anchor.diff:        (gl:bind-buffer :array-buffer 0)
         (gl:bind-buffer :array-buffer box-buffer)
         (gl:buffer-data :array-buffer :static-draw
  -                      (make-gl-array (vector xmin ymax xmin ymin xmax ymin xmax ymax)))
  +                      (make-gl-array (vector xmin ymax xmin ymin xmax ymax xmax ymin)))
         (gl:bind-buffer :array-buffer 0)
         (make-vstring :content str :xmin xmin :xmax xmax :ymin ymin :ymax ymax
                       :buffer buffer :box-buffer box-buffer :count (/ count 4)))))
  
positive.code: (defvar *glyph-translation* nil)
  (defvar *glyph-scale* nil)
  (defvar *glyph-rotate* nil)
  (defvar *bounding-box-program* nil)
  (defvar *bounding-box-size* nil)
  (defvar *bounding-box-color* nil)
  (defvar *bounding-box-translation* nil)
  (defvar *bounding-box-scale* nil)
  (defvar *bounding-box-rotate* nil)
  
  ; Glyph-table
  ; :font := zpb-ttf:font
  
negative.code:   (gl:stencil-op :keep :invert :invert)
    (gl:color-mask nil nil nil nil)
    (gl:use-program *glyph-program*)
  ;  (gl:enable-vertex-attrib-array 0)
  ;  (gl:enable-vertex-attrib-array 1)
    (gl:bind-buffer :array-buffer (vstring-buffer vs))
    (gl:vertex-attrib-pointer +glyph-vertex-loc+ 2 :float nil 16 0)
    (gl:vertex-attrib-pointer +glyph-attrib-loc+ 2 :float nil 16 8)
    (gl:draw-arrays :triangles 0 (vstring-count vs))
  ;  (gl:disable-vertex-attrib-array 0)
  ;  (gl:disable-vertex-attrib-array 1)
    ;(gl:use-program 0)
    (gl:disable :sample-alpha-to-coverage)
    (gl:stencil-func :notequal 0 1)
    (gl:stencil-op :keep :keep :keep)
    (gl:color-mask t t t t)
    (gl:use-program *bounding-box-program*)
  ;  (gl:enable-vertex-attrib-array 0)
    (gl:bind-buffer :array-buffer (vstring-box-buffer vs))
    (gl:vertex-attrib-pointer +bounding-box-vertex-loc+ 2 :float nil 0 0)
    (gl:draw-arrays :triangle-strip 0 4)
  ;  (gl:disable-vertex-attrib-array 0)
    (gl:use-program 0)
    (gl:disable :stencil-test))
  
  