Eli Zaretskii <eliz@HIDDEN>
to control <at> debbugs.gnu.org.
Full text available.Received: (at 79765) by debbugs.gnu.org; 8 Nov 2025 10:36:16 +0000 From debbugs-submit-bounces <at> debbugs.gnu.org Sat Nov 08 05:36:16 2025 Received: from localhost ([127.0.0.1]:50882 helo=debbugs.gnu.org) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from <debbugs-submit-bounces <at> debbugs.gnu.org>) id 1vHgIp-0007QF-NP for submit <at> debbugs.gnu.org; Sat, 08 Nov 2025 05:36:16 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:57256) by debbugs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.84_2) (envelope-from <eliz@HIDDEN>) id 1vHgIk-0007PX-Ha; Sat, 08 Nov 2025 05:36:14 -0500 Received: from fencepost.gnu.org ([2001:470:142:3::e]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from <eliz@HIDDEN>) id 1vHgId-0001BL-Ae; Sat, 08 Nov 2025 05:36:03 -0500 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=gnu.org; s=fencepost-gnu-org; h=MIME-version:References:Subject:In-Reply-To:To:From: Date; bh=QVMmWNm8zQoe5a9VBqRSOeN4nKOkE/wrb8aeSqsMmQ8=; b=jHFXlECNrXqA4zgcIRW7 K2xMJo5np5D6Tmwgep9ZkZIc139CqJsTyglt8EaYTFXhqj4f/zU0f1x8cjTxVmR3LsLnv1uJxpBvU U1bYf89dyitOQlfl5mUNYo+skoYEkV0j1Qfe2ksEYF4HsU8xgTnu7Rb0TkixpwmGn8tyGCiRjTroM n2IFFAEvo5929+4YLQF9lhjcPkW2pAMTbHdfYMAh+ivmW7kc4hyHcBtMvT1mGzpkTOuiCpYkd2f0B bgBlllQPMb6Q+CPg3KrNUYZR/TRnloZKRNTcjzzXS0rUEtM2dhWjWtb7WZP4UGPdqAfA5OV+dui9u 9AcZbCb8ca+8cw==; Date: Sat, 08 Nov 2025 12:35:59 +0200 Message-Id: <864ir495gw.fsf@HIDDEN> From: Eli Zaretskii <eliz@HIDDEN> To: Vincent Lefevre <vincent@HIDDEN>, Jared Finder <jared@HIDDEN> In-Reply-To: <87wm457et2.fsf@HIDDEN> (message from Vincent Lefevre on Tue, 04 Nov 2025 20:55:53 +0100) Subject: Re: bug#79765: 30.1; term/xterm.el does not set background-mode to 'light for light terminal backgrounds References: <87wm457et2.fsf@HIDDEN> MIME-version: 1.0 Content-type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit X-Spam-Score: -2.3 (--) X-Debbugs-Envelope-To: 79765 Cc: 79765 <at> debbugs.gnu.org X-BeenThere: debbugs-submit <at> debbugs.gnu.org X-Mailman-Version: 2.1.18 Precedence: list List-Id: <debbugs-submit.debbugs.gnu.org> List-Unsubscribe: <https://debbugs.gnu.org/cgi-bin/mailman/options/debbugs-submit>, <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=unsubscribe> List-Archive: <https://debbugs.gnu.org/cgi-bin/mailman/private/debbugs-submit/> List-Post: <mailto:debbugs-submit <at> debbugs.gnu.org> List-Help: <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=help> List-Subscribe: <https://debbugs.gnu.org/cgi-bin/mailman/listinfo/debbugs-submit>, <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=subscribe> Errors-To: debbugs-submit-bounces <at> debbugs.gnu.org Sender: "Debbugs-submit" <debbugs-submit-bounces <at> debbugs.gnu.org> X-Spam-Score: -3.3 (---) severity 79765 wishlist thanks > From: Vincent Lefevre <vincent@HIDDEN> > Date: Tue, 04 Nov 2025 20:55:53 +0100 > > > With "emacs -Q" in xterm and GNOME Terminal, both with > TERM=xterm-256color: > > (terminal-parameter nil 'background-mode) > > gives 'dark with a black background, but nil with a white background > instead of 'light as documented: Section 30.5 "Terminal Parameters" > of the Emacs Lisp (elisp) manual says > > ‘background-mode’ > The classification of the terminal's background color, either > ‘light’ or ‘dark’. > > The command > > printf '\e]11;?