anchor.diff:          with get () = autoInvalidate
           and set v = autoInvalidate <- v
   
  -
  +    /// <summary> Returns true if the control has been fully initialized.</summary> 
  +    member x.IsLoaded 
  +        with get () = loaded
   
       interface IInvalidateControl with
           member x.IsInvalid = needsRedraw
  
positive.code: 
  
      override x.OnHandleCreated(e) =
          let c = OpenTK.Graphics.GraphicsContext.CurrentContext
          GL.Hint(HintTarget.PointSmoothHint, HintMode.Fastest)
          GL.Enable(EnableCap.TextureCubeMapSeamless)
          GL.Disable(EnableCap.PolygonSmooth)
  
  
negative.code:                 x.Invalidate()
          
      override x.OnPaint(e) =
          base.OnPaint(e)
          loaded <- true
          if x.OnPaintRender then
              x.Render()
                      
  