From: Kenichi Handa <handa@m17n.org>
To: Eli Zaretskii <eliz@gnu.org>
Cc: list-general@mohsen.1.banan.byname.net, emacs-devel@gnu.org
Subject: Re: bidi and shaping problems in describe-input-method
Date: Sat, 10 Mar 2012 11:55:54 +0900 [thread overview]
Message-ID: <87r4x1uptx.fsf@m17n.org> (raw)
In-Reply-To: <83pqclzrb5.fsf@gnu.org> (message from Eli Zaretskii on Fri, 09 Mar 2012 18:12:46 +0200)
In article <83pqclzrb5.fsf@gnu.org>, Eli Zaretskii <eliz@gnu.org> writes:
> > In general, it's smarter to use LRM only where necessary.
> Testing whether they are necessary is a problem in itself. You can
> easily avoid inserting the marks for strong L2R characters, but they
> are the minority. Most of the characters are not in that category.
> And of course keyboard layouts include such characters.
> > > > (defun quail-help-require-LRM (char)
> > > > (or (eq (get-char-code-property char 'bidi-class) 'L)
> > > > ...))
> >
> > > It's possible, but why bother? And with this function you will insert
> > > the LRM for many characters that don't need that, like punctuation,
> > > numbers, etc.
> >
> > ??? I want a function that returns t only for a character
> > that require preceding LRM in the keyboard layout.
> Yes, I understand that. But the test you are suggesting, i.e. avoid
> the LRM only for characters whose bidi-class is L, will not catch
> numbers, punctuation, and other non-L characters.
The function body I wrote is just an idea, not a complete
solution, and of cource checking against L is apparently
a bug. At least we must check against R (and AL).
> > > Also, `lower' and `upper' could be strings, in which case you need a
> > > more complex test.
> >
> > We can give (if (string lower) (aref lower 0) lower) to that
> > function.
> But that doesn't DTRT. Here's an example where it will fail: ".A".
Why? Keyboard cells in the keyboard layout has typically
this form: (L is for lower key, U is for upper (shifted) key)
... | LU | LU | ...
What we want is to display the left LU to the left of the
right LU, and display each L (character or string) to the
right of the corresponding U.
Even if the L (of the left LU) is ".A", we don't need LRM
for it. We have to insert LRM only before a character that
may reorder the previous characters, and after a character that
may reorder the following character. Isn't it right?
> AFAIK, the only reliable way of telling whether a given string will be
> reordered is to actually reorder it, and then compare with the
> logical-order original. That's a nuisance, and also the results may
> well depend on the characters before and after the string in the
> buffer, so you need to know the context in advance, which you normally
> don't.
> I tried also a different solution: enclose each row of the keyboard
> layout in an L2R override embedding, LRO..PDF. This inserts only 2
> control characters per row, and doesn't insert them inside the
> keyboard cells, so it is cleaner, I think. But using this means that
> no key description in the layout can be a string that requires
> reordering individually. (By contrast, inserting an LRM between the
> lower and the upper key still allows each description to be
> reordered.) Can we live with such a restriction? I don't know enough
> about Quail to tell.
As it's possible to assign a string to a key, there will be
the case that the characters in the string must be
reordered. In the above case, if L is a hebrew "שלום", it
must be reordered. But, even if we surround that word with
LRE and PDF, the word itself is reordered correctly, right?
---
Kenichi Handa
handa@m17n.org
next prev parent reply other threads:[~2012-03-10 2:55 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-03-06 22:17 bidi and shaping problems in describe-input-method Mohsen BANAN
2012-03-07 4:05 ` Eli Zaretskii
2012-03-07 18:49 ` Eli Zaretskii
2012-03-07 21:32 ` Mohsen BANAN
2012-03-08 15:30 ` Kenichi Handa
2012-03-08 18:24 ` Eli Zaretskii
2012-03-08 23:48 ` Kenichi Handa
2012-03-09 8:11 ` Eli Zaretskii
2012-03-09 14:03 ` Kenichi Handa
2012-03-09 16:12 ` Eli Zaretskii
2012-03-10 2:55 ` Kenichi Handa [this message]
2012-03-10 10:27 ` Eli Zaretskii
2012-03-12 7:47 ` Kenichi Handa
2012-03-12 17:42 ` Eli Zaretskii
2012-03-13 0:58 ` Kenichi Handa
2012-03-13 3:58 ` Eli Zaretskii
2012-03-22 4:26 ` Kenichi Handa
2012-03-22 17:23 ` Eli Zaretskii
2012-03-23 1:41 ` Kenichi Handa
2012-03-23 10:12 ` Eli Zaretskii
2012-03-22 21:59 ` Mohsen BANAN
2012-03-13 5:46 ` Mohsen BANAN
2012-03-09 8:17 ` Eli Zaretskii
2012-03-08 18:30 ` Eli Zaretskii
2012-03-08 18:53 ` Eli Zaretskii
2012-03-08 23:27 ` Kenichi Handa
2012-03-08 23:19 ` Kenichi Handa
2012-03-09 8:15 ` Eli Zaretskii
2012-03-09 9:01 ` Juanma Barranquero
2012-03-09 9:45 ` Eli Zaretskii
2012-03-09 10:02 ` Eli Zaretskii
2012-03-09 14:11 ` Kenichi Handa
2012-03-09 11:19 ` Juanma Barranquero
2012-03-09 11:41 ` Eli Zaretskii
2012-03-09 14:56 ` Juanma Barranquero
2012-03-09 13:54 ` Kenichi Handa
2012-03-09 16:15 ` Eli Zaretskii
2012-03-08 4:30 ` Miles Bader
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
List information: https://www.gnu.org/software/emacs/
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=87r4x1uptx.fsf@m17n.org \
--to=handa@m17n.org \
--cc=eliz@gnu.org \
--cc=emacs-devel@gnu.org \
--cc=list-general@mohsen.1.banan.byname.net \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
Code repositories for project(s) associated with this public inbox
https://git.savannah.gnu.org/cgit/emacs.git
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).