From: Stefan Monnier <monnier@iro.umontreal.ca>
Cc: Richard Stallman <rms@gnu.org>, emacs-devel@gnu.org
Subject: Re: Last steps for pretesting (font-lock-extend-region-function)
Date: Tue, 25 Apr 2006 08:33:29 -0400 [thread overview]
Message-ID: <87fyk1df9o.fsf-monnier+emacs@gnu.org> (raw)
In-Reply-To: <Pine.LNX.3.96.1060425075047.675C-100000@acm.acm> (Alan Mackenzie's message of "Tue, 25 Apr 2006 11:33:55 +0000 (GMT)")
> I find the elisp manual page which describes font-lock-keywords
> ("Search-based Fontification") all but inpenetrable. It's reduced me to
> tears on several occasions. I've just spent five minutes looking through
> it, trying to find the description of the form you suggested to me:
> (".*\\\\\n.*"
> (0 (progn (put-text-property (match-beginning 0) (match-end 0)
> 'font-lock-multiline t)
> nil)))
> . I didn't find it.
Then the problem isn't font-lock-multiline. Please don't mix up matters.
This form is the standard form (except you haven't noticed yet that the
FACENAME part of the font-lock-keywords is not a face symbol but an Elisp
expression whose value after exavluation should be a face). It's:
(MATCHER HIGHLIGHT ...)
where MATCHER is ".*\\\\\n.*" and HIGHLIGHT is of the form MATCH-HIGHLIGHT
which is of the form (SUBEXP FACENAME [OVERRIDE [LAXMATCH]]) where SUBEXP is
0 and FACENAME is (progn ...).
> With respect, Stefan, that's rubbish. You need to know where and how to
> write the above Lisp form (the one starting (".*\\\\n.*" ...)) into
> f-l-keywords. For me, that's perhaps half an hour to an hour of
> frustration trying to find the right place in "Search-based
> Fontification".
If you don't know how font-lock-keywords work, then learn that first before
trying to work on the font-lock support for cc-mode. That'll save you a lot
more time.
> What about the run-time overhead of having an extra text property over
> the entire buffer?
It's not over the entire buffer. And I haven't seen any evidence that it's
noticeable (especially compared the number of `face' properties or of the
`fontified' property added to the whole buffer).
> The f-l-e-r-f, as you envisage it (being called only from
> f-l-default-fontify-r) will also be called at virtually every buffer
> change, since almost every change causes a redisplay.
AFAIK, the case where a single change takes place between redisplay is the
case where there is no performance issue: it takes place at the user's
pace anyway. The important case is when Emacs has more work to do in
response to a user's action, i.e. there's more work to be done until the
next redisplay.
>> Just take a deep breath, a couple of steps back, and try to look at the
>> example use of font-lock-multiline above as if it were very simple.
> I've tried, but I just don't have the intellectual capability to cope
> with such complexity without the greatest of difficulty.
The whole point is that you shouldn't have to. It's like recursion (tho not
nearly as elegant, I must admit): have faith, don't try to simulate it all
in your head, and then it becomes simple.
> You obviously do. Complicated nested structures make my eyes glaze over.
> There's a good chance I'm not the only Emacs hacker who has this sort
> of trouble.
Any Emacs hacker that needs to write complex syntax highlighting rules will
have to learn it anyway unless he prefers to circumvent font-lock and roll
his own instead. Sounds like NIH to me.
> There's an assymetry between our positions: by threatening to remove the
> f-l-e-r-f hook (after-change version), you're trying to force me to use
> the f-l-m mechanism.
Yes.
> You're trying to impose your taste and judgement on me, and I resent this
> quite a lot.
I'm as close as it gets to a font-lock maintainer. So from where I stand,
you're trying to impose your taste and judgment on me.
> I think the f-l-m text property is a revolting kludge, but
> I'm not trying to do away with it. I'm happy enough for other hackers to
> use it, though I'd rather not have to maintain their code afterwards.
> Is there any chance we could bring this discussion to an end, now? The
> things we've been talking about are important, but this discussion has
> taken up an enormous amount of my time, and probably yours too. We've
> both got other urgent things to do.
3 ways this can end:
- Richard says that you're right.
- You convince me that the a-c-f code is better for some realistic case
(e.g. yours).
- I remove the hook in a-c-f.
> My fix is simpler: to recognise that f-l-default-fontify-region performs
> two disparate tasks: (i) Extending the region to be fontified; (ii)
> Fontifying this region. By extracting (ii) into a separate function,
> that function could be called directly from jit-lock-fontify-now,
> bypassing the redundant second massaging of the region.
It has to be in font-lock-default-fontify-buffer since ther'es no guarantee
this is only called from jit-lock-fontify-now. So you're suggesting to add
a redundant call to the extend-region hook. Maybe it's simpler but it's
ugly (because of the redundance, and because it adds a dependency between
jit-lock and font-lock).
> (i) It uses the same hook, font-lock-extend-region-function, as
> f-l-after-change-functions, setting the third parameter, OLD-LEN, to nil;
> (ii) It uses a distinct hook with a new name, say,
> font-lock-extend-chunk-function;
> (iii) It usurps the name f-l-e-r-f from its current use, abolishing the
> region extension mechanism in the f-l-after-change-f/j-l-after-change.
