How to get ScrollView offset in SwiftUI

SwiftUI-ScrollView-offset.swift

struct ContentView: View {
    var body: some View {
        ScrollViewOffset(onOffsetChange: { (offset) in
            print("New ScrollView offset: \(offset)")
        }) {
            VStack {
              ForEach(0..<100) { index in
                Text("\(index)")
              }
            }
        }
    }
}

struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView()
    }
}

struct ScrollViewOffset<Content: View>: View {
  let onOffsetChange: (CGFloat) -> Void
  let content: () -> Content

  init(
    onOffsetChange: @escaping (CGFloat) -> Void,
    @ViewBuilder content: @escaping () -> Content
  ) {
    self.onOffsetChange = onOffsetChange
    self.content = content
  }

  var body: some View {
    ScrollView {
      offsetReader
      content()
        .padding(.top, -8)
    }
    .coordinateSpace(name: "frameLayer")
    .onPreferenceChange(OffsetPreferenceKey.self, perform: onOffsetChange)
  }

  var offsetReader: some View {
    GeometryReader { proxy in
      Color.clear
        .preference(
          key: OffsetPreferenceKey.self,
          value: proxy.frame(in: .named("frameLayer")).minY
        )
    }
    .frame(height: 0)
  }
}

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