anchor.diff:    (loop for i in (edition-screen-creation-boxes it) do
          (glaw:render-bbox i))
     (glaw:set-color/rgb 1.0 1.0 1.0 1.0)
  -  (multiple-value-bind (x y z) (glaw:shape-get-vertex (edition-screen-shape it)
  +  (multiple-value-bind (x y z) (glaw:shape-get-vertex/values (edition-screen-shape it)
                                                         (edition-screen-selection it))
       (glaw:format-at 100 160 *font* "Selection: ~A;~A;~A" x y z)))
   
  
positive.code:   (setf (edition-screen-selection-boxes scr) '())
    (loop for i below (glaw:shape-nb-vertices (edition-screen-shape scr)) do
         (let ((box (glaw:create-bbox-from-shape (edition-screen-selection-shape scr))))
           (multiple-value-bind (x y z) (glaw:shape-get-vertex (edition-screen-shape scr) i)
             (declare (ignore z))
             (multiple-value-bind (scr-x scr-y) (glaw:view-to-screen x y (edition-screen-view scr))
               (glaw:bbox-translate box scr-x scr-y)))
  
negative.code: 
  (defun edition-screen-translate-vertex (scr index dx dy)
    (let ((shape (edition-screen-shape scr)))
      (multiple-value-bind (x y z) (glaw:shape-get-vertex/values shape index)
        (glaw:shape-set-vertex shape index (+ x dx) (+ y dy) z)))
    (edition-screen-update-boxes scr))
  
  