bug#64420: string-width of … is 2 in CJK environments

[Dmitry Gutov <dmitry@gutov.dev>]

On 13/08/2023 08:24, Eli Zaretskii wrote:
>> Date: Sun, 13 Aug 2023 03:22:41 +0300
>> Cc:itaemu@gmail.com,64420@debbugs.gnu.org
>> From: Dmitry Gutov<dmitry@gutov.dev>
>>
>> On 11/08/2023 21:07, Yuan Fu wrote:
>>> On GUI display, the later-half of the ambiguous characters are definitely wider than one char, but they aren’t quite 2 chars wide either. But I guess it doesn’t matter too much since one should use pixel size on GUI anyway.
>> BTW, I think most double-width characters on GUI are less than 2
>> characters wide?
>>
>> So the point here would be that some "ambiguous" ones are still wider
>> than 1, I guess.
> According to Yuan, at least in his environment those characters have a
> width that is closer to 2 than to 1.  In which case using 2 would
> produce better alignment.  Of course, using string-pixel-width will
> produce an even better alignment.

In GUI, that is. But if they are displayed with width 1 in terminal, we 
better make string-width return 1 for them too.

That might be slightly worse for certain applications (like popup in 
company), but at least the basic rendering and navigation bugs in 
terminal will be fixed this way. And the new popup rendering for company 
(using string-width and spacing instructions) is close to being ready 
anyway.