anchor.diff:  
   (defclass xterm-terminal (sys.int::stream-object)
     ((framebuffer :initarg :framebuffer :reader terminal-framebuffer)
  +   ;; Offsets in the framebuffer.
  +   (x-offs :initarg :x :reader x-offset)
  +   (y-offs :initarg :y :reader y-offset)
      (input :initarg :input)
      (queued-bytes :initarg :queued-bytes)
      (interrupt-character :initarg :interrupt-character :accessor interrupt-character)
  
positive.code:   (setf bottom (clamp bottom 0 (terminal-height term)))
    (when (< top bottom)
      (sys.graphics::bitset (* (- bottom top) 16) (* (terminal-width term) 8)
                        #xFF000000 (terminal-framebuffer term)
                        (* top 16) 0)))
  
  (defun erase (term left right)
    (setf left (clamp left 0 (terminal-width term)))
  
negative.code:              (< left right))
      (sys.graphics::bitset 16 (* (- right left) 8)
                            #xFF000000 (terminal-framebuffer term)
                            (+ (* (y-pos term) 16) (y-offset term)) (+ (* left 8) (x-offset term)))))
  
  (defmethod sys.int::stream-write-byte (byte (stream xterm-terminal))
    (ecase (terminal-state stream)
  