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

[martin rudalics]

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

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').

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

martin