anchor.diff:                      
                       // loop until swapped or terminated
                       let mutable swapped = false
  -                    while not swapped && not (this :> RenderProcess2d).Terminated do
  +                    while not swapped && not this.Terminated do
                           swapped <- lock swapLock (fun () ->
                               if swap then
                                   renderer.Swap ()
  
positive.code:                 lock startedLock (fun () -> started <- true)
  
                  // loop until terminated
                  while not (this :> RenderProcess2d).Terminated do
  
                      // loop until rendered or terminated
                      let mutable rendered = false
                      while not rendered && not (this :> RenderProcess2d).Terminated do
                          rendered <-
                              lock submissionLock (fun () ->
                                  match submissionOpt with
  
negative.code:     let swapLock = obj ()
      let mutable swap = false
  
      member this.Terminated =
          (this :> RenderProcess2d).Terminated
  
      interface RenderProcess2d with
  
          member this.Started =
  