Re: [PATCH] prompt: support generic non-visible regions

[Mikael Magnusson <mikachu@gmail.com>]

On 8/10/22, Felipe Contreras <felipe.contreras@gmail.com> wrote:
> On Wed, Aug 10, 2022 at 1:59 PM Mikael Magnusson <mikachu@gmail.com> wrote:
>>
>> On 8/10/22, Felipe Contreras <felipe.contreras@gmail.com> wrote:
>> > readline assumes anything between \001 (start of header) and \002
>> > (start
>> > of text) is non-visible characters.
>> >
>> > In zsh we do this with `%F{color}`, but we could support
>> > `\001\e[31m\002` as well.
>> >
>> > Signed-off-by: Felipe Contreras <felipe.contreras@gmail.com>
>> > ---
>> >
>> > I don't know if this is the right way to do it, but in my limited
>> > testing it seems to work fine.
>>
>> The commit message seems a bit confused, %F has nothing to do with
>> marking characters as 0-width, rather everything between %{ and %}
>> will be treated as such. You can use %{%} (or \001 and \002) to set
>> colors via the specific \e [ Ps m code, but also to send any other
>> codes handled by the terminal.
>
> If I do PS1='%F{red}foo' putpromptchar() will call
> set_colour_attribute(), which eventually calls this:
>
>   if (!bv->dontcount) {
>       addbufspc(1);
>       *bv->bp++ = Inpar;
>   }
>   tputs(tgoto(tcstr[tc], colour, colour), 1, putstr);
>   if (!bv->dontcount) {
>       addbufspc(1);
>       *bv->bp++ = Outpar;
>   }
>
> I can do the same thing fputs() is doing with PS1=$'\e[31mfoo', but
> now zsh will think my prompt is bigger than it actually is and the
> shell will be screwed. So I have to put that inside %{%}.
>
> Therefore "%F{red}" = $'%{\e[31m%}'

Sure, this agrees 100% with what I was saying, but the statement in
the commit still doesn't make sense. You've proven that you can use %{
or \001 to do what %F{} does, but the commit message states the
opposite which is not true.

>> That aside, I don't really see a reason to add support for
>> bash-specific prompt sequences that are more cumbersome to use than
>> the already existing zsh ones. Bash prompts are already completely
>> incompatible anyway.
>
> The prompts are not compatible, but the functions used in those prompts can
> be.
>
>   __git_ps1_test () {
>     local branch='master'
>     local red=$'\001\e[31m\002'
>     local clear=$'\001\e[m\002'
>     echo "${red}${branch}${clear}"
>   }
>
> The function above works perfectly fine in bash and zsh with my patch,
> and I can add $(__git_ps1_test) to both of my prompts.

You could also have a $START_INVIS and $END_INVIS parameter depending
on what shell you're in. Well, I don't have a strong opinion either
way, but it doesn't seem worth it to me. If we support this, people
might ask "but you support \001, why not this other xyz prompt feature
from bash?"

-- 
Mikael Magnusson