Creating an italic version from a light font using symbolic traits

Question

I'd like to get an italic version of a light font, for example "HelveticaNeue-Light".

Using a fontDescriptor gives me the italic version of the 'regular' "Helvetica Neue" instead of the italic "HelveticaNeue-Light". I could retrieve the fontDescriptor.fontAttributes and update the UIFontDescriptor.AttributeName.name, but that's tricky, because the naming is different per font ("HelveticaNeue" uses "Italic", Helvetica uses "Oblique").

let lightFont = UIFont(name: "HelveticaNeue-Light", size: 16.0)!
var lightFontDescriptor = lightFont.fontDescriptor.withSymbolicTraits([.traitItalic])!
var lightFontWithItalicTraits = UIFont(descriptor: lightFontDescriptor, size: 0)

// <UICTFont: ..> font-family: "HelveticaNeue-Light"; font-weight: normal; font-style: normal; font-size: 16.00pt
print(lightFont)

// <UICTFont: ..> font-family: "Helvetica Neue"; font-weight: normal; font-style: italic; font-size: 16.00pt
print(lightFontWithItalicTraits)

// The font I expect:
let lightItalicFont = UIFont(name: "HelveticaNeue-LightItalic", size: 16.0)!
// <UICTFont: ..> font-family: "HelveticaNeue-LightItalic"; font-weight: normal; font-style: italic; font-size: 16.00pt
print(lightItalicFont)

Any other idea how to get the italic version of an existing font?

elliott-io · Accepted Answer · 2020-05-04 22:55:47Z

2

It's not the prettiest, but it's functional. It handles all built-in iOS fonts.

Extension:

extension UIFont {
    func italic() -> UIFont? {
        if let italic = UIFont.init(name: "\(self.fontName)-Italic", size: self.pointSize) {
            return italic
        } else if let italic = UIFont.init(name: "\(self.fontName)Italic", size: self.pointSize) {
            return italic
        }
        if let oblique = UIFont.init(name: "\(self.fontName)-Oblique", size: self.pointSize) {
            return oblique
        } else if let oblique = UIFont.init(name: "\(self.fontName)Oblique", size: self.pointSize) {
            return oblique
        }
        var suffixFontName = self.fontName // for font names that have a 2 letter suffix such as ArialMT
        suffixFontName.removeLast(2)
        let suffix = self.fontName.suffix(2)
        if let suffixFontName = UIFont.init(name: "\(suffixFontName)-Italic\(suffix)", size: self.pointSize) {
            return suffixFontName
        }
        if let suffixFontName = UIFont.init(name: "\(suffixFontName)Italic\(suffix)", size: self.pointSize) {
            return suffixFontName
        }
        // no italic, oblique, or mt italic font found
        return nil
    }
}

Usage:

    let helveticaNeueLightItalic = UIFont(name: "HelveticaNeue-Light", size: 16.0)!.italic()
    print(helveticaNeueLightItalic)

    let helveticaItalic = UIFont(name: "Helvetica", size: 16.0)!.italic()
    print(helveticaItalic)

    let helveticaLightItalic = UIFont(name: "Helvetica-Light", size: 16.0)!.italic()
    print(helveticaLightItalic)

    let arialMtItalic = UIFont(name: "ArialMT", size: 16.0)!.italic()
    print(arialMtItalic)

    let arialMtBoldItalic = UIFont(name: "Arial-BoldMT", size: 16.0)!.italic()
    print(arialMtBoldItalic)

answered May 4, 2020 at 22:55

elliott-io

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3 Comments

Marco Over a year ago

Thanks, I was hoping there's some way to get UIFontDescriptor to do this dirty work. But you're right, this gets the job done and with some unit tests in place it can be future-proofed.

elliott-io Over a year ago

True! Happy to help :-)

Larme Over a year ago

suffixFontName isn't really a suffix, it's rather the name without the suffix, suffix which is the foundry, or can be prefix too (LT, MT, A, BT, FB, URW) and not only 2 letters.

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