GNU bug report logs - #76852
30.1; Regression in whitespace-mode causes display issue under terminal

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From: help-debbugs <at> gnu.org (GNU bug Tracking System)
To: 张海 <dreaming.in.code.zh <at> gmail.com>
Subject: bug#76852: closed (Re: bug#76852: 30.1; Regression in
 whitespace-mode causes display issue under terminal)
Date: Sat, 29 Mar 2025 11:21:02 +0000

[Message part 1 (text/plain, inline)]

Your bug report

#76852: 30.1; Regression in whitespace-mode causes display issue under terminal

which was filed against the emacs package, has been closed.

The explanation is attached below, along with your original report.
If you require more details, please reply to 76852 <at> debbugs.gnu.org.

-- 
76852: https://debbugs.gnu.org/cgi/bugreport.cgi?bug=76852
GNU Bug Tracking System
Contact help-debbugs <at> gnu.org with problems

[Message part 2 (message/rfc822, inline)]

From: Eli Zaretskii <eliz <at> gnu.org>
To: dreaming.in.code.zh <at> gmail.com
Cc: 76852-done <at> debbugs.gnu.org
Subject: Re: bug#76852: 30.1;
 Regression in whitespace-mode causes display issue under terminal
Date: Sat, 29 Mar 2025 14:19:54 +0300

> Cc: 76852 <at> debbugs.gnu.org
> Date: Sat, 15 Mar 2025 13:45:27 +0200
> From: Eli Zaretskii <eliz <at> gnu.org>
> 
> > Cc: 76852 <at> debbugs.gnu.org
> > Date: Thu, 13 Mar 2025 16:11:35 +0200
> > From: Eli Zaretskii <eliz <at> gnu.org>
> > 
> > > From: 张海 <dreaming.in.code.zh <at> gmail.com>
> > > Date: Thu, 13 Mar 2025 02:32:33 -0700
> > > Cc: 76852 <at> debbugs.gnu.org
> > > 
> > > > Currently, the two solution I'm pondering are:
> > > >
> > > >   . remove from the list of ambiguous-width characters some of the
> > > >     characters with low Unicode codepoints, including the 2 characters
> > > >     used by whitespace-mode, on the assumption that these characters
> > > >     are unlikely to be full-width in fonts used by Emacs users in CJK
> > > >     locales
> > > 
> > > I wonder how emacs 29.4 dealt with this - did it also have a special
> > > list of characters that it treats as half-width, while the rest are
> > > treated as full-width like what was in the announcement?
> > 
> > Emacs 29 didn't have the notion of ambiguous-width characters.  Each
> > character was either a half-width or a full-width.  And the characters
> > used by whitespace-mode were half-width.
> > 
> > > >   . change the default of cjk-ambiguous-chars-are-wide to nil, on
> > > >     the assumption that most users in CJK locales use fonts where
> > > >     these characters have half-width glyphs
> > > 
> > > I think this might be a good option because both TTY and some popular
> > > terminal emulators like gnome-terminal, gnome-console and foot ship
> > > with the ambiguous CJK characters defaulted to half width.
> > 
> > Yes, but are we sure that users in CJK locales don't customize
> > terminal emulators to default the ambiguous-width characters to
> > full-width?  If many users do that, then Emacs should cater to the
> > majority.
> > 
> > > > Thanks.  Let me think a bit more about what would be the best
> > > > solution.  But could you tell which font you used that has full-width
> > > > glyphs for these characters?  Is it unusual to use that font for
> > > > terminal emulators in CJK locales?
> > > 
> > > The fonts I'm using, and most Chinese Linux users may be using (to my
> > > understanding), are:
> > > - WenQuanYi (WQY) fonts
> > > - Noto (i.e. Source Han, a different branding) fonts
> > > See also https://wiki.archlinux.org/title/Localization/Chinese
> > > 
> > > The WenQuanYi fonts have a much longer history and the middle dot is
> > > always half width in them (checked just now). I'm currently using
> > > WenQuanYi Micro Hei.
> > > 
> > > The Noto/Source Han fonts are relatively new and have an interesting
> > > situation where the Noto Sans CJK SC/TC have the middle dot as full
> > > width but Noto Sans CJK JP/KR have it as half width.
> > > 
> > > Some Microsoft proprietary system-default fonts for Chinese
> > > characters, e.g. SimSun and SimHei, also have the middle dot as full
> > > width, but I guess few Linux users would be using it.
> > > 
> > > I should also mention that some CJK users prepend an English font
> > > before their CJK font for usage in UI/terminal, because English fonts
> > > usually contain better quality glyphs for latin letters than the ones
> > > embedded in CJK fonts - essentially they only use the CJK-only part of
> > > the CJK fonts. So the middle dot will always be half width for them.
> > > 
> > > > I'm wondering why we didn't hear
> > > > by now complaints from CJK users about the effects of
> > > > cjk-ambiguous-chars-are-wide other than on whitespace-mode.  Maybe the
> > > > other ambiguous-width characters are seldom used in practice?  Or
> > > > maybe too little time has passed since Emacs 30 was released?
> > > 
> > > I think it could be both:
> > > 
> > > 1. Emacs 30 is still new-ish, e.g. it landed in Arch Linux stable on
> > > Feb 25, only two weeks ago
> > > 
> > > 2. Not a lot of CJK users set a CJK locale ($LANG) for their terminal
> > > - they usually set it for the DE but not necessarily in
> > > /etc/locale.conf for the entire environment, because that means
> > > localized messages won't appear properly under TTY with its default
> > > font. I did that because I would manually set LANG if I actually have
> > > to use TTY instead of a terminal emulator some day.
> > 
> > Thanks for the info, I will think about this some more.
> 
> I eventually decided to go with the more conservative approach of
> removing the two characters used by whitespace-mode from the list of
> ambiguous-width characters.
> 
> This change is not installed on the emacs-30 branch, so the next Emacs
> release should have this problem fixed.

