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From: Yuan Fu <casouri@gmail.com>
To: Eli Zaretskii <eliz@gnu.org>
Cc: Lars Ingebrigtsen <larsi@gnus.org>, emacs-devel <emacs-devel@gnu.org>
Subject: Re: Line wrap reconsidered
Date: Sun, 31 May 2020 13:39:56 -0400	[thread overview]
Message-ID: <C8526F78-4A2F-466B-88F7-D57B34035635@gmail.com> (raw)
In-Reply-To: <83blm6lzj3.fsf@gnu.org>



> On May 30, 2020, at 2:14 AM, Eli Zaretskii <eliz@gnu.org> wrote:
> 
>> From: Yuan Fu <casouri@gmail.com>
>> Date: Fri, 29 May 2020 17:20:21 -0400
>> Cc: Lars Ingebrigtsen <larsi@gnus.org>,
>> emacs-devel@gnu.org
>> 
>>> Then you'll need to augment the test
>>> 
>>> else if (may_wrap)
>>> 
>>> with a test that the current character can be at BOL.  Maybe you
>>> should also make may_wrap a tristate instead of just a boolean YES/NO.
>>> 
>> 
>> I think I did jus that, i.e., if (may_wrap && char_can_wrap_before(it)).
> 
> Fundamentally, yes.  But having a complex condition
> 
>   if (FOO && BAR)
> 
> makes the code harder to read and understand, and thus makes logical
> errors easier, than a simple condition like
> 
>   if (FOOBAR == some_value)

In principle, yes, but I doubt the current logic can be simplified. Do you have some concrete example?

> 
>>>> Essentially I want to ask “if may_wrap == true, what does that mean? (In bidi context)” Did the character to the left of me (on glass) set it or the character to the right of me set it?
>>> 
>>> The one to the left.  But it is not necessarily the "previous"
>>> character in buffer position order.
>> 
>> I see, but then I don’t don’t understand how does the current code work with bidi display. In bidi context, space char can’t appear on the right of the line, which is the beginning of a logic line, right? That requires the logic to reverse. Is there something I’m missing?
> 
> I think the cause of the confusion is the "in bidi context" part.
> There are two such "contexts", and they behave differently:
> 
> . RTL characters when bidi-paragraph-direction is left-to-right
> . RTL characters when bidi-paragraph-direction is right-to-left
> 
> Which one were you talking about?  I was talking about the first one.
> 
>> Since may_wrap’s meaning is in terms of left and right, it need to be reversed in bidi text, no?
> 
> If bidi-paragraph-direction is right-to-left, then yes, they are
> reversed.  But not if the paragraph direction is left-to-right.

Then does bidi.c handle word wrapping when bidi-paragraph-direction is right-to-left? Paragraph 3.4 mentioned that “The accumulated widths of those glyphs (in logical order) are used to determine line breaks.”

> 
>> One more question. If I type 123456789... and set bidi-paragraph-direction to ‘right-to-left, it is still 123456789…, just aligned to the right. I expected to see …987654321, that’s what right-to-left mean in Chinese text. Why the order of each character not revered?
> 
> Digits and LTR characters (like English text) are rendered
> left-to-right even in RTL paragraphs, so what you see is correct.
> That's why this is called "bidirectional": the direction is not just
> universally right-to-left.

I see, so characters have their inherited order and that never changes, only paragraphs change orders. 

> 
>> UAX#9 didn’t say anything helpful.
> 
> It does, albeit in a convoluted and hard-to-grasp way.  See paragraph
> 3.3.6 there, and then rule L2 in paragraph 3.4, which describes the
> reordering procedure.

Thanks.

Yuan




  reply	other threads:[~2020-05-31 17:39 UTC|newest]