\e\\' > > in the terminal gives the correct response: > > 11;rgb:0000/0000/0000 with a black background; > 11;rgb:ffff/ffff/ffff with a white background. > > It appears that the background-mode terminal parameter is set by > lisp/term/xterm.el, which contains > > (defun xterm-maybe-set-dark-background-mode (redc greenc bluec) > ;; Use the heuristic in `frame-set-background-mode' to decide if a > ;; frame is dark. > (when (< (+ redc greenc bluec) (* .6 (+ 65535 65535 65535))) > (set-terminal-parameter nil 'background-mode 'dark) > t)) > > to set 'background-mode to 'dark, but there is nothing to set it > to 'light, and I think that this explains the current behavior. > > Note also that it is not clear how to get the current background mode, > either from terminal-parameter or overridden by frame-background-mode, > i.e. the value of frame-background-mode if set to non-nil, else the > value of the background-mode terminal parameter (or whatever method > defined in the future). > > BTW, in both cases, (face-background 'default) gives "unspecified-bg". > Shouldn't the background color reported via the escape sequence in > xterm.el be used to set the background color name? The documentation > for face-background says > > On TTY frames, the returned color name can be "unspecified-bg", > which stands for the unknown default background color of the display > where the frame is displayed. > > but here, the default background color is known from the response to > the escape sequence. > > FYI, the chat for debugging: > > https://chat.mistral.ai/chat/bfb8687b-c60f-4e76-b15e-95951d0d11f3 > > and the context: > > https://github.com/kiwanami/emacs-calfw/issues/189 This seems to be a missing feature: we don't set the default face's background color when xterm is capable of reporting it, and we assume the background mode is 'light' unless changed. Patches to implement these missing features are welcome. Adding Jared in case he has comments or suggestions.
bug-gnu-emacs@HIDDEN:bug#79765; Package emacs.
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From: Vincent Lefevre <vincent@HIDDEN>
To: bug-gnu-emacs@HIDDEN
Subject: 30.1; term/xterm.el does not set background-mode to 'light for
light terminal backgrounds
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With "emacs -Q" in xterm and GNOME Terminal, both with
TERM=3Dxterm-256color:
(terminal-parameter nil 'background-mode)
gives 'dark with a black background, but nil with a white background
instead of 'light as documented: Section 30.5 "Terminal Parameters"
of the Emacs Lisp (elisp) manual says
=E2=80=98background-mode=E2=80=99
The classification of the terminal's background color, either
=E2=80=98light=E2=80=99 or =E2=80=98dark=E2=80=99.
The command
printf '\e]11;?\e\\'
in the terminal gives the correct response:
11;rgb:0000/0000/0000 with a black background;
11;rgb:ffff/ffff/ffff with a white background.
It appears that the background-mode terminal parameter is set by
lisp/term/xterm.el, which contains
(defun xterm-maybe-set-dark-background-mode (redc greenc bluec)
;; Use the heuristic in `frame-set-background-mode' to decide if a
;; frame is dark.
(when (< (+ redc greenc bluec) (* .6 (+ 65535 65535 65535)))
(set-terminal-parameter nil 'background-mode 'dark)
t))
to set 'background-mode to 'dark, but there is nothing to set it
to 'light, and I think that this explains the current behavior.
