SwiftUI view that writes text inside a circle. This is very specific to a project I am working on and not really customizable. It can be extended if you want to.

CircleText.swift

//
//  CircleText.swift
//
//  Created by Cornelius Schiffer on 07.05.22.

import SwiftUI

extension String {
   func size(usingFont font: UIFont) -> CGSize {
        let attributes = [NSAttributedString.Key.font: font]
        let size = self.size(withAttributes: attributes)
        return size
    }
}

extension Font {
  init(_ uiFont: UIFont) {
    self = Font(uiFont as CTFont)
  }
}

struct CircleText: View {
    private struct Letter {
        let character: String
        var offset: Double
    }
    
    private let radius: Double
    
    private let font: Font
    private let textSize: CGSize
    private let text: [Letter]
    
    init(text: String, radius: Double, font: UIFont) {
        self.radius = radius
        
        self.textSize = text.size(usingFont: font)
        self.font = Font(font)

        let circumference = 2 * radius * CGFloat.pi
        let arcLength = circumference / 360
        let totalCharacters = text.count
        
        var letters: [Letter] = []
        var position: Double = 0
        
        // Using the average width for each character plus some bonus
        // This is not ideal, because not every character is the same width. Good enough for now.
        let averageWidthPerCharacter = (self.textSize.width / Double(totalCharacters)).rounded(.up) * 1.3
        let charWidthDegrees = averageWidthPerCharacter / arcLength
        let maxNumberOfCharacters = Int(circumference / averageWidthPerCharacter / 2)
        
        // Rotate left by half the string length to top-center align the text
        let centeringOffset = -(averageWidthPerCharacter * Double(min(maxNumberOfCharacters - 2, totalCharacters) - 1)  / arcLength) / 2
        
        // Store characters and position in degrees on the circle
        for (index, character) in text.enumerated() {
            // Cut off string if it is longer than the maximum number of characters
            if totalCharacters > maxNumberOfCharacters && index > maxNumberOfCharacters - 4  {
                letters.append(Letter(character: "…", offset: position + centeringOffset))
                break
            }

            // Append character and its position
            let charText = String(character)
            letters.append(Letter(character: charText, offset: position + centeringOffset))
            position += charWidthDegrees
        }
        
        self.text = letters
    }
    
    var body: some View {
        ZStack {
            ForEach(Array(text.enumerated()), id: \.offset) { _, letter in
                Text(letter.character)
                    .offset(y: -radius + textSize.height / 2)
                    .rotationEffect(Angle(degrees: letter.offset))
            }
        }
        .font(font)
    }
}

Example usage:

CircleText(
  text: "Your text here", 
  radius: 50, 
  font: UIFont.systemFont(ofSize: 10)
)
.foregroundColor(.white.opacity(0.8))
.background {
  Circle()
  .fill(.black)
  .frame(width: 100, height: 100)
}