anchor.diff:  
   ;;------------------------------------------------------------
   
  -(defn %set-current-viewport ((cepl-context cepl-context)
  -                             (viewport viewport))
  +(defn-inline %set-current-viewport ((cepl-context cepl-context)
  +                                    (viewport viewport))
       viewport
     (declare (optimize (speed 3) (debug 1) (safety 1))
              (inline viewport-eql)
  
positive.code:     `(with-cepl-context (,ctx)
         (let* ((,old-viewport (current-viewport))
                (,vp ,viewport))
           (%gl:viewport (%viewport-origin-x vp) (%viewport-origin-y vp)
                         (%viewport-resolution-x vp) (%viewport-resolution-y vp))
           (unwind-protect (progn ,@body)
             (%set-current-viewport ,ctx ,old-viewport))))))
  
  
negative.code:     (if (viewport-eql current-viewport viewport)
          viewport
          (progn
            (%gl:viewport
             (%viewport-origin-x viewport) (%viewport-origin-y viewport)
             (%viewport-resolution-x viewport) (%viewport-resolution-y viewport))
            (setf current-viewport viewport)))))
  
  (defun2 current-viewport ()
  