ContentView.swift

import SwiftUI

struct RegularEventCell: View {
    
    let color: Color
    let title: String
    let description: String?
    
    var body: some View {
        
        HStack {
            
            color.frame(width: 3)
            
            VStack (alignment: .leading, spacing: 0) {
                
                Text(title)
                    .font(.caption)
                
                if let desc = description
                {
                    Text(desc)
                        .font(.caption2)
                        .foregroundColor(.secondary)
                }
            }
            
            Spacer()
        }
        .padding([.leading, .trailing], 10)
        .padding([.bottom, .top], 5)
        .readFrame()
    }
}

extension View {
  func readFrame() -> some View {
    background(
      GeometryReader { geometryProxy in
        Color.clear.preference(key: FramePreferenceKey.self, value: [geometryProxy.frame(in: .global)])
      }
    )
  }
}

private struct FramePreferenceKey: PreferenceKey {
  static var defaultValue: [CGRect] = []
  static func reduce(value: inout [CGRect], nextValue: () -> [CGRect])
  {
    value.append(contentsOf: nextValue())
  }
}


struct ModelRow: Identifiable {
    let id: String = NSUUID().uuidString
    let title: String
    let description: String?
}

let rows = [ModelRow(title: "One", description: "First"),
            ModelRow(title: "Two", description: nil),
            ModelRow(title: "Three", description: "Third"),
            ModelRow(title: "Four", description: nil),
            ModelRow(title: "Five", description: "Fifth"),
            ModelRow(title: "Six", description: nil)]

struct ContentView : View {

    @State var rowFrames: [CGRect] = []
    
    var body: some View {
        
        GeometryReader { geometry in // causes VStack to be same size as widget
            
            VStack(alignment: .leading, spacing: 1) {
                
                ForEach(0 ..< rows.count) { rowIndex in
                    
                    Group {
                        RegularEventCell(color: .red, title: rows[rowIndex].title, description: rows[rowIndex].description)
                        Divider()
                    }
                    .opacity(rowIndex < rowFrames.count && rowFrames[rowIndex].maxY < geometry.size.height ? 1 : 0)
                }
                
                Spacer()
            }
        }
        .onPreferenceChange(FramePreferenceKey.self, perform: { value in
            rowFrames = value
            dump(value)
        })
    }
}


struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView().previewLayout(.fixed(width: 200, height: 170))
    }
}