anchor.diff:  (defun2 viewport-resolution-y (viewport)
     (%viewport-resolution-y viewport))
   
  -;;- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
  +;;------------------------------------------------------------
   
   (defun2 viewport-origin (viewport)
     (v! (%viewport-origin-x viewport)
  
positive.code:     (%set-resolution viewport (first dim) (second dim))
      value))
  
  ;;- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
  
  (defn-inline viewport-eql ((v0 viewport) (v1 viewport)) boolean
    (and (= (%viewport-resolution-x v0) (%viewport-resolution-x v1))
         (= (%viewport-resolution-y v0) (%viewport-resolution-y v1))
         (= (%viewport-origin-x v0) (%viewport-origin-x v1))
         (= (%viewport-origin-y v0) (%viewport-origin-y v1))))
  
  ;;- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
  
  (defmethod resolution ((viewport viewport))
    (viewport-resolution viewport))
  
negative.code:                    "but we do have a gl context. This is a bug"
                     "because the GL context is not yet available")))))
  
  ;;------------------------------------------------------------
  
  (defmethod dimensions ((viewport viewport))
    (viewport-dimensions viewport))
  