anchor.diff:      member x.DepthRange
           with get() = depthRange.Value
           and set r = transact (fun () -> depthRange.Value <- r)
  +
  +    member x.ScaleFactor
  +        with get() = scaleFactor
  +        and set r = scaleFactor <- r
               
       member x.GetVulkanInstanceExtensions() = 
           let b = System.Text.StringBuilder(4096, 4096)
  
positive.code:         )
  
      let desiredSize =
          let mutable width = 0u
          let mutable height = 0u
          system.GetRecommendedRenderTargetSize(&width,&height)
          V2i(int width, int height)
  
  
      let view (t : Trafo3d) =
  
negative.code:         if OpenVR.Chaperone.GetPlayAreaRect(&quad) then
              let quad = 
                  Polygon3d [|
                      V3d(quad.vCorners0.v0, quad.vCorners0.v2, -quad.vCorners0.v1)
                      V3d(quad.vCorners1.v0, quad.vCorners1.v2, -quad.vCorners1.v1)
                      V3d(quad.vCorners2.v0, quad.vCorners2.v2, -quad.vCorners2.v1)
                      V3d(quad.vCorners3.v0, quad.vCorners3.v2, -quad.vCorners3.v1)
                  |]
              Some quad
          else
  