anchor.diff:  (defstruct drawing-options
     "A set of options for how to display a stroke."
     (face (make-face))
  -  (function +default-stroke-drawer-dispatcer+))
  +  (function +default-stroke-drawer-dispatcher+))
   
   (defun drawing-options-equal (o1 o2)
     "Return true if `o1' and `o2' are equal, that is, they specify
  
positive.code:     (and (equal (face-ink f1) (face-ink f2))
           (equal (face-style f1) (face-style f2))
           (or (not (eq (drawing-options-function o1)
                        +default-stroke-drawer-dispatcer+))
               (eq (drawing-options-function o2)
                   +default-stroke-drawer-dispatcer+))
           (or (not (eq (drawing-options-function o2)
                        +default-stroke-drawer-dispatcer+))
               (eq (drawing-options-function o1)
                   +default-stroke-drawer-dispatcer+)))))
  
  (defconstant +default-drawing-options+ (make-drawing-options)
    "The default set of drawing options used for strokes when
  
negative.code:   (ink +foreground-ink+)
    (style nil))
  
  (defconstant +default-stroke-drawer-dispatcher+
    #'(lambda (stream view stroke cursor-x cursor-y default-drawing-fn)
        (funcall default-drawing-fn stream view stroke cursor-x cursor-y))
    "A simple function of six arguments that simply calls the first
  