bug#36858: 27.0.50; display bugs with display-fill-column-indicator-mode

[Eli Zaretskii <eliz@gnu.org>]

> From: Carsten Dominik <carsten.dominik@gmail.com>
> Date: Sat, 10 Aug 2019 15:21:14 +0200
> Cc: Nicolas Goaziou <mail@nicolasgoaziou.fr>, rotim.davor@gmail.com, Ergus <spacibba@aol.com>, 
> 	36858@debbugs.gnu.org
> 
>  Can one of the Org developers (CC'ed) please tell why Org does this?
>  Why not limit the face to the actual text, and avoid putting the face
>  on the newline?
> 
> Because it looks good.  The begin/end lines delineate a block, and if you use a background color, then the
> color goes all across the window, which I think looks good and shows the structure better.

But that happens only if the face specifies a background color.  If it
specifies, say, :underline instead, on GUI frames it just extends one
character cell beyond the last character, and on TTY frames it goes to
the end of the window, i.e. behaves inconsistently.  And with
display-fill-column-indicator-mode turned on, on GUI frames it goes
half-way till the fill column: yet another inconsistent behavior.

So if you think the current display looks good, how about making it
optional?  Then this could be turned off to avoid the inconsistent
display in those use cases where it matters.