anchor.diff:                      Log.stop()
                   )
   
  -                handle.ReleaseCurrent()
  -                ctx.CurrentContextHandle <- None
  -                ContextHandle.Current <- None
   
       new(enableDebug) = new OpenGlApplication(true, enableDebug)
       new() = new OpenGlApplication(true, false)
  
positive.code: 
      let init =
          let initialized = ref false
          fun (ctx : Context) (handle : ContextHandle)->
              if not !initialized then
                  initialized := true
                  handle.MakeCurrent()
  
                  ctx.CurrentContextHandle <- Some handle
                  ContextHandle.Current <- Some handle
  
                  using ctx.ResourceLock (fun _ ->
                      try GLVM.vmInit()
  
negative.code:         
          match ctrl with
              | :? RenderControl as ctrl ->
                  if Config.useSharingControl then
                      let impl = new OpenGlSharingRenderControl(runtime, samples)
                      ctrl.Implementation <- impl
                      init ctx
                  else 
                      let impl = new OpenGlRenderControl(runtime, enableDebug, samples) 
                      ctrl.Implementation <- impl
                      init ctx 
              | _ ->
                  failwithf "unknown control type: %A" ctrl
                      
  