anchor.diff:  ;;----------------------------------------------------------------------
   
   (defun %delete-fbo (fbo)
  -  (gl:delete-framebuffers (listify (%fbo-id fbo))))
  +  (gl::delete-framebuffers (listify (%fbo-id fbo))))
   
   
   (defmethod free ((thing fbo))
  
positive.code: (defvar %valid-texture-subset '(:dimensions :element-type :mipmap :immutable))
  
  (defun %gen-textures (pattern)
    (assert (or (listp pattern) (keywordp pattern)))
    (cond
      ;; simple keyword pattern to texture
      ((keywordp pattern)
       (cons (texref
              (make-texture
  	     nil :dimensions (viewport-dimensions (current-viewport))
  
negative.code:   fbo-obj)
  
  (defun post-gl-init (fbo-obj &key id draw-buffer-map clear-mask)
    (setf (%fbo-id fbo-obj) (or id (first (gl::gen-framebuffers 1))))
    (setf (%fbo-clear-mask fbo-obj)
          (or clear-mask
              (cffi:foreign-bitfield-value
  