Eli Zaretskii <eliz@gnu.org> writes:

[...]

>> The result is even worse because now there is wrapping involved:
>
> This is not what I suggested.  I suggested to leave the spaces in the
> string intact and just put on each of them a display property whose
> value is '(space . (:width 1)).  This cannot possibly cause wrapping,
> unless the original string already does, because we don't change how
> many SPC characters are used, we just force each one of them to take
> exactly one canonical column.

Sorry, I did not understand that.  Do you mean something like this: