anchor.diff:    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-id fbo-obj) (or id (first (gl::gen-framebuffers 1))))
     (setf (%fbo-clear-mask fbo-obj)
           (or clear-mask
               (cffi:foreign-bitfield-value
  
positive.code: ;;----------------------------------------------------------------------
  
  (defun %delete-fbo (fbo)
    (gl:delete-framebuffers (listify (%fbo-id fbo))))
  
  
  (defmethod free ((thing fbo))
  
negative.code:              t))))
  
  (defun %get-default-texture-format (attachment)
    (cond ((numberp attachment) :rgba8)
  	((eq attachment :d) :depth-component24)
  	(t (error "No default texture format for attachment: ~s" attachment))))
  
  (defun attachment-compatible (attachment-name image-format)
    (case attachment-name
  