anchor.diff:                             (varjo::vertex-count prim)
                              0)))
       (%make-buffer-streamer
  -     :vao nil
  +     :vao 0
        :%start 0
        :%start-byte 0
        :length 0
  
positive.code: 
      (setf (cepl.streams::buffer-stream-start streamer) new-start-pos
            (cepl.streams:buffer-stream-length streamer) c-len)
  
      (cepl.gpu-arrays::with-gpu-array-range-as-pointer
          (g-ptr g-arr new-start-pos c-len
  
negative.code:      :arr cepl.types::+null-buffer-backed-gpu-array+
       :gpu-arrays nil)))
  
  (defun buffer-streamer-push (c-array streamer &optional new-primitive)
    (assert (= (length (c-array-dimensions c-array)) 1))
    (let* ((g-arr (buffer-streamer-arr streamer))
           (g-len (first (gpu-array-dimensions g-arr)))
  