bug#39245: 26.3; 'mouse-face highlighting is extended beyond EOB

[ynyaaa]

If a buffer does not end with a newline and 'mouse-face property is
added at the last character, 'mouse-face highlighting covers the blank
area to the right of the last character.

If 'mouse-face region contains newline characters,
the blank area to the right of the last character is not highlighted.

Example: Evaluate the form below and move the mouse pointer onto 'XYZ'.
Then the blank area to the right of 'Z' is highlighted.
If a newline character is inserted between 'X' and 'Y',
the blank area to the right of 'Z' is not highlighted.

  (let ((buf (generate-new-buffer "tmp")))
    (switch-to-buffer buf)
    (insert (propertize "XYZ" 'mouse-face 'region)))


In GNU Emacs 26.3 (build 1, x86_64-w64-mingw32)
 of 2019-08-29 built on CIRROCUMULUS
Repository revision: 96dd0196c28bc36779584e47fffcca433c9309cd
Windowing system distributor 'Microsoft Corp.', version 10.0.18363
Recent messages:

Configured using:
 'configure --without-dbus --host=x86_64-w64-mingw32
 --without-compress-install 'CFLAGS=-O2 -static -g3''

Configured features:
XPM JPEG TIFF GIF PNG RSVG SOUND NOTIFY ACL GNUTLS LIBXML2 ZLIB
TOOLKIT_SCROLL_BARS THREADS LCMS2

Important settings:
  value of $LANG: JPN
  locale-coding-system: cp932

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 emacsbug mailalias smtpmail sendmail sort mail-extr message
dired dired-loaddefs rfc822 mml mml-sec epa derived epg epg-config
mm-decode mm-bodies mm-encode mailabbrev gmm-utils mailheader help-fns
radix-tree pp descr-text cl-extra help-mode network-stream starttls
url-http tls gnutls mail-parse rfc2231 url-gw nsm rmc url-cache url-auth
eww easymenu puny mm-url gnus nnheader gnus-util rmail rmail-loaddefs
rfc2047 rfc2045 ietf-drums mail-utils wid-edit mm-util mail-prsvr
url-queue url url-proxy url-privacy url-expand url-methods url-history
url-cookie url-domsuf url-util url-parse auth-source cl-seq eieio
eieio-core cl-macs eieio-loaddefs password-cache url-vars mailcap shr
svg xml seq byte-opt gv bytecomp byte-compile cconv dom browse-url
format-spec cl-loaddefs cl-lib elec-pair time-date mule-util japan-util
tooltip eldoc electric uniquify ediff-hook vc-hooks lisp-float-type
mwheel dos-w32 ls-lisp disp-table term/w32-win w32-win w32-vars
term/common-win 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 threads w32notify w32 lcms2 multi-tty make-network-process
emacs)

Memory information:
((conses 16 161708 174502)
 (symbols 48 49361 1)
 (miscs 40 54 395)
 (strings 32 109842 2812)
 (string-bytes 1 2498276)
 (vectors 16 24952)
 (vector-slots 8 1685746 190664)
 (floats 8 79 505)
 (intervals 56 14250 4622)
 (buffers 992 15))