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bug#57009: Obscure doc string of new variable syntax-wholeline-max
From: |
Alan Mackenzie |
Subject: |
bug#57009: Obscure doc string of new variable syntax-wholeline-max |
Date: |
Sat, 6 Aug 2022 14:32:11 +0000 |
Hello, Lars.
On Sat, Aug 06, 2022 at 14:56:24 +0200, Lars Ingebrigtsen wrote:
> Alan Mackenzie <acm@muc.de> writes:
> > Maximum line length for syntax operations.
> > If lines are longer than that, syntax operations will treat them as
> > chunks
> > of this size. Misfontification may then occur.
> > This is a tradeoff between correctly applying the syntax rules,
> > and avoiding major slowdown on pathologically long lines.
> > Probably introduced at or before Emacs version 29.1.
> > .. There are several bugs here:
> > (i) It is not clear what is meant by "syntax operations". These should
> > be listed and if necessary, explained.
> You mean mention syntax-ppss?
Yes, if that is one of the operations involved. Also, if pertinent,
parse-partial-sexp, forward-list and friends, syntax-propertize, ....
> > (ii) It is not clear what it means for a "syntax operation" to treat a
> > line "as a chunk". This should be explained.
> It's saying that it's processing the line chunk-wise. I think that's
> pretty clear?
If it's clear to you, please explain in a way that's clear to me. :-)
Say the chunk is 64 characters long. Doesn't parse-partial-sexp process
that "as a chunk" anyway? How does one determine where a "chunk" starts
and where it ends? What does "treating a line as a chunk" do that is new
that we didn't do before?
> > (iii) "Misfontification" may well occur, but what about other bad effects
> > of ignoring correct syntax? Don't they deserve a mention?
> Do they?
They might, it depends how clear the rest of an amended text makes
things. For example, will C-M-n still work?
> > (iv) There is no mention of a mechanism to disable this "chunking"
> > effect, whatever it might be. If there is one, it should be
> > documented, if there's not, this should be stated.
> That seems self-evident -- you increase the size?
It is anything but self-evident. It might be by setting the variable to
0, it might be by setting it to nil, it might be, as you suggest by
setting it to a larger size than you think will occur in practice (i.e.
there's no way to disable it). All these ways are in use in Emacs.
> There doesn't really seem to be much to alter here to me, but perhaps
> others have other opinions; adding Stefan to the CCs.
As matters stand, I'd have to read the source code to work out what this
variable is for. I don't think I should have to.
--
Alan Mackenzie (Nuremberg, Germany).