anchor.diff:              | Some i -> failwith "implementation can only be set once per control"
               | None -> ()
   
  -        self.Content <- c
  +        self.Child <- c
           runtime <- cr.Runtime
   
           match c with
  
positive.code:     override x.OnRenderSizeChanged(e) =
          base.OnRenderSizeChanged(e)
          transact (fun () -> Mod.change sizes (V2i(x.ActualWidth, x.ActualHeight)))
  
      member x.Implementation
          with get() = match ctrl with | Some c -> c | _ -> null
  
negative.code: open System.Windows.Forms.Integration
  
  type RenderControl() =
      inherit Border()
  
      let mutable runtime : IRuntime = Unchecked.defaultof<IRuntime>
      let mutable renderTask : Option<IRenderTask> = None
  