From: Alan Mackenzie <acm@muc.de>
To: Drew Adams <drew.adams@oracle.com>
Cc: Eli Zaretskii <eliz@gnu.org>, dgutov@yandex.ru, emacs-devel@gnu.org
Subject: Re: A vision for multiple major modes: some design notes
Date: Fri, 22 Apr 2016 08:13:44 +0000 [thread overview]
Message-ID: <20160422081344.GA1873@acm.fritz.box> (raw)
In-Reply-To: <553ab39a-eeaf-4fb7-b8ae-e0592f27db6e@default>
Hello, Drew.
On Thu, Apr 21, 2016 at 03:01:12PM -0700, Drew Adams wrote:
> [More interesting details. Thx.]
> > Given a buffer position, we need to be able to find the corresponding
> > island chain. "Obviously", we do this with a text property, which we
> > might as well call `island', or possibly `chain'. Since successive
> > accesses to chain local variables are very likely to be in the same
> > chain most of the time, we will cache the "current" chain in buffer
> > local variables.
> I guess you are referring to the possibility of more than one
> chain having an island at point, and wanting to pick up the right
> one as the "current" chain - so you check a text property, which
> identifies the chain that is currently active. Is that right?
Er, no. ;-) Even when there is only one island at point, we still need
to determine it. A text property is a good way of doing this.
> > When it comes to movement and search primitives, we want to adapt these
> > so that the impact on existing major modes is minimised. Ideally, we
> > would want major modes to "see" only their own islands (or lack
> > thereof). Thus we treat irrelevant islands as blocks of whitespace. It
> > seems to make sense to have such islands matched by subexpressions in
> > regexps which match spaces. This would obviate the need to amend a
> > great number of regexps currently coded in major modes.
> For search, at least, I don't see why you don't make use of
> `isearch-filter-predicate'. That's what I do in my code, to
> search only within (or without: complement) a set of zones
> (~chain of islands). That seems simple and cheap.
Thanks, I didn't know about that variable. But it may not be widely
applicable enough.
> [I also optionally dim the non-islands during search (or the
> non-non-islands, if complementing), so the areas being searched
> stand out more.]
That's another matter, at a different level of abstraction from the main
topic.
> > On the other hand, when a user does C-s or C-M-s, the Right Thing is
> > surely to search the buffer as a whole, without regard to islands. We
> > therefore need a flag which instructs the primitives how to behave when
> > there are islands. We might as well call this flag `in-islands', for
> > want of a better name.
> `isearch-filter-predicate'. It can let code know whether
> you are island-searching or not.
That would only work for isearch.
> > The user will, from time to time, delete the delimiters which define
> > islands, and will insert other ones.
> FWIW, markers as delimiters do not have that problem.
I think they do. What happens when you have two islands bounded by four
markers, and you delete a region containing the two middle markers;
MaaaaaaaaaaaM MbbbbbbbbbbbbbM
dddddddddddddddddd
? You might well not want the two islands a and b to be coalesced.
--
Alan Mackenzie (Nuremberg, Germany).
next prev parent reply other threads:[~2016-04-22 8:13 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-04-20 19:44 A vision for multiple major modes: some design notes Alan Mackenzie
2016-04-20 21:06 ` Drew Adams
2016-04-20 23:00 ` Drew Adams
2016-04-21 12:43 ` Alan Mackenzie
2016-04-21 14:24 ` Stefan Monnier
2016-04-23 2:20 ` zhanghj
2016-04-23 22:36 ` Dmitry Gutov
2016-04-21 16:05 ` Drew Adams
2016-04-21 16:31 ` Eli Zaretskii
[not found] ` <<64f1d39a-dfd0-44ca-86c1-b4d6104b5702@default>
[not found] ` <<83oa926i0e.fsf@gnu.org>
2016-04-21 16:59 ` Drew Adams
2016-04-21 19:55 ` Eli Zaretskii
[not found] ` <<<64f1d39a-dfd0-44ca-86c1-b4d6104b5702@default>
[not found] ` <<<83oa926i0e.fsf@gnu.org>
[not found] ` <<791d74d1-2b1d-4304-8e7e-d6c31af7aa41@default>
[not found] ` <<83eg9y68jy.fsf@gnu.org>
2016-04-21 20:26 ` Drew Adams
2016-04-20 22:27 ` Phillip Lord
2016-04-21 9:14 ` Alan Mackenzie
2016-04-22 12:45 ` Phillip Lord
2016-04-21 14:17 ` Eli Zaretskii
2016-04-21 21:33 ` Alan Mackenzie
2016-04-21 22:01 ` Drew Adams
2016-04-22 8:13 ` Alan Mackenzie [this message]
2016-04-22 17:04 ` Drew Adams
2016-04-22 9:04 ` Eli Zaretskii
2016-06-13 21:17 ` John Wiegley
2016-06-14 13:13 ` Alan Mackenzie
2016-06-14 16:27 ` John Wiegley
2016-04-21 22:19 ` Alan Mackenzie
2016-04-22 8:48 ` Eli Zaretskii
2016-04-22 22:35 ` Alan Mackenzie
2016-04-23 7:39 ` Eli Zaretskii
2016-04-23 17:02 ` Alan Mackenzie
2016-04-23 18:12 ` Eli Zaretskii
2016-04-23 18:26 ` Dmitry Gutov
2016-04-23 21:08 ` Alan Mackenzie
2016-04-24 6:29 ` Eli Zaretskii
2016-04-24 16:57 ` Alan Mackenzie
2016-04-24 19:59 ` Eli Zaretskii
2016-04-25 6:49 ` Andreas Röhler
2016-04-22 13:42 ` Andy Moreton
2016-04-23 17:14 ` Alan Mackenzie
2016-04-22 14:33 ` Dmitry Gutov
2016-04-22 18:58 ` Richard Stallman
2016-04-22 20:22 ` Alan Mackenzie
2016-04-23 12:27 ` Andreas Röhler
2016-04-23 12:38 ` Richard Stallman
2016-04-23 17:31 ` Alan Mackenzie
2016-04-24 9:22 ` Richard Stallman
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