RevDoc PreviewContext 2

RevDoc PreviewContext 2.swift

struct LargePreviewContextKey: PreviewContextKey {
  static var defaultValue: Custom = .veryLarge
  typealias Value = Custom
}
enum Custom {
  case large, veryLarge, tooBig
  
  var size: CGSize {
    switch self {
    
    case .large:
      return CGSize(width: 400, height: 400)
    case .veryLarge:
      return CGSize(width: 500, height: 500)
    case .tooBig:
      return CGSize(width: 600, height: 600)
    }
  }
}
struct LargePreviewContext: PreviewContext {
  subscript<Key>(key: Key.Type) -> Key.Value where Key : PreviewContextKey {
    return key.defaultValue
  }
  let custom: Custom
  public init(family: Custom) {
    self.custom = family
  }
}

extension View {
  public func previewContext<C>(custom: C) -> some View where C : PreviewContext {
    return Group {
      if let context = custom as? LargePreviewContext {
        self.previewLayout(.fixed(width: context.custom.size.width, height: context.custom.size.height))}
      else {
        self.previewContext(custom)
      }
    }
  }
}

struct ContentView_Previews: PreviewProvider {
  
  static var previews: some View {
    ContentView()
      .previewContext(LargePreviewContext(family: .veryLarge))
    ContentView()
      .previewContext(custom: LargePreviewContext(family: .veryLarge))
  }
}