FontManager+AutoScaleSettings.swift

// somewhere here is a declaration of the Font Style parts
// https://gist.github.com/popcornomnom/5288be0c003fedff3e9d43c332837dca
// and func stringName(_, _) -> String
// https://gist.github.com/popcornomnom/1238714fea8d9a8efa109782958a5b99

///optional type in case if you don't want to support scaled font yet
private let autoScaleSettings: AutoScaleSettings? = AutoScaleSettings()

private class AutoScaleSettings {
    let mostPopularScreenWidth: CGFloat = 375
    let maxScreenWidth: CGFloat = 460 //use to prevent huge font scaling on iPad
    let minScaleFactor: CGFloat = 0.93 //to protect scalling of very small sizes
}

extension UIFont {
    
    convenience init(_ family: Family = .defaultFamily,
                     _ size: Size, _ weight: CustomWeight) {
        var size = size.rawValue
        if let autoScaleSettings = autoScaleSettings {
            var ratio = (min(UIScreen.main.bounds.width, autoScaleSettings.maxScreenWidth)
                / autoScaleSettings.mostPopularScreenWidth)
            ratio = max(autoScaleSettings.minScaleFactor, ratio)
            if ratio > 1 || (ratio < 1 && size.doesSupportMinScalling) {
                _size = round(ratio * _size)
            }
        }
        self.init(name: stringName(family, weight), size: size)!
    }
}