bug#19395: 25.0.50; Setting left fringe to 0 messes up window-width

[Eli Zaretskii]

> Date: Sat, 20 Dec 2014 11:09:18 +0100
> From: martin rudalics <rudalics@gmx.at>
> CC: malsburg@posteo.de, 19395@debbugs.gnu.org
> 
>  > I don't think the results of font-info depend on that.  It's the
>  > result of face-font that depend on the buffer and frame, but once you
>  > have the font's name, all the rest doesn't matter, since Emacs already
>  > have the font data structure set up and stored in memory.
> 
> Then we should mention the buffer for `face-font'.

I agree.  Feel free to add that (and please mention face remapping, as
I believe it is the only reason why the buffer, as opposed to the
frame, could be relevant).

> BTW, why does the Elisp manual say that it does "mostly provide
> compatibility with old versions of Emacs"?

AFAIU, it only says so about the set-face-FOO functions, which doesn't
include face-font.

> But we also should mention (and I still think `font-info' is the better
> place for that) what happens when the current buffer has rescaled text
> but is not displayed on the selected frame (or the frame denoted by the
> argument of `font-info').

How can the current buffer be not displayed in the selected frame?

> I would do that myself but I got lost in the code.  I still don't
> understand where and how text rescaling is applied.

In face-remap.el, and then in xfaces.c (search for face_remapping in
the latter).  Assuming I understand correctly what is it that confused
you.