CGSize PreferenceKey

// Sample Use
 struct ContentView: View {
        @State private var size: CGSize = .zero
        var body: some View {
            VStack {
                Text("\(size.width)")
                Text("Hello World")
                    .getCGSize($size)
            }
            .padding()
        }
    }

// PreferenceKey

struct CGSizeKey: PreferenceKey {
    static var defaultValue = CGSize.zero
    static func reduce(value: inout CGSize, nextValue: () -> CGSize) {
        value = nextValue()
    }
}

extension View {
    func getCGSize(_ viewSize: Binding<CGSize>) -> some View {
        background(
            GeometryReader { proxy in
                Color.clear
                    .preference(key: CGSizeKey.self, value: proxy.size)
            }
            .onPreferenceChange(CGSizeKey.self) { value in
                viewSize.wrappedValue = value
            }
        )
    }
}