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Re: address@hidden: Font Lock on-the-fly misfontification in C++]
From: |
Stefan Monnier |
Subject: |
Re: address@hidden: Font Lock on-the-fly misfontification in C++] |
Date: |
Tue, 01 Aug 2006 15:23:54 -0400 |
User-agent: |
Gnus/5.11 (Gnus v5.11) Emacs/22.0.50 (gnu/linux) |
> It seems that the identification of the "safe place" (in a previously
> unfontified region) needs to be done by a function essentially the same
> as font-lock-extend-region-function, since f-l-multiline properties
> haven't yet been applied. In that case, what is the advantage in using
> f-l-multiline at all?
As opposed to using what? Remember f-l-multiline is about
/rehighlighting/. Think of it as *de*highlighting. I.e. find the places
where there used to be a multiline element but not any more.
> It's going to be more code. Might it, for
> example, be faster?
It's expected to be faster than recomputing this extended region in
before-change-function (since it's the only place where you can do it
otherwise: in after-change-function it's too late (unless you saved the
info somewhere) because the buffer text may not contain the pertinent
info).
>> > Maybe you're right here. But care would be needed to ensure that
>> > there is some boundary between adjacent f-l-multiline regions, such
>> > as in this sort of thing:
>> > foo =
>> > 3 ;bar =
>> > /* ^^ */
>> > 4 ;
>> Yes, that's a problem. I don't even think the current code handles it
>> right.
> Again, this problem doesn't happen with the f-l-extend-region-function
> approach.
[ Not sure what you mean by f-l-extend-region-function, BTW. Is it the
current f-l-extend-region-function in Emacs-CVS, or is it some future
thingy that will be called from f-l-refontify-region?
The current f-l-extend-region-function can't help with
/identification/ any more than f-l-multiline. ]
I expect that the difference is not in the approaches but in their
particular implementation at a particular moment in time.
> When you load that file (having stripped the leading "> >>" from each
> line ;-), only the first 8 "defined"s get fontified. (Up to byte 500
> (jit-lock-chunk-size), perhaps?) If you set font-lock-support-mode to
> nil, the whole caboodle is (at least to begin with) fontified right.
I.e. it's a problem of /identification/, so of course f-l-multiline won't
help you.
> The point I was trying to make was that locating the "safe place" can be
> a long-winded slow operation - that in a piece of code like the above
> (which isn't untypical), the strategy of placing f-l-multiline properties
> might cause this expensive analysis to be done several times per buffer
> change.
I don't understand: the costly operation to find the safe place is what you
need for /identification/. Once you've done that, the f-l-multiline
property allows you to store the resulting info (which you computed for
/identification/, not for f-l-multiline) so you won't have to recompute
it later when deciding what to dehighlight.
Stefan
Re: address@hidden: Font Lock on-the-fly misfontification in C++], Aidan Kehoe, 2006/08/02
- Re: address@hidden: Font Lock on-the-fly misfontification in C++], David Kastrup, 2006/08/02
- Re: address@hidden: Font Lock on-the-fly misfontification in C++], Aidan Kehoe, 2006/08/02
- Re: address@hidden: Font Lock on-the-fly misfontification in C++], David Kastrup, 2006/08/02
- Re: address@hidden: Font Lock on-the-fly misfontification in C++], Aidan Kehoe, 2006/08/02
- Re: address@hidden: Font Lock on-the-fly misfontification in C++], David Kastrup, 2006/08/02
- Re: address@hidden: Font Lock on-the-fly misfontification in C++], Aidan Kehoe, 2006/08/02
- Re: address@hidden: Font Lock on-the-fly misfontification in C++], David Kastrup, 2006/08/02