I am trying to display RichText that comes in was HTML in my SwiftUI app. Following the instructions here with Hacking With Swift for parsing that HTML into a NSAttributedString.

This works great, except that when it get parsed into an attributed string it automatically gets TimesNewRoman and translates into 12pt.

I would like to make a few changes to it so that when it is displayed in my app it looks like it belongs:

1. Give it default system font.
2. Scale it up slightly. Body font is 14pt in our app.
3. Make it our text color.

So I embarked on making those changes which lead me to this wonderful solution listed here on Stack Overflow.

The problem is their solution relies on a bit of code where you need to run this line currentFont.fontDescriptor.addingAttributes([.family: "<Family Name>"])

First thing I tried was "San Francisco" but this did not work. I then used this other stack overflow post to get a list of font families. Unfortunately none of those families listed are San Francisco.

I then checked what this value was UIFont.systemFont(ofSize: 12, weight: .regular) curiously this returns a more primitive <UICTFont: 0x10900c7c0> font-family: ".SFUI-Regular"; font-weight: normal; font-style: normal; font-size: 20.00pt> object and if you ask it its .familyName you get .AppleSystemUIFont.

I tried plugging this all in with no luck. Here is the code I am trying and what it outputs to each step. It fails at the first if let.

That being said perhaps this is a sign to look at SwiftUI only solutions to this. As it would be nice to be able to modify the font from just regular SwiftUI modifiers. However I think since this attributed string has a font built in and the size/weight aspects of sections of the string are a part of a font I might be out of luck?

    // 
    let data = Data(html.utf8)
    if let rawAttributedString = try? NSMutableAttributedString(data: data, options: [.documentType: NSAttributedString.DocumentType.html], documentAttributes: nil) {
        let newAttributedString = rawAttributedString
        // 
        newAttributedString.enumerateAttribute(.font, in: NSMakeRange(0, newAttributedString.length), options: []) { value, range, stop in
            guard let currentFont = value as? UIFont else {
                return
            }
            let fontDescriptor = currentFont.fontDescriptor.addingAttributes([.family: ".AppleSystemUIFont", .name: ".SFUI-Regular"])
            /*
            UICTFontDescriptor <0x60000260edc0> = {
                NSCTFontVariationAttribute =     {
                    1869640570 = 12;
                    2003265652 = 400;
                    1936486004 = 0;
                    2003072104 = 100;
                };
                NSFontFamilyAttribute = ".AppleSystemUIFont";
                NSFontNameAttribute = ".SFUI-Regular";
                NSFontSizeAttribute = 12;
            }*/
            if let newFontDescriptor = fontDescriptor.matchingFontDescriptors(withMandatoryKeys: [.family]).first {
                // never gets here
                let newFont = UIFont(descriptor: newFontDescriptor, size: currentFont.pointSize * (14.0 / 12.0))
                newAttributedString.addAttributes([.font: newFont], range: range)
            }
        }
    }