anchor.diff:      (cond ((next current-line)
              (setf (prev (next current-line)) new-line))
             (t (setf (last-line *editor*) new-line)))
  +    (incf (version current-line))
       (setf (next current-line) new-line
             (fill-pointer (data current-line)) (point-offset *editor*))
       (setf (point-line *editor*) new-line
  
positive.code:     (truncate (- (mezzanine.gui.compositor:height (window *editor*)) top bottom)
                (mezzanine.gui.font:line-height (font *editor*)))))
  
  (defun put-string (string pen y start end)
    (multiple-value-bind (left right top bottom)
        (mezzanine.gui.widgets:frame-size (frame *editor*))
      (loop
         with font = (font *editor*)
         with y-pos = (+ (* y (mezzanine.gui.font:line-height font)) (mezzanine.gui.font:ascender font))
         with fb = (mezzanine.gui.compositor:window-buffer (window *editor*))
         with colour = (foreground-colour *editor*)
         for ch-offset from start below end
         for glyph = (mezzanine.gui.font:character-to-glyph font (aref string ch-offset))
         for mask = (mezzanine.gui.font:glyph-mask glyph)
         for advance = (mezzanine.gui.font:glyph-advance glyph)
         do
           (mezzanine.gui:bitset-argb-xrgb-mask-8 (array-dimension mask 0) (array-dimension mask 1)
                                                  colour
                                                  mask 0 0
                                                  fb
                                                  (+ top (- y-pos (mezzanine.gui.font:glyph-yoff glyph)))
                                                  (+ left pen (mezzanine.gui.font:glyph-xoff glyph)))
           (incf pen advance)
         finally (return pen))))
  
  
negative.code:    (%point-column-hint :initarg :point-column-hint :accessor point-column-hint)
     (%foreground-colour :initarg :foreground-colour :accessor foreground-colour)
     (%background-colour :initarg :background-colour :accessor background-colour)
     ;; Redisplay state.
     (%window-top-line :initarg :window-top-line :accessor window-top-line)
     (%window-top :initarg :window-top :accessor window-top)
     (%current-screen :initarg :current-screen :accessor current-screen)
     (%current-point-logical-line :initarg :current-point-screen-line :accessor current-point-logical-line))
    (:default-initargs :pending-event nil
                       :pending-redisplay nil
                       :csr-x 0 :csr-y 0 :csr-char #\Space
  