bug#37880: 27.0.50; Changing font size in Info-mode messes up formatting

[Stefan Monnier via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>]

Lars Ingebrigtsen [2022-05-07 14:07:24] wrote:
> Stefan Monnier <monnier@iro.umontreal.ca> writes:
>> So, I'd like to extend our `space` specifications so as to be able to
>> specify a minimum width.  I came up with the patch below which lets you
>> write:
>>
>>     (space :align-to FOO :min-width BAR)
>>
>> which seems to work fine, but while trying to update the Elisp doc for
>> it I realized that maybe a better option is to extend the acceptable
>> forms for FOO so it can be of the form:
>>
>>     (space :align-to (max FOO (+ BAR current-x)))
>
> I think I'd actually prefer the first form -- it's easy to reason about,
> and does what most usage cases want (i.e., align if possible, but if
> not, then at least leave some space so that things don't run into each
> other).

The patch I came up with back then doesn't work right.  IIRC it's
because we need to change both the redisplay code and the
`current-column` code and it only changed one of the two.

IIRC, I decided then that the right fix is to rewrite the
`current-column` code to use the redisplay code (instead of trying to
mimic it), but I didn't get around to that (and IIRC it's not
completely straightforward because `current-column` currently behaves
differently *on purpose* in some cases (most importantly w.r.t treating
ellipsis-erased text) so fixing it right will imply changes in behavior
and figuring out how to do it without breaking existing uses).


        Stefan