Hi. Briefly, we’ve discussed this issue a little bit at UTC, and I’ve tried to engage terminal emulator vendors, who are who probably need to be part of the discussion.

I’m not sure about "Lack of explanation in the standard”, I think wording was added to make these updates out of scope.

I can try to dig up previous discussion if needed.

-s

--
Steven R. Loomis
Code Hive Tx, LLC
https://codehivetx.us
> On Sep 14, 2022, at 4:28 AM, Corentin via SG16 <sg16_at_[hidden]> wrote:
> 
> Hey folks.
> 
> How was the table of width in [format] derived? 
> http://eel.is/c++draft/format#string.std-12.sentence-3 <http://eel.is/c++draft/format#string.std-12.sentence-3>
> 
> We have 2 issues here: Lack of explanation in the standard makes it hard to evolve that table,
> and it does require maintenance as the Unicode standard evolves.
> 
> Reading the intent of https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2020/p1868r2.html <https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2020/p1868r2.html>,
> 
> We do want: 
> To treat 0-width codepoint as 1
> To treat emojis as 2
> To treat full width east asian as 2.  
> https://www.cl.cam.ac.uk/~mgk25/ucs/wcwidth.c <https://www.cl.cam.ac.uk/~mgk25/ucs/wcwidth.c> 
> 
> I think a better specification would be given that we have a floating reference to UAX44,
> to say that codepoints that have the Unicode property "Emoji_Presentation" or 
> East_Asian_Width="W"  have a width of 2.
> 
> This ensures implementation remains coherent as Unicode evolves.
> 
> Thanks, 
> Corentin
> 
> 
> 
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