anchor.diff:      let keyboard = new Aardvark.Application.WinForms.Keyboard()
       let mouse = new Aardvark.Application.WinForms.Mouse()
       let sizes = Mod.init (V2i(base.ActualWidth, base.ActualHeight))
  +
  +    let actualSize = 
  +        adaptive {
  +            let! s = sizes
  +            match impl with
  +             | Some v -> 
  +                printfn "switched to impl"
  +                return! v.Sizes
  +             | None -> return s
  +        }
  +
       let mutable inner : Option<IMod<DateTime>> = None
       let time = 
           Mod.custom (fun () -> 
  
positive.code:             | Some task -> cr.RenderTask <- task
              | None -> ()
  
          transact(fun () ->
              cr.Time.AddOutput(time)
              inner <- Some cr.Time
          )
  
          ctrl <- Some c
          impl <- Some cr
  
      override x.OnRenderSizeChanged(e) =
          base.OnRenderSizeChanged(e)
  
negative.code:                 | None -> DateTime.Now
             )
  
      member x.SetControl (self : RenderControl) (c : FrameworkElement) (cr : IRenderTarget) =
          match impl with
              | Some i -> failwith "implementation can only be set once per control"
              | None -> ()
  