Re: UNICODE Private Use Area characters in BUFFER

[Mikael Magnusson <mikachu@xxxxxxxxx>]

On 10/23/22, Roman Perepelitsa <roman.perepelitsa@xxxxxxxxx> wrote:
> On Sun, Oct 23, 2022 at 6:29 PM Mikael Magnusson <mikachu@xxxxxxxxx> wrote:
>>
>> > Note: Private Use Area characters work fine everywhere else. For
>> > example,
>> > in PS1.
>>
>> I'm not sure we have any choice, we have to know how wide every
>> character we print is, and presumably there is no defined width for
>> them as the characters themselves are not defined.
>
> All terminals by default display characters from Private Use Area as
> narrow.

There is no reason to assume this to be the case though, since it is
explicitly unstandardized.

> Zsh also (correctly) treats them as narrow. For example, you
> can do this:
>
>     PS1=$'\uE0B0 '
>
> Whether your terminal can render this glyph or not, everything will
> work fine. The character will take one column and zsh will know that.

Whether or not the terminal uses 0, 1 or 2 spaces for the printed
character, it is okay that we print them assuming it uses 1 space,
since the user has access to the %{%}%G mechanisms to adjust for it in
prompts, this is not possible in the interactive buffer obviously.

> A few more tests to show that Private Use Area characters work find in
> zsh with the exception that you cannot put then in BUFFER:
>
>     % x=$'\uE0B0'
>
>     % print -r -- ${(m)#x}
>     1
>
>     % print -r -- ${${(%):-$x%1(l.at least 1 column.)}[2,-1]}
>     at least 1 column
>
>     % print -r --  ${${(%):-$x%2(l..less than 2 columns)}[2,-1]}
>     less than 2 columns

I or anyone else can make a terminal that does something else with
these codepoints. (I'm just pointing this out).

-- 
Mikael Magnusson