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



On 08/21/2018 11:18 AM, Simon Kobyda wrote:
> 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.

I guess the only option then is to try smartcols [1]. If it is good for
util-linux it's going to be good for us too. Although, I'd prefer to
have our own wrappers over their API.

https://github.com/karelzak/util-linux/tree/master/libsmartcols

Michal


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