The above should have said "This change is now installed on the
emacs-30 branch".

No further comments, so I presume the fix is okay, and I'm closing
this bug.

[Message part 3 (message/rfc822, inline)]

From: 张海 <dreaming.in.code.zh <at> gmail.com>
To: bug-gnu-emacs <at> gnu.org
Subject: 30.1;
 Regression in whitespace-mode causes display issue under terminal
Date: Fri, 7 Mar 2025 13:22:45 -0800

Hi Emacs maintainers,

I recently updated from Emacs 29.4 to 30.1 and noticed an issue when I
use global-whitespace-mode under terminal - each line would either
automatically wrap before reaching the right edge of the terminal, or
the cursor can go beyond the actual line end as if there were virtual
spaces. Inserting new characters also results in characters after the
insertion to drift right further than necessary and makes it
impossible to properly edit a document. The amount of drifting seems
to be related to the number of whitespace characters shown by
whitespace-mode. A image showing the bug is available at
https://imgur.com/a/PWbFgyE .

I verified that this issue occurs with `emacs -nw -q` (so that my
.emacs isn't interfering) and the `*scratch*` buffer (its vanilla
English-only content) using `M-x global-whitespace-mode` on Emacs 30.1
runnin under gnome-terminal, gnome-console and foot (the Wayland
terminal emulator) on most recent Arch Linux running GNOME 3 on
Wayland. My locale is zh_CN.UTF-8 and my terminal font, i.e. the
`monospace` font, is set to `WenQuanYi Micro Hei Mono` (文泉驿等宽微米黑 in
Chinese, part of the wqy-microhei Arch Linxu package), if that
matters. Downgrading to Emacs 29.4 immediately solved this issue so I
believe it is a regression.

Here's a screen recoding and the coresponding termscript of this issue:
- Video: https://imgur.com/a/IhA8JxD
- Termscript: https://files.catbox.moe/tskpy8

I've also attached some environment info and output from `M-x
report-emacs-bug` below, and hopefully they can be helpful in
debugging this.Thanks in advance!

