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