anchor.diff:    (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)
  +                          (logior #xFF000000 (background-colour term)) (terminal-framebuffer term)
                             (+ (* top 16) (y-offset term)) (x-offset term))))
   
   (defun erase (term left right)
  
positive.code:                 (t (report-unknown-escape terminal))))
               (#\d
                (setf (y-pos terminal) (1- (or (first (slot-value terminal 'parameters)) 1))))
               (#\m) ; character attributes **
               (#\r) ; set scroll region. **
               (#\h) ; set mode **
               (#\l) ; clear mode **
  
negative.code:   (let ((x (x-pos term)) (y (y-pos term)))
      (when (and (<= 0 x (1- (terminal-width term)))
                 (<= 0 y (1- (terminal-height term))))
        (sys.graphics::bitset 16 8
                              (logior #xFF000000 (background-colour term)) (terminal-framebuffer term)
                              (+ (* y 16) (y-offset term)) (+ (* x 8) (x-offset term)))
        (unless (eql char #\Space)
          (let* ((glyph (sys.int::map-unifont-2d char)))
            (when glyph
              (sys.graphics::bitset-argb-xrgb-mask-1 16 8 (logior #xFF000000 (foreground-colour term))
                                                     glyph 0 0
                                                     (terminal-framebuffer term)
                                                     (+ (* y 16) (y-offset term))
                                                     (+ (* x 8) (x-offset term)))
              (when (bold term)
                (sys.graphics::bitset-argb-xrgb-mask-1 16 7 (logior #xFF000000 (foreground-colour term))
                                                     glyph 0 0
                                                     (terminal-framebuffer term)
                                                     (+ (* y 16) (y-offset term))
                                                     (+ (* x 8) (x-offset term) 1)))))))
      (incf (x-pos term))))
  
  (defun clamp (value min max)
  