   // High legibility 6 and 9
                    UIFontDescriptor.FeatureKey.type: kStylisticAlternativesType,
                    UIFontDescriptor.FeatureKey.selector: kStylisticAltOneOnSelector
                ],
                [   // High legibility 4
                    UIFontDescriptor.FeatureKey.type: kStylisticAlternativesType,
                    UIFontDescriptor.FeatureKey.selector: kStylisticAltTwoOnSelector
                ]
            ]
        ]

        if tableFigures {
            attributes[UIFontDescriptor.AttributeName.featureSettings]?.append(
                [
                    UIFontDescriptor.FeatureKey.type: kNumberSpacingType,
                    UIFontDescriptor.FeatureKey.selector: kMonospacedNumbersSelector
                ]
            )
        }

        let fontDescriptor = UIFontDescriptor.preferredFontDescriptor(withTextStyle: style)
        let descriptor = fontDescriptor.addingAttributes(attributes)

        let fontSize = fontDescriptor.pointSize

        let uiFont = UIFont(descriptor: descriptor, size: fontSize)
        let swiftUIFont = Font(uiFont)

        return swiftUIFont
    }
}