Re: Invisible PROMPT2

Kyotaro Horiguchi <horikyota(dot)ntt(at)gmail(dot)com> writes:
> This seems assuming %x are a kind of stable (until semicolon)
> function. But at least %`..` can be volatile. So, I think the %w
> thing in PROMPT2 should be able to refer the actual prompt string
> resulted from PROMPT1.

Oh, that's a good point. But it actually leads to a much simpler
definition and implementation than the other ideas we've kicked
around: define %w as "whitespace equal to the length of the
last-generated PROMPT1 string (initially empty)", and we just
have to save PROMPT1 each time we generate it.

Except ... I'm not sure how to deal with hidden escape sequences.
We should probably assume that anything inside %[...%] has width
zero, but how would we remember that?

Maybe count the width of non-escape characters whenever we
generate PROMPT1, and just save that number not the string?
It'd add overhead that's useless when there's no %w, but
probably not enough to care about.

regards, tom lane