emacs 25 choses fonts with different average width for 7x13 font, making
bold text take more horizontal space.  This is particularly a problem when
using themes like https://github.com/bbatsov/zenburn-emacs which use bold
to hihglight matching parenthesis in show-paren-mode, causing characters to
shift as the cursor is moved from a parenthesis to a non-parenthesis
character.

Repro that demonstrates the problem in both 25 pretest 1 and current head
(but is perfectly ok in emacs 24):

$ emacs -Q --eval '(progn (set-face-font '\''default "7x13") (print
(face-font "default")) (print (face-font "bold")))'

shows
  -misc-fixed-medium-r-normal--13-120-75-75-c-70-iso8859-1
  -misc-fixed-bold-r-normal--13-120-75-75-c-80-iso8859-1

Notice the jump from 70 to 80 before the iso8859 component - that's the
average width, and that's what I believe is causing bold characters to
render wider than non-bold ones.  Both are 70 in emacs 24.


Below is the diagnostics output from M-x report-emacs-bug:

In GNU Emacs 25.1.50.1 (x86_64-unknown-linux-gnu, X toolkit, Xaw3d scroll
bars)
 of 2016-02-22 built on alexk1
Repository revision: 81ef756e6aea369ec78f19b3609f01ceddc5851f
Windowing system distributor 'The X.Org Foundation', version 11.0.11501000
System Description: Ubuntu 14.04 LTS (upgraded from: Ubuntu 12.04.3 LTS)

Configured using:
 'configure --with-x-toolkit=lucid'

Configured features:
XAW3D XPM JPEG TIFF GIF PNG RSVG IMAGEMAGICK SOUND GPM DBUS GCONF
GSETTINGS NOTIFY GNUTLS LIBXML2 FREETYPE M17N_FLT LIBOTF XFT ZLIB
TOOLKIT_SCROLL_BARS LUCID X11

Important settings:
  value of $LANG: en_US.UTF-8
  value of $XMODIFIERS: @im=ibus
  locale-coding-system: utf-8-unix

Major mode: Lisp Interaction

Minor modes in effect:
  tooltip-mode: t
  global-eldoc-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  tool-bar-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  line-number-mode: t
  transient-mark-mode: t

Features:
(shadow sort mail-extr emacsbug message dired dired-loaddefs format-spec
rfc822 mml easymenu mml-sec password-cache epa derived epg epg-config
gnus-util rmail rmail-loaddefs mm-decode mm-bodies mm-encode mail-parse
rfc2231 mailabbrev gmm-utils mailheader sendmail rfc2047 rfc2045
ietf-drums mm-util mail-prsvr mail-utils time-date mule-util tooltip
eldoc electric uniquify ediff-hook vc-hooks lisp-float-type mwheel
term/x-win x-win term/common-win x-dnd tool-bar dnd fontset image
regexp-opt fringe tabulated-list newcomment elisp-mode lisp-mode
prog-mode register page menu-bar rfn-eshadow timer select scroll-bar
mouse jit-lock font-lock syntax facemenu font-core term/tty-colors frame
cl-generic cham georgian utf-8-lang misc-lang vietnamese tibetan thai
tai-viet lao korean japanese eucjp-ms cp51932 hebrew greek romanian
slovak czech european ethiopic indian cyrillic chinese charscript
case-table epa-hook jka-cmpr-hook help simple abbrev obarray minibuffer
cl-preloaded nadvice loaddefs button faces cus-face macroexp files
text-properties overlay sha1 md5 base64 format env code-pages mule
custom widget hashtable-print-readable backquote dbusbind inotify
dynamic-setting system-font-setting font-render-setting x-toolkit x
multi-tty make-network-process emacs)