Trying to emulate Picker behaviour inside a List

NavPicker.swift

//
//  NavPicker.swift
//  ColorCore Demo
//
//  Created by Oliver Drobnik on 09.02.21.
//

import SwiftUI

public struct NavPicker<Label, Items> : View where Label : View, Items: CustomStringConvertible & Identifiable
{
	let selection: Binding<Int?>
	let items:[Items]
	let label: Label
	let firstIndexToShow: Int
	
	public init(selection: Binding<Int?>, label: Label, items: [Items], firstIndexToShow: Int = 0)
	{
		self.selection = selection
		self.label = label
		self.items = items
		self.firstIndexToShow = firstIndexToShow
	}
	
	public var body: some View
	{
		NavigationLink(
			destination: NavPickerDetail(selection: selection, items: items, firstIndexToShow: firstIndexToShow)
				.toolbar { ToolbarItem(placement: .principal) { label } }) {
			HStack {
				label
				Spacer()
				if let index = selection.wrappedValue
				{
					Text(items[index].description)
				}
			}
		}
	}
}

public struct NavPickerDetail<Items> : View where Items: CustomStringConvertible & Identifiable
{
	@Binding var selection: Int?
	var items:[Items]
	@State var firstIndexToShow: Int = 0
	
	@State var highlightedIndex: Int?
	
	@Environment(\.presentationMode) var presentationMode
	
	public var body: some View
	{
		List {
			ForEach(firstIndexToShow..<items.count) { index in
				
				HStack {
					Text(items[index].description)
					Spacer()
				}
				.contentShape(Rectangle())
				.onTapGesture {
					self.selection = index
					DispatchQueue.main.asyncAfter(deadline: .now() + 0.1) {
						self.presentationMode.wrappedValue.dismiss()
					}
				}
				.onLongPressGesture(minimumDuration: .greatestFiniteMagnitude, maximumDistance: .greatestFiniteMagnitude, pressing: { self.highlightedIndex = $0 ? index : nil }) {}
				.modifier(CheckmarkModifier(checked: index == selection))
				.background(Color(UIColor.opaqueSeparator)
								.opacity(highlightedIndex == index ? 1.0 : 0.0)
								.padding(EdgeInsets(top: -12, leading: -16, bottom: -12, trailing: -16))
				)
			}
		}
		.listStyle(GroupedListStyle())
	}
}


struct CheckmarkModifier: ViewModifier {
	var checked: Bool = false
	func body(content: Content) -> some View {
		Group {
			if checked {
				ZStack(alignment: .trailing) {
					content
					Image(systemName: "checkmark")
						.resizable()
						.frame(width: 16, height: 16)
						.shadow(radius: 1)
						.foregroundColor(Color.accentColor)
				}
			} else {
				content
			}
		}
	}
}