SwiftUI Slider Reskin

CustomSlider.swift

import SwiftUI

struct ContentView: View {
    @State var sliderValue: Double = 0.5
    var body: some View {
        CustomSlider(value: $sliderValue)
    }
}

struct CustomSlider<V: BinaryFloatingPoint>: View where V.Stride: BinaryFloatingPoint {
    @Binding var value: V
    
    var body: some View {
        Slider(value: $value)
            .overlay(
                GeometryReader { proxy in
                    ZStack(alignment: .leading) {
                        RoundedRectangle(cornerRadius: proxy.size.height*0.5)
                            .fill(Color.init(white: 0.75))
                            .overlay(
                                RoundedRectangle(cornerRadius: proxy.size.height*0.5)
                                    .stroke(Color.init(white: 0.5), lineWidth: 1)
                                )
                        
                        RoundedRectangle(cornerRadius: proxy.size.height*0.5)
                            .fill(.blue)
                            .frame(width: (proxy.size.width-proxy.size.height) * CGFloat(self.value) + proxy.size.height)
                        
                        Circle()
                            .fill(.white)
                            .padding(1)
                            .offset(x: (proxy.size.width-proxy.size.height) * CGFloat(self.value))
                    }
                }
                .allowsHitTesting(false)
            )
    }
}

#Preview {
    ContentView()
        .padding()
}