Re: How to add pseudo vector types

[Fu Yuan]

> 在 2021年8月3日，上午7:48，Eli Zaretskii <eliz@gnu.org> 写道：
> 
> 
>> 
>> From: Yuan Fu <casouri@gmail.com>
>> Date: Fri, 30 Jul 2021 10:17:22 -0400
>> Cc: Stephen Leake <stephen_leake@stephe-leake.org>,
>> Clément Pit-Claudel <cpitclaudel@gmail.com>,
>> Stefan Monnier <monnier@iro.umontreal.ca>,
>> emacs-devel@gnu.org
>> 
>>> That said, it looks like the code is correct: you should record the
>>> changes in the entire buffer, but only pass to TS the changes inside
>>> the restriction BEGV..ZV that is in effect at the time of the re-parse
>>> call.  Btw, I don't see the code that filters changes reported to TS
>>> by their positions against the restriction; did I miss something?
>> 
>> Yes, I do clip the change to the visible portion:
>> 
>> ts_record_change (ptrdiff_t start_byte, ptrdiff_t old_end_byte,
>>          ptrdiff_t new_end_byte)
>> {
>>  eassert(start_byte <= old_end_byte);
>>  eassert(start_byte <= new_end_byte);
>> 
>>  Lisp_Object parser_list = Fsymbol_value (Qtree_sitter_parser_list);
>> 
>>  while (!NILP (parser_list))
>>    {
>>      Lisp_Object lisp_parser = Fcar (parser_list);
>>      TSTree *tree = XTS_PARSER (lisp_parser)->tree;
>>      if (tree != NULL)
>>    {
>>      /* We "clip" the change to between visible_beg and
>>         visible_end.  It is okay if visible_end ends up larger
>>         than BUF_Z, tree-sitter only access buffer text during
>>         re-parse, and we will adjust visible_beg/end before
>>         re-parse.  */
>>      ptrdiff_t visible_beg = XTS_PARSER (lisp_parser)->visible_beg;
>>      ptrdiff_t visible_end = XTS_PARSER (lisp_parser)->visible_end;
>> 
>>      ptrdiff_t visible_start =
>>        max (visible_beg, start_byte) - visible_beg;
>>      ptrdiff_t visible_old_end =
>>        min (visible_end, old_end_byte) - visible_beg;
>>      ptrdiff_t visible_new_end =
>>        min (visible_end, new_end_byte) - visible_beg;
>> 
>>      ts_tree_edit_1 (tree, visible_start, visible_old_end,
>>              visible_new_end);
>>      XTS_PARSER (lisp_parser)->need_reparse = true;
>> 
>>      parser_list = Fcdr (parser_list);
> 
> Hmm... so a change that begins before the restriction and ends inside
> the restriction will be sent as if it began at BEGV?  And the rest of
> the change will be discarded?  Shouldn't you split such changes in
> tow, send to TS the part inside the restriction, and store the rest
> for the future, when/if the buffer is widened?

Tree-sitter doesn’t care about the content in a change, it will re-scan the 
buffer content when it re-parses. We only need to inform it the range of the 
change, so it knows where to re-scan when it re-parses. When the buffer is 
widened, we will tell tree-sitter that range [BUF_BEG, BUF_BEGV] has changed, 
and it will re-scan that part when re-parsing. So the part outside the narrowed 
region will be parsed correctly.

Yuan