Hai


TERM=xterm-256color
No /etc/termcap
LC_ALL= LC_COLLATE= LC_CTYPE= LC_MESSAGES= LC_TIME= LANG=zh_CN.UTF-8
fc-match monospace: wqy-microhei.ttc: "文泉驿等宽微米黑" "Regular"


In GNU Emacs 30.1 (build 2, x86_64-pc-linux-gnu, GTK+ Version 3.24.48,
cairo version 1.18.2)
Windowing system distributor 'The X.Org Foundation', version 11.0.12401006
System Description: Arch Linux

Configured using:
 'configure --with-x-toolkit=gtk3 --sysconfdir=/etc --prefix=/usr
 --libexecdir=/usr/lib --localstatedir=/var --disable-build-details
 --with-cairo --with-harfbuzz --with-libsystemd --with-modules
 --with-native-compilation=aot --with-tree-sitter 'CFLAGS=-march=x86-64
 -mtune=generic -O2 -pipe -fno-plt -fexceptions -Wp,-D_FORTIFY_SOURCE=3
 -Wformat -Werror=format-security -fstack-clash-protection
 -fcf-protection -fno-omit-frame-pointer -mno-omit-leaf-frame-pointer -g
 -ffile-prefix-map=/build/emacs/src=/usr/src/debug/emacs -flto=auto'
 'LDFLAGS=-Wl,-O1 -Wl,--sort-common -Wl,--as-needed -Wl,-z,relro
 -Wl,-z,now -Wl,-z,pack-relative-relocs -flto=auto''

Configured features:
ACL CAIRO DBUS FREETYPE GIF GLIB GMP GNUTLS GPM GSETTINGS HARFBUZZ JPEG
LCMS2 LIBOTF LIBSYSTEMD LIBXML2 M17N_FLT MODULES NATIVE_COMP NOTIFY
INOTIFY PDUMPER PNG RSVG SECCOMP SOUND SQLITE3 THREADS TIFF
TOOLKIT_SCROLL_BARS TREE_SITTER WEBP X11 XDBE XIM XINPUT2 XPM GTK3 ZLIB

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

Major mode: Fundamental

Minor modes in effect:
  global-whitespace-mode: t
  tooltip-mode: t
  global-eldoc-mode: t
  show-paren-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
  blink-cursor-mode: t
  minibuffer-regexp-mode: t
  buffer-read-only: t
  line-number-mode: t
  indent-tabs-mode: t
  transient-mark-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t

Load-path shadows:
None found.

Features:
(shadow sort mail-extr filecache compile comint ansi-osc ansi-color ring
comp-run bytecomp byte-compile comp-common rx emacsbug message mailcap
yank-media puny dired dired-loaddefs rfc822 mml mml-sec password-cache
epa derived epg rfc6068 epg-config gnus-util text-property-search
time-date subr-x mm-decode mm-bodies mm-encode mail-parse rfc2231
mailabbrev gmm-utils mailheader cl-loaddefs cl-lib sendmail rfc2047
rfc2045 ietf-drums mm-util mail-prsvr mail-utils cus-start cus-load
disp-table whitespace china-util rmc iso-transl tooltip cconv eldoc
paren electric uniquify ediff-hook vc-hooks lisp-float-type elisp-mode
mwheel term/x-win x-win term/common-win x-dnd touch-screen tool-bar dnd
fontset image regexp-opt fringe tabulated-list replace newcomment
text-mode lisp-mode prog-mode register page tab-bar menu-bar rfn-eshadow
isearch easymenu timer select scroll-bar mouse jit-lock font-lock syntax
font-core term/tty-colors frame minibuffer nadvice seq simple cl-generic
indonesian philippine 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 emoji-zwj charscript charprop case-table epa-hook
jka-cmpr-hook help abbrev obarray oclosure cl-preloaded button loaddefs
theme-loaddefs faces cus-face macroexp files window text-properties
overlay sha1 md5 base64 format env code-pages mule custom widget keymap
hashtable-print-readable backquote threads dbusbind inotify lcms2
dynamic-setting system-font-setting font-render-setting cairo gtk
x-toolkit xinput2 x multi-tty move-toolbar make-network-process
native-compile emacs)

Memory information:
((conses 16 81904 15452) (symbols 48 7904 0) (strings 32 19386 2345)
 (string-bytes 1 583198) (vectors 16 12555)
 (vector-slots 8 212422 11491) (floats 8 22 3) (intervals 56 411 13)
 (buffers 992 12))

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