Thread overview: 88+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-25 18:13 Line wrap reconsidered Yuan Fu
2020-05-25 19:23 ` Eli Zaretskii
2020-05-25 19:31   ` Yuan Fu
2020-05-26  1:55   ` Ihor Radchenko
2020-05-26 12:55     ` Joost Kremers
2020-05-26 13:35       ` Yuan Fu
2020-05-26 14:47     ` Eli Zaretskii
2020-05-26 15:01       ` Ihor Radchenko
2020-05-26 15:29         ` Eli Zaretskii
2020-05-26 15:46           ` Ihor Radchenko
2020-05-26 16:29             ` Eli Zaretskii
2020-05-26 15:59       ` Stefan Monnier
2020-05-26 16:31         ` Eli Zaretskii
2020-05-26 16:43           ` Yuan Fu
2020-05-26 16:43             ` Ihor Radchenko
2020-05-26 18:57             ` Eli Zaretskii
2020-05-26 19:10               ` Yuan Fu
2020-05-26 19:59                 ` Eli Zaretskii
2020-05-26 19:12               ` Ihor Radchenko
2020-05-26 20:04                 ` Eli Zaretskii
2020-05-26 21:01                   ` Stefan Monnier
2020-05-25 19:31 ` Stefan Monnier
2020-05-25 19:51   ` Yuan Fu
2020-05-25 20:43 ` Lars Ingebrigtsen
2020-05-25 23:26   ` Yuan Fu
2020-05-25 23:32     ` Yuan Fu
2020-05-26  2:15       ` Yuan Fu
2020-05-26  3:30         ` Yuan Fu
2020-05-26  4:46           ` Yuan Fu
2020-05-26 15:14             ` Eli Zaretskii
2020-05-26 15:00           ` Eli Zaretskii
2020-05-26 14:54       ` Eli Zaretskii
2020-05-26 17:34         ` Yuan Fu
2020-05-26 19:50           ` Eli Zaretskii
2020-05-26 20:31             ` Yuan Fu
2020-05-26 22:29               ` Yuan Fu
2020-05-27 17:29                 ` Eli Zaretskii
2020-05-28 17:31                   ` Yuan Fu
2020-05-28 18:05                     ` Eli Zaretskii
2020-05-28 19:34                       ` Yuan Fu
2020-05-28 20:42                         ` Yuan Fu
2020-05-29  7:17                           ` Eli Zaretskii
2020-05-29  6:56                         ` Eli Zaretskii
2020-05-29 21:20                           ` Yuan Fu
2020-05-30  6:14                             ` Eli Zaretskii
2020-05-31 17:39                               ` Yuan Fu [this message]
2020-05-31 17:55                                 ` Eli Zaretskii
2020-05-31 18:23                                   ` Yuan Fu
2020-05-31 18:47                                     ` Eli Zaretskii
2020-06-18 21:46                                       ` Yuan Fu
2020-06-19  6:17                                         ` Eli Zaretskii
2020-06-19 12:04                                           ` Yuan Fu
2020-06-19 12:38                                             ` Eli Zaretskii
2020-06-19 17:22                                               ` Yuan Fu
2020-06-19 17:47                                                 ` Eli Zaretskii
2020-06-19 18:03                                                   ` Yuan Fu
2020-06-19 18:34                                                     ` Eli Zaretskii
2020-07-12 17:25                                                       ` Yuan Fu
2020-07-12 18:27                                                         ` Eli Zaretskii
2020-07-12 19:28                                                           ` Yuan Fu
2020-07-13 19:46                                                             ` Yuan Fu
2020-07-18  8:15                                                               ` Eli Zaretskii
2020-07-18 17:14                                                                 ` Yuan Fu
2020-07-18 19:49                                                                   ` Yuan Fu
2020-07-18 20:25                                                                   ` Stefan Monnier
2020-07-19 14:52                                                                   ` Eli Zaretskii
2020-07-19 16:16                                                                     ` Yuan Fu
2020-07-19 16:17                                                                       ` Yuan Fu
2020-08-13 19:35                                                                         ` Yuan Fu
2020-08-14  5:55                                                                           ` Eli Zaretskii
2020-08-14 15:08                                                                             ` Yuan Fu
2020-08-15  9:10                                                                               ` Eli Zaretskii
2020-08-15 13:10                                                                                 ` Fu Yuan
2020-08-15 14:56                                                                                   ` Eli Zaretskii
2020-08-15 17:34                                                                                     ` Yuan Fu
2020-08-15 17:46                                                                                       ` Eli Zaretskii
2020-08-15 18:00                                                                                         ` Yuan Fu
2020-08-15 18:47                                                                                           ` Eli Zaretskii
2020-08-16  3:22                                                                                             ` Yuan Fu
2020-08-16 14:15                                                                                               ` Eli Zaretskii
2020-08-16 17:31                                                                                                 ` Yuan Fu
2020-08-22  7:42                                                                                                   ` Eli Zaretskii
2020-08-22 20:58                                                                                                     ` Yuan Fu
2020-08-23  7:12                                                                                                       ` Eli Zaretskii
2020-08-24 14:00                                                                                                         ` Yuan Fu
2020-05-27 15:20               ` Eli Zaretskii
2020-05-26  8:02 ` martin rudalics
2020-05-26 12:38   ` Yuan Fu

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