Native source code for CodeSlicing episode exploring overlay / background modifiers vs ZStack - demo-02

OverlayVsZStackDemo02Native.swift

//
//  OverlayVsZStackDemo02Native.swift
//
//  Permission is hereby granted, free of charge, to any person obtaining a copy
//  of this software and associated documentation files (the "Software"), to deal
//  in the Software without restriction, including without limitation the rights
//  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
//  of the Software, and to permit persons to whom the Software is furnished to do so,
//  subject to the following conditions:
//
//  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
//  INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
//  PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
//  COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
//  AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
//  WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
//
//  Copyright © 2021 Adam Fordyce. All rights reserved.
//

import SwiftUI

private func Square(_ color: Color, _ sideLength: CGFloat = 100) -> some View {
    Rectangle()
        .fill(color)
        .frame(width: sideLength, height: sideLength)
}

struct OverlayVsStackDemo02Native: View {
    
    @State private var size = CGSize(width: 0, height: 0)
    
    var body: some View {
        let centerSquare = Square(.yellow)
        let bigSquare = Square(.white.opacity(0.5), 200)
        let littleSquare = Square(.blue, 50)
        VStack {
            createPattern {
                centerSquare
                    .background(bigSquare)
            }
            createPattern {
                ZStack(alignment: .topLeading) {
                    bigSquare
                        .frame(width: size.width, height: size.height)
                    ZStack(alignment: .bottomTrailing) {
                        centerSquare
                            .geometryReaderNative { geo in
                                size = geo.size
                            }
                        littleSquare
                    }
                    littleSquare
                }
                .frame(width: size.width, height: size.height)
            }
        }
    }
    
    private func createPattern<Content: View>(@ViewBuilder content: () -> Content) -> some View {
        let redSquare = Square(.red)
        return VStack {
            redSquare
            HStack {
                redSquare
                content()
                redSquare
            }
            redSquare
        }
    }
}

// added the implementation for geometryReader here. Called it native so it doesn't
// interfere with the PureSwiftUI version if you have that installed

private extension View {
    
    func geometryReaderNative(_ geoCallback: @escaping (GeometryProxy) -> ()) -> some View {
        geometryReaderNative(id: 1, geoCallback)
    }
    
    func geometryReaderNative<T: Hashable>(id: T, _ geoCallback: @escaping (GeometryProxy) -> ()) -> some View {
        overlay(GeometryReader { (geo: GeometryProxy) in
            Color.clear.onAppear {
                geoCallback(geo)
            }
            .id(id)
        })
    }
}

struct OverlayVsStackDemo02Native_Previews: PreviewProvider {
    struct OverlayVsStackDemo02Native_Harness: View {

        var body: some View {
            OverlayVsStackDemo02Native()
                .padding(20)
                .foregroundColor(.white)
                .background(Color(white: 0.1))
        }
    }

    static var previews: some View {
        OverlayVsStackDemo02Native_Harness()
            .previewLayout(.sizeThatFits)
    }
}