A SwiftUI Shape that draws a polygon with a given number of corners and a corner radius.

RoundedPolygon.swift

//
//  RoundedPolygon.swift
//
//  Created by Nate on 2022-10-17.
//

import SwiftUI

struct RoundedPolygon: Shape {
    
    private let radius: CGFloat
    private let points: Int
    
    init(cornerRadius: CGFloat, points: Int) {
        self.radius = cornerRadius
        self.points = points
    }
    
    private func calculateCorners(in rect: CGRect,
                                  withRadius radius: CGFloat,
                                  points: Int) -> [CGPoint] {
        var corners = [CGPoint]()
        
        let step: CGFloat = (.pi * 2) / CGFloat(points)
        
        let radius: CGFloat = min(rect.midX, rect.midY)
        
        for i in 0 ..< points {
            let theta = CGFloat(i) * step
            let x = radius + cos(theta) * radius
            let y = radius + sin(theta) * radius
            corners.append(CGPoint(x: x, y: y))
        }
        return corners
    }
    
    func path(in rect: CGRect) -> Path {
        
        let corners = calculateCorners(in: rect,
                                       withRadius: radius,
                                       points: points)
        
        guard corners.count >= 3 else { return Path() }
      
        var path = Path()
        
        let c1 = corners[0]
        let c2 = corners[corners.count - 1]
        let startPoint = CGPoint(x: (c1.x + c2.x) / 2,
                                 y: (c1.y + c2.y) / 2)
        
        path.move(to: startPoint)
        
        for n in 0..<corners.count {
            let current = corners[n]
            let next = n < (corners.count - 1) ? corners[n + 1] : corners[0]
            path.addArc(tangent1End: current, tangent2End: next, radius: radius)
        }
        
        return path
    }
}