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From: Nicolas Goaziou <mail@nicolasgoaziou.fr>
To: Eli Zaretskii <eliz@gnu.org>
Cc: Shingo Tanaka <shingo.fg8@gmail.com>, 48148@debbugs.gnu.org
Subject: bug#48148: 27.2; ox-ascii breaks TITLE line wrongly when 2 width char is used
Date: Sun, 02 May 2021 10:23:34 +0200	[thread overview]
Message-ID: <87h7jla6ih.fsf@nicolasgoaziou.fr> (raw)
In-Reply-To: <83bl9t8vnb.fsf@gnu.org> (Eli Zaretskii's message of "Sun, 02 May 2021 10:03:36 +0300")

Hello,

Eli Zaretskii <eliz@gnu.org> writes:

>> Date: Sun, 02 May 2021 08:52:13 +0900
>> From: Shingo Tanaka <shingo.fg8@gmail.com>
>> 
>> For example, when the title is "ABCDEF" (each character has width of
>> 2), expected title would be like:
>> 
>>                      ━━━━━━━━━━━━━━━
>>                               ABCDEF
>>                      ━━━━━━━━━━━━━━━
>> 
>> However, the reality is:
>> 
>>                      ━━━━━━━━━━━━━━━
>>                                  ABC
>>                                  DEF
>>                      ━━━━━━━━━━━━━━━
>>                      
>> This is because it uses `length' to detects the width, which only returns the
>> number of characters (6 in this case) but not the actual width displayed (12
>> in this case), and it tries to fill the line with that half width.
>> `string-width' should be used instead.
>> 
>> Here is a potential patch.
>> 
>> --- ox-ascii.el.org	2021-03-26 09:28:44.000000000 +0900
>> +++ ox-ascii.el	2021-05-02 08:11:57.657347150 +0900
>> @@ -1033,7 +1033,7 @@
>>  	     ;; Format TITLE.  It may be filled if it is too wide,
>>  	     ;; that is wider than the two thirds of the total width.
>>  	     (title-len (min (apply #'max
>> -				    (mapcar #'length
>> +				    (mapcar #'string-width
>>  					    (org-split-string
>>  					     (concat title "\n" subtitle) "\n")))
>>  			     (/ (* 2 text-width) 3)))
>
> Thanks, but the change you propose will not work reliably on GUI
> frames, because the actual width of double-width characters on display
> is not necessarily twice the width of a "normal" character.
> Especially if this is done in a non-CJK locale, where the default font
> is likely to be different from the font used for double-width
> characters.
>
> The accurate method of lining up in these cases is to use
> window-text-pixel-size instead.  That function will return the exact
> width of a string as it will displayed, in pixels, because it uses the
> same code as the display engine.

Would you mind giving an example about `window-text-pixel-size' usage in
this situation?

AFAIU, `window-text-pixel-size' returns the size of the window, but
I fail to see how it is relevant here. Note that `text-width' in the
code above is not related to the width of the window, but is a maximum
number of allowed characters on a line.

Thank you!

Regards,
-- 
Nicolas Goaziou




  reply	other threads:[~2021-05-02  8:24 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <87h7jm2es2.wl-shingo.fg8@gmail.com>
2021-05-02  7:03 ` Eli Zaretskii
2021-05-02  8:23   ` Nicolas Goaziou [this message]
2021-05-02  9:11     ` Eli Zaretskii
2021-05-02 11:33       ` Shingo Tanaka
2021-05-02 12:43         ` Eli Zaretskii
2021-05-02 12:18       ` Nicolas Goaziou
2021-05-02 12:48         ` Eli Zaretskii
2021-05-02 15:56           ` Nicolas Goaziou
2021-05-02 16:11             ` Eli Zaretskii

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