anchor.diff:            'fbo-target-not-valid-constant
             :target target)
     (labels (;;--------------------------------------------------------------
  -           (draw-buffer-pattern-p (draw-buffers)
  -             (and (listp draw-buffers)
  -                  (eq (first draw-buffers) 'color-attachments)
  -                  (every #'integerp (rest draw-buffers))))
              (gen-draw-buffers-from-fbo (ctx fbo)
                (alexandria:with-gensyms (ptr len)
                  `(let ((,ptr (%fbo-draw-buffer-map ,fbo))
  
positive.code:                        ,(if with-blending
                               `(cepl.blending::%with-blending ,fbo t nil ,@body)
                               `(progn ,@body))))
                     ((draw-buffer-pattern-p draw-buffers)
                      `(progn
                         ,(gen-draw-buffer-call-from-pattern ctx draw-buffers)
                         ,@body))
                     (t
                      `(progn
                         ,(gen-draw-buffer-call-from-array-form ctx draw-buffers)
  
negative.code:                   (setf (cepl.context::%cepl-context-current-draw-buffers-len ,ctx)
                          ,len)
                    (values))))
             (gen-draw-buffer-call-from-array-form (ctx form)
               (alexandria:with-gensyms (l-arr l-arr-len ptr)
                 `(let* ((,l-arr ,form)
  