SwiftUI PreferenceKey for Layout Measurement

import SwiftUI

private struct WidthKey: PreferenceKey {
    static var defaultValue: CGFloat = 0
    static func reduce(value: inout CGFloat, nextValue: () -> CGFloat) {
        value = max(value, nextValue())
    }
}

struct MeasuredTitle: View {
    @State private var width: CGFloat = 0

    var body: some View {
        Text("Overview")
            .background {
                GeometryReader { proxy in
                    Color.clear.preference(key: WidthKey.self, value: proxy.size.width)
                }
            }
            .onPreferenceChange(WidthKey.self) { width = $0 }
    }
}