anchor.diff:                             (varjo::vertex-count prim)
                              0)))
       (%make-buffer-streamer
  -     :vao nil
  +     :vao 0
        :%start 0
        :%start-byte 0
        :length 0
  
positive.code:     (cepl.context::if-gl-context
       (%init-streamer
        (cepl.streams::init-buffer-stream-from-id
         %pre% (cepl.vaos:make-vao gpu-arrays nil)
         gpu-arrays nil 0 len t))
       (make-uninitialized-streamer primitive)
       gpu-arrays)))
  
negative.code: 
      (setf (cepl.streams::buffer-stream-start streamer) new-start-pos
            (cepl.streams:buffer-stream-length streamer) c-len)
  
      (when new-primitive
        (setf (cepl.streams:buffer-stream-primitive streamer) new-primitive))
  
      (cepl.gpu-arrays::with-gpu-array-range-as-pointer
          (g-ptr g-arr new-start-pos c-len
  