anchor.diff:                         ,(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)
  
positive.code:           '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))
  
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)
  