Note also that it is not clear how to get the current background mode,
either from terminal-parameter or overridden by frame-background-mode,
i.e. the value of frame-background-mode if set to non-nil, else the
value of the background-mode terminal parameter (or whatever method
defined in the future).
BTW, in both cases, (face-background 'default) gives "unspecified-bg".
Shouldn't the background color reported via the escape sequence in
xterm.el be used to set the background color name? The documentation
for face-background says
On TTY frames, the returned color name can be "unspecified-bg",
which stands for the unknown default background color of the display
where the frame is displayed.
but here, the default background color is known from the response to
the escape sequence.
FYI, the chat for debugging:
https://chat.mistral.ai/chat/bfb8687b-c60f-4e76-b15e-95951d0d11f3
and the context:
https://github.com/kiwanami/emacs-calfw/issues/189
In GNU Emacs 30.1 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.24.50,
cairo version 1.18.4) of 2025-10-14, modified by Debian built on sbuild
Windowing system distributor 'The X.Org Foundation', version 11.0.12101018
System Description: Debian GNU/Linux forky/sid
Configured using:
'configure --build x86_64-linux-gnu --prefix=3D/usr
--sharedstatedir=3D/var/lib --libexecdir=3D/usr/libexec
--localstatedir=3D/var/lib --infodir=3D/usr/share/info
--mandir=3D/usr/share/man --with-libsystemd --with-pop=3Dyes
--enable-locallisppath=3D/etc/emacs:/usr/local/share/emacs/30.1/site-lisp:=
/usr/local/share/emacs/site-lisp:/usr/share/emacs/30.1/site-lisp:/usr/share=
/emacs/site-lisp
--with-sound=3Dalsa --without-gconf --with-mailutils --build
x86_64-linux-gnu --prefix=3D/usr --sharedstatedir=3D/var/lib
--libexecdir=3D/usr/libexec --localstatedir=3D/var/lib
--infodir=3D/usr/share/info --mandir=3D/usr/share/man --with-libsystemd
--with-pop=3Dyes
--enable-locallisppath=3D/etc/emacs:/usr/local/share/emacs/30.1/site-lisp:=
/usr/local/share/emacs/site-lisp:/usr/share/emacs/30.1/site-lisp:/usr/share=
/emacs/site-lisp
--with-sound=3Dalsa --without-gconf --with-mailutils --with-cairo
--with-x=3Dyes --with-x-toolkit=3Dgtk3 --with-toolkit-scroll-bars
'CFLAGS=3D-g -O2 -Werror=3Dimplicit-function-declaration
-ffile-prefix-map=3D/build/reproducible-path/emacs-30.1+1=3D.
-fstack-protector-strong -fstack-clash-protection -Wformat
-Werror=3Dformat-security -fcf-protection -Wall' 'CPPFLAGS=3D-Wdate-time
-D_FORTIFY_SOURCE=3D2' LDFLAGS=3D-Wl,-z,relro'
Configured features:
ACL CAIRO DBUS FREETYPE GIF GLIB GMP GNUTLS GPM GSETTINGS HARFBUZZ JPEG
LCMS2 LIBOTF LIBSELINUX 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 $LC_COLLATE: POSIX
value of $LC_CTYPE: C.UTF-8
value of $LC_TIME: en_DK.utf8
value of $LANG: C.UTF-8
locale-coding-system: utf-8-unix
Major mode: Lisp Interaction
Minor modes in effect:
display-time-mode: t
tooltip-mode: t
global-eldoc-mode: t
eldoc-mode: t
show-paren-mode: t
electric-indent-mode: t
mouse-wheel-mode: t
menu-bar-mode: t
file-name-shadow-mode: t
global-font-lock-mode: t
font-lock-mode: t
blink-cursor-mode: t
minibuffer-regexp-mode: t
column-number-mode: t
line-number-mode: t
transient-mark-mode: t
auto-composition-mode: t
auto-encryption