[libvirt] [PATCH v3 1/3] vsh: Add API for printing tables.

[Simon Kobyda]

On Thu, 2018-08-16 at 12:28 +0100, Daniel P. Berrangé wrote:
> On Thu, Aug 16, 2018 at 12:56:24PM +0200, Simon Kobyda wrote:
> > 
> 
> After asking around I have found the right solution that we need to
> use
> for measuring string width.  mbstowcs()/wcswidth() will get the
> answer
> wrong wrt zero-width characters, combining characters, non-printable
> characters, etc. We need to use the libunistring library:
> 
>   
> https://www.gnu.org/software/libunistring/manual/libunistring.html#uniwidth_002eh
> 
> 
I've tried what you've suggested, but it seems that it doesn't work
well with all unicode characters. I'm looking into the code of the
library, and each function uN_strwidth calls function uN_width, and
that function calls uc_width for calculation of width of characters.
And if we look into the code of uc_width here:

http://git.savannah.gnu.org/gitweb/?p=gnulib.git;a=blob;f=lib/uniwidth/width.c;h=269cfc77f50a3b9802e5fb5620ff8bcf95e05e40;hb=HEAD#l415
it seems that this library is limited only to certain unicodes, e.g.:
hangul characters, angle brackets, CJK characters... But it doesn't
cover all multiple-width characters. Example: I try to throw any emoji
(e.g. 🙉, 🦀, 🏙), it returns width of 1 column for each charact
er, nevertheless these characters have width of 2 columns on terminal.

BTW, it seems unistring library imports those funcions from gnulib.

Simon Kobyda.