(iv) it reuses the name font-lock-extend-region-function and renames the
a-c-f hook to font-lock-after-change-extend-region-function.
This will happen hopefully today. At the same time
font-lock-after-change-extend-region-function will be moved from font-core
to font-lock (where it belongs) and its make-variable-buffer-local call will
be removed as well (use make-local-variable manually if you need it).
Stefan
next prev parent reply other threads:[~2006-04-25 12:33 UTC|newest]
Thread overview: 80+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-04-17 0:56 Last steps for pretesting Richard Stallman
2006-04-17 8:01 ` Ramprasad B
2006-04-17 8:37 ` Eli Zaretskii
2006-04-18 1:42 ` Richard Stallman
2006-04-19 3:54 ` Ramprasad B
2006-04-19 15:40 ` Richard Stallman
2006-04-20 5:23 ` Ramprasad B
2006-04-18 17:31 ` Bill Wohler
2006-04-19 17:02 ` Alan Mackenzie
2006-04-19 21:23 ` Stefan Monnier
2006-04-19 21:30 ` David Kastrup
2006-04-20 21:35 ` Stefan Monnier
2006-04-20 21:37 ` David Kastrup
2006-04-20 21:44 ` Stefan Monnier
2006-04-20 21:46 ` David Kastrup
2006-04-20 22:50 ` Alan Mackenzie
2006-04-19 22:43 ` Last steps for pretesting (font-lock-extend-region-function) Alan Mackenzie
2006-04-20 9:13 ` Alan Mackenzie
2006-04-20 17:46 ` Stefan Monnier
2006-04-20 18:12 ` Alan Mackenzie
2006-04-20 20:58 ` Stefan Monnier
2006-04-20 22:40 ` Alan Mackenzie
2006-04-20 23:34 ` Stefan Monnier
2006-04-21 7:58 ` Alan Mackenzie
2006-04-21 12:18 ` Stefan Monnier
2006-04-21 19:51 ` Alan Mackenzie
2006-04-21 22:28 ` Stefan Monnier
2006-04-24 19:28 ` Alan Mackenzie
2006-04-24 21:06 ` Stefan Monnier
2006-04-25 6:21 ` Ralf Angeli
2006-04-25 10:53 ` Alan Mackenzie
2006-04-25 18:37 ` Ralf Angeli
2006-04-25 22:00 ` Alan Mackenzie
2006-04-26 6:14 ` Ralf Angeli
2006-04-25 19:26 ` Stefan Monnier
2006-04-25 20:10 ` font-lock-multiline for cc-awk Stefan Monnier
2006-04-26 7:37 ` Alan Mackenzie
2006-04-26 13:55 ` Stefan Monnier
2006-04-25 19:23 ` Last steps for pretesting (font-lock-extend-region-function) Stefan Monnier
2006-04-25 20:18 ` Stefan Monnier
2006-04-25 11:33 ` Alan Mackenzie
2006-04-25 11:59 ` David Kastrup
2006-04-25 12:33 ` Stefan Monnier [this message]
2006-04-25 14:07 ` Alan Mackenzie
2006-04-25 16:05 ` Stefan Monnier
2006-04-25 16:09 ` Stefan Monnier
2006-04-25 21:52 ` Alan Mackenzie
2006-04-25 21:49 ` Alan Mackenzie
2006-04-26 4:50 ` Stefan Monnier
2006-04-24 21:20 ` Stefan Monnier
2006-04-25 7:45 ` Alan Mackenzie
2006-04-25 12:12 ` Stefan Monnier
2006-04-25 21:15 ` Alan Mackenzie
2006-04-26 4:33 ` Stefan Monnier
2006-04-26 8:30 ` Alan Mackenzie
2006-04-26 13:36 ` Stefan Monnier
2006-04-24 21:33 ` Stefan Monnier
2006-04-25 7:27 ` Alan Mackenzie
2006-04-25 12:03 ` Stefan Monnier
2006-04-25 13:14 ` Alan Mackenzie
2006-04-26 0:22 ` Miles Bader
2006-04-25 4:39 ` Tomas Zerolo
2006-04-25 19:02 ` Ralf Angeli
2006-04-25 19:30 ` Stefan Monnier
2006-04-25 20:12 ` Ralf Angeli
2006-04-25 20:26 ` Stefan Monnier
2006-04-25 20:58 ` Ralf Angeli
2006-04-25 21:11 ` Stefan Monnier
2006-04-25 22:30 ` Alan Mackenzie
2006-04-26 4:25 ` Stefan Monnier
2006-04-26 7:44 ` Alan Mackenzie
2006-04-25 22:16 ` Alan Mackenzie
2006-04-26 4:36 ` Stefan Monnier
2006-04-21 23:14 ` Drew Adams
2006-04-19 22:53 ` Last steps for pretesting (true file names in load-history?) Alan Mackenzie
2006-04-20 1:14 ` Last steps for pretesting Richard Stallman
2006-04-24 17:52 ` Richard Stallman
2006-04-20 10:54 ` Reiner Steib
2006-04-21 0:10 ` Richard Stallman
2006-04-21 5:46 ` David Kastrup
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