Re: wcwidth and glibc 2.2

[Bruno Haible <haible@xxxxxxx>]

Markus Kuhn writes:

> Shouldn't GB18030 be upwards compatible with GBK and hence also use the
> CJK varirant of wcwidth()?

The wcwidth of GB18030 cannot be compatible with GB2312 and UTF-8
simultaneously. Given the structure of the encoding, I assumed
compatibility with UTF-8 is more important. Does anyone have a copy of
the GB18030 standard?

> > But your wcwidth_cjk() function needs more modifications. It differs
> > from the EUC-JP wcwidth in more than 200 values.
> 
> Thanks for your findings! This needs more investigation to distinguish
> the following three cases:
> 
>   a) http://www.unicode.org/Public/3.1-Update/EastAsianWidth-4d3.beta.txt
>      needs to be modified
> 
>   b) glibc EUC-JP wcwidth() needs to be modified
> 
>   c) the rules according to which I derived by wcwidth[_cjk]() from
>      the unicode.org data need to be modified

It's (c). CJK wcwidth must implement legacy behaviour. You cannot
assume that the unicode.org material will give the right answer here.

Bruno
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