[NTG-context] Can not register the callback functions in MkIV

Hi, Now it seems that we have not allowed to register the callback functions since beta 2010.02.18. For example: \startluacode local old_pre_linebreak_filter = callback.find ('pre_linebreak_filter') local function my_pre_linebreak_filter (head, groupcode) if old_pre_linebreak_filter then old_pre_linebreak_filter (head, groupcode) end print ('This is my pre_linebreak_callback') return true end callback.register ('pre_linebreak_filter', my_pre_linebreak_filter) \stopluacode \starttext This is just a test! \stoptext The 'my_pre_linebreak_filter' function can not work again. Is this a bug? -- Best regards, Li Yanrui