Michael Heerdegen <michael_heerdegen@web.de> writes:

> when using completions-format -> vertical, and candidates are of quite
> different lengths, the *Completions* display is often clobbered.
>
> There are candidates put into a second columns although there is not
> enough horizontal space.
>
> And the last candidates are sometimes aligned to the nth column,
> while the first column is empty.
>
> Example for two columns:
>
> |a   a candidat|   ;; doesn't fit in column
> |xy  foo       |
> |gnu image     |
> |    bar       |   ;; strange
> |    emacs     |

This bug is still present in Emacs 28.  Way to reproduce it:

/src/emacs -geometry -0+0 -Q -eval "(setq completions-format 'vertical)"
M-x c<TAB><TAB><TAB>