Custom Dynamic Font for SwiftUI

FontsSwiftUI.swift

//
//  CustomFont.swift
//  BLNC
//
//  Created by Egor Merkushev on 31.05.2021.
//  Copyright © 2021 Egor Merkushev. All rights reserved.
//  Source: https://stackoverflow.com/a/58971579/602249

import SwiftUI

extension View {
    func customFont(_ textStyle: UIFont.TextStyle) -> ModifiedContent<Self, CustomFont> {
        return modifier(CustomFont(textStyle: textStyle))
    }
}

struct CustomFont: ViewModifier {
    let textStyle: UIFont.TextStyle

    /// Will trigger the refresh of the view when the ContentSizeCategory changes.
    @Environment(\.sizeCategory) var sizeCategory: ContentSizeCategory

    func body(content: Content) -> some View {

        guard let fontDescription = fontDescriptions[textStyle] else {
            return content.font(.system(.body));
        }

        let fontMetrics = UIFontMetrics(forTextStyle: textStyle)
        let fontSize = fontMetrics.scaledValue(for: fontDescription.0)

        return content.font(.system(size: fontSize, weight: fontDescription.1, design: .rounded))
    }
}

/// Define the custom fonts to use, depending on the TextStyle.
typealias CustomFontDescription = (CGFloat, Font.Weight)
private var fontDescriptions: [UIFont.TextStyle: CustomFontDescription] = [
    .headline: (17, .semibold),
    .subheadline: (15, .regular),
    .largeTitle: (34.0, .regular),
    .title1: (28, .regular),
    .title2: (22.0, .regular),
    .title3: (20.0, .regular),
    .callout: (16.0, .regular),
    .body: (17.0, .regular),
    .footnote: (13.0, .regular),
    .caption1: (12.0, .regular),
    .caption2: (11.0, .regular)
]

@available(iOS 13, macCatalyst 13, tvOS 13, watchOS 6, *)
struct ScaledFont: ViewModifier {
    @Environment(\.sizeCategory) var sizeCategory
    var name: String
    var size: CGFloat

    func body(content: Content) -> some View {
       let scaledSize = UIFontMetrics.default.scaledValue(for: size)
        return content.font(.custom(name, size: scaledSize))
    }
}

@available(iOS 13, macCatalyst 13, tvOS 13, watchOS 6, *)
extension View {
    func scaledFont(name: String, size: CGFloat) -> some View {
        return self.modifier(ScaledFont(name: name, size: size))
    }
}