How to set a custom font family as the default for an entire app in SwiftUI

Question

In SwiftUI you get all these handy little Font convenience accessors like Font.caption, Font.title, Font.body, etc..

e.g.

VStack {
 Text("Some Title").font(Font.title)
 Text("Some Caption Text").font(Font.caption)
}

They all specify different font styles for the default Helvetica font family. I'd like to use these very helpful convenience accessors without ever using Helvetica in my app. Can I change the default font family? Or do I constantly have to apply custom fonts like e.g.:

Text("Custom Text").font(Font.custom("SourceSansPro-Regular", size: 14.0)

Answer 1

You can override the system font if you want.

    extension Font {
    
    /// Create a font with the large title text style.
    public static var largeTitle: Font {
        return Font.custom("OpenSans-Regular", size: UIFont.preferredFont(forTextStyle: .largeTitle).pointSize)
    }

    /// Create a font with the title text style.
    public static var title: Font {
        return Font.custom("OpenSans-Regular", size: UIFont.preferredFont(forTextStyle: .title1).pointSize)
    }

    /// Create a font with the headline text style.
    public static var headline: Font {
        return Font.custom("OpenSans-Regular", size: UIFont.preferredFont(forTextStyle: .headline).pointSize)
    }

    /// Create a font with the subheadline text style.
    public static var subheadline: Font {
        return Font.custom("OpenSans-Light", size: UIFont.preferredFont(forTextStyle: .subheadline).pointSize)
    }

    /// Create a font with the body text style.
    public static var body: Font {
           return Font.custom("OpenSans-Regular", size: UIFont.preferredFont(forTextStyle: .body).pointSize)
       }

    /// Create a font with the callout text style.
    public static var callout: Font {
           return Font.custom("OpenSans-Regular", size: UIFont.preferredFont(forTextStyle: .callout).pointSize)
       }

    /// Create a font with the footnote text style.
    public static var footnote: Font {
           return Font.custom("OpenSans-Regular", size: UIFont.preferredFont(forTextStyle: .footnote).pointSize)
       }

    /// Create a font with the caption text style.
    public static var caption: Font {
           return Font.custom("OpenSans-Regular", size: UIFont.preferredFont(forTextStyle: .caption1).pointSize)
       }

    public static func system(size: CGFloat, weight: Font.Weight = .regular, design: Font.Design = .default) -> Font {
        var font = "OpenSans-Regular"
        switch weight {
        case .bold: font = "OpenSans-Bold"
        case .heavy: font = "OpenSans-ExtraBold"
        case .light: font = "OpenSans-Light"
        case .medium: font = "OpenSans-Regular"
        case .semibold: font = "OpenSans-SemiBold"
        case .thin: font = "OpenSans-Light"
        case .ultraLight: font = "OpenSans-Light"
        default: break
        }
        return Font.custom(font, size: size)
    }
}