How to set kern Persian Numbers in SwiftUI - swiftui

Question

I'm trying to kern Persian numbers but .kerning() doesn't work.
Do you know any another way to set kern in persian numbers?
Text(250000, format: .number)
.kerning(5)
Text("250000")
.kerning(5)
Text(25000.asCurrencyFa)
.kerning(5)
This is my extension how I format the numbers:
extension Int {
var asCurrencyFa: String {
let formatter = NumberFormatter()
formatter.numberStyle = .currency
formatter.locale = Locale(identifier: "fa_IR")
formatter.currencySymbol = ""
return formatter.string(from: self as NSNumber)!
}
}

Answer 1

Kerning (really "expansion" here since this isn't really kerning IMO) is a function of the font, and the default system font (.SFUI-Regular, but I'm pretty sure it's actually SF Arabic) does not appear to support expanding Persian digits. It will expand Persian letters somewhat. For example, فارسی, with .kern(10) displays this way vs "normal."
That said, there are fonts that support expanding Persian digits. For example, Geeza Pro:
let ctFont = CTFontCreateWithName("GeezaPro" as CFString, 16, nil)
...
Text(25000.asCurrencyFa)
.font(Font(ctFont))
Text(25000.asCurrencyFa)
.font(Font(ctFont))
.kerning(10)
One approach to get the "look" is to add HAIR SPACE U+200A between all the characters:
return formatter.string(from: self as NSNumber)!
.map(String.init).joined(separator: "\u{200A}")
This will be a little wider than expected because the HAIR SPACE has width of its own, plus there are two "kernings" per digit pair rather than one. But I do believe it will work with every font. I tried using various zero-width spaces, but they're mostly ignored, except around the comma.