anchor.diff:  
   (defdfun %next-event (window &key blocking)
     "Real next-event implementation."
  +  (declare (ignore window blocking))
     (error 'not-implemented))
   
   ;; method based event handling
  
positive.code: ;; Default implementation
  (defdfun gl-get-proc-address (proc-name)
    "Get foreign pointer to the GL extension designed by PROC-NAME."
    (error 'not-implemented))
  
  (defdfun create-gl-context (window &key make-current major minor)
    "Creates a new OpenGL context of the specified version for the provided window
     and optionally make it current. If major and minor are NIL old style context creation is
     used."
    (error 'not-implemented))
  
  (defdfun destroy-gl-context (ctx)
    "Detach and release the provided OpenGL context."
    (error 'not-implemented))
  
  (defdfun attach-gl-context (window ctx)
    "Makes CTX the current OpenGL context and attach it to WINDOW."
    (error 'not-implemented))
  
  (defdfun detach-gl-context (ctx)
    "Make the provided OpenGL context no longer current."
    (error 'not-implemented))
  
  (defdfun create-window (title width height &key major minor
  
negative.code:    Major and minor arguments specify the context version to use, when NIL
     (default value) old style gl context is created, otherwise framebuffer config
      based context creation is used."
    (declare (ignore title width height major minor double-buffer stereo red-size
                     green-size blue-size alpha-size depth-size accum-buffer accum-red-size
                     accum-green-size accum-blue-size stencil-buffer stencil-size))
    (error 'not-implemented))
  
  (defdfun destroy-window (window)
    "Destroy the provided GL window."
    (declare (ignore window))
    (error 'not-implemented))
  
  (defdfun toggle-fullscreen (window)
    "Switch display resolution to WINDOW dimensions and make WINDOW fullscreen."
    (declare (ignore window))
    (error 'not-implemented))
  
  (defdfun show-window (window)
    "Make WINDOW visible."
    (declare (ignore window))
    (error 'not-implemented))
  
  (defdfun hide-window (window)
    "Make WINDOW not visible."
    (declare (ignore window))
    (error 'not-implemented))
  
  (defdfun set-window-title (window title)
    "Set WINDOW title to TITLE."
    (declare (ignore window title))
    (error 'not-implemented))
  
  (defdfun swap-buffers (window)
    "Swaps GL buffers."
    (declare (ignore window))
    (error 'not-implemented))
  
  ;;; Events handling
  