Subject: Re: [bug#65546] [PATCH v2] guix: Properly compute progress bar width.

From: Ludovic Courtès <[email-masked]>
Date: Wed, 11 Oct 2023 23:00:07 +0200

Hi Julien,

Julien Lepiller <[email-masked]> skribis:

> * guix/build/syscalls.scm (terminal-width): New procedure.
> * guix/progress.scm (progress-reporter/bar): Use it to compute progress
> bar width.
> * guix/git.scm (show-progress): Use it to compute progress bar width.
> * tests/syscalls.scm: Add tests.

Others have already said “LGTM”, and I concur.  I’ll still make a couple
of minor suggestions but that shoudln’t stop you from going ahead
(everyone’s waiting for it :-)).

> +(define get-wchar-ffi
> +  (pointer->procedure int
> +                      (dynamic-func "mbstowcs" (dynamic-link))
> +                      (list '* '* size_t)))
> +(define terminal-string-width-ffi
> +  (pointer->procedure int
> +                      (dynamic-func "wcswidth" (dynamic-link))
> +                      (list '* size_t)))
> +
> +(define (terminal-string-width str)
> +  "Return the width of a string as it would be printed on the terminal.  This
> +procedure accounts for characters that have a different width than 1, such as
> +CJK double-width characters."

I’d suggest following the style of the rest of the file, which is to do
something like:

(define terminal-string-width
  (let ((mbstowcs (syscall->procedure …))
        (wcswidth (syscall->procedure …)))
    (lambda (str)
      …)))

Ideally the syscalls.scm changes would be in a commit separate from the
progress.scm changes.

Now we have the problem that OpenJDK unfortunately depends on (guix
build syscalls), which makes this change half-of-the-world-rebuild.
There’s another pending syscalls.scm change:

  https://issues.guix.gnu.org/66055
  https://issues.guix.gnu.org/66054

Time to create a branch?

Ludo’.