anchor.diff:  `stream-read-gesture' for the stream encapsulated by
   `stream'. The second return value of this function will be `type'
   if stuff is inserted after the insertion pointer."
  -  (let* ((before (stream-input-buffer stream))
  -         (drei (drei-instance stream))
  +  (let* ((drei (drei-instance stream))
  +         (buffer (buffer drei))
            (*command-processor* drei)
            (was-directly-processing (directly-processing-p drei))
            (minibuffer (or (minibuffer drei) *minibuffer*))
  
positive.code:   (clear-undo-history (buffer (drei-instance stream))))
  
  (defmethod stream-input-buffer ((stream drei-input-editing-mixin))
    ;; NOTE: This is very slow, we should attempt to replace uses of
    ;; this function in McCLIM with something more efficient.
    (with-accessors ((buffer buffer)) (drei-instance stream)
      (let* ((array (buffer-sequence buffer 0 (size buffer))))
        (make-array (length array)
  
negative.code:                     (display-message "Aborted")))))))
        ;; Will also take care of redisplaying minibuffer.
        (display-drei drei)
        (let ((first-mismatch (offset (high-mark buffer))))
          (clear-modify buffer)
          (cond ((null first-mismatch)
                 ;; No change actually took place, even though IP may
                 ;; have moved.
  