Make some italic text in spite of font hasn't itatic family.

You can make custom font to descriptor with matrix. and this is my way for make italic font even if no has italic trait. 

let angle = CGFloat(tanf(11 * Float.pi / 180))
let transform = CGAffineTransform(a: 1, b: 0, c: angle, d: 1, tx: 0, ty: 0)
let descriptor = UIFontDescriptor(name: "font name", matrix: transform)
let font = UIFont(descriptor: descriptor, size: "font size")

It will be useful to known how to using descriptor like this.