anchor.diff:                              let line = textView.TextSnapshot.GetLineFromLineNumber(lineNo)
                               textView.Caret.MoveTo(VirtualSnapshotPoint(textView.TextSnapshot, pos)) |> ignore
                               textView.ViewScroller.EnsureSpanVisible(SnapshotSpan(line.Start, 0), EnsureSpanVisibleOptions.ShowStart))
  -                        children.Add(marker) |> ignore)
  +                        children.Add(marker) |> ignore
  +            } |> Async.StartInThreadPoolSafe
   
       let docEventListener = new DocumentEventListener ([ViewChange.viewportHeightEvent textView; ViewChange.classificationEvent classifier], 
                                      200us, updateDisplay)
  
positive.code:     let mutable markerData = Unchecked.defaultof<_>
      let markerBrush = SolidColorBrush(Color.FromRgb(255uy, 165uy, 0uy))
  
      let updateDisplay () =
          protect (fun _ ->
              if not textView.IsClosed then
                  let span = SnapshotSpan(textView.TextBuffer.CurrentSnapshot, 0, textView.TextBuffer.CurrentSnapshot.Length)
                  let data =
                      classifier.GetClassificationSpans(span)
                      |> Seq.choose (fun classification -> 
  
negative.code:                         else None)
                      |> Seq.distinctBy fst
                      |> Seq.toArray
              
                  if markerData <> data then
                      do! Async.SwitchToContext ctx
                      markerData <- data
                      children.Clear()
                      let totalLines = textView.TextSnapshot.LineCount
  