Re: changing the display of formfeed characters

[Eli Zaretskii <eliz@gnu.org>]

> From: Javier <invalid@invalid.invalid>
> Date: Fri, 31 Aug 2018 11:22:59 +0000 (UTC)
> 
> There are several suggested ways to display form feed (^L)
> 
> http://www.emacswiki.org/emacs/PageBreaks
> http://www.emacswiki.org/emacs/PrettyControlL
> https://www.emacswiki.org/emacs/pp-c-l.el
> http://ergoemacs.org/emacs/modernization_formfeed.html
> 
> However all them break whitespace-mode.  Is there a way to display
> formfeed ^L without interfering with whitespace-mode?
> 
> The issue has been known for long time.
> 
> http://lists.gnu.org/archive/html/help-gnu-emacs/2011-03/msg00891.html
> https://www.emacswiki.org/emacs/pp-c-l.el
> 
> Has somebody come with any idea how to display ^L in some way without
> breaking whitespace-mode?

AFAICT, those modes break whitespace-mode because they define their
own display table without copying the display table that was in effect
before the mode was switched on.  whitespace-mode does take care of
copying the previous display table, and doesn't override the way the
formfeed is displayed AFAICS.  So maybe activating those other modes
_before_ whitespace-mode will do the trick?  (Caveat: I didn't try
that.)

> Would it do the trick modifying the display table for ^L with a fixed width string?
> Like "=========" and avoiding to dynamically adjust for window width.

Not sure how this question is related, please elaborate.