bug#28605: 26.0.60; Part of leftmost character hidden

[Ola Nilsson]

Whenever I'm using two side-by-side windows, part of the leftmost
character in the right-side window is hidden. 

This is when I use the Gnome HiDPI window scaling set to 2 to make text
readable on my 4K screen.

The problem is visible with emacs -Q --no-x-resources.
Turing on display-line-numbers-mode hides the problem, at least with the
default settings.

To reproduce:
emacs -Q --no-x-resources
M-x split-window-right
toggle the hidpi window scaling between 1 and 2.

I'm trying to attach a screenshot.

/Ola

Screenshot from 2017-09-26 11-50-13.png
Description: screenshot

In GNU Emacs 26.0.60 (build 2, x86_64-pc-linux-gnu, GTK+ Version 3.14.5)
 of 2017-09-22 built on lnxolani1
Repository revision: d24ec5854098841388dfecf2c668e7f48f348af0
Windowing system distributor 'The X.Org Foundation', version 11.0.11604000
System Description:     Debian GNU/Linux 8.9 (jessie)

Recent messages:
For information about GNU Emacs and the GNU system, type C-h C-a.
Quit
Making completion list...

Configured using:
 'configure --prefix=/opt/emacs/26'

Configured features:
XPM JPEG TIFF GIF PNG RSVG IMAGEMAGICK SOUND GPM DBUS GSETTINGS NOTIFY
ACL LIBSELINUX GNUTLS LIBXML2 FREETYPE M17N_FLT LIBOTF XFT ZLIB
TOOLKIT_SCROLL_BARS GTK3 X11 LCMS2

Important settings:
  value of $LC_CTYPE: en_US.UTF-8
  value of $LANG: en_US.UTF-8
  locale-coding-system: utf-8-unix

Major mode: Lisp Interaction

Minor modes in effect:
  tooltip-mode: t
  global-eldoc-mode: t
  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

Load-path shadows:
None found.

Features:
(shadow sort mail-extr emacsbug message subr-x puny seq byte-opt gv
bytecomp byte-compile cconv cl-loaddefs cl-lib 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 elec-pair 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 replace newcomment
text-mode elisp-mode lisp-mode prog-mode register page menu-bar
rfn-eshadow isearch 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 composite charscript charprop
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 lcms2
dynamic-setting system-font-setting font-render-setting move-toolbar gtk
x-toolkit x multi-tty make-network-process emacs)

Memory information:
((conses 16 94980 7152)
 (symbols 48 20380 1)
 (miscs 40 42 118)
 (strings 32 28398 1362)
 (string-bytes 1 735822)
 (vectors 16 14036)
 (vector-slots 8 490291 11606)
 (floats 8 53 90)
 (intervals 56 216 0)
 (buffers 992 12)
 (heap 1024 29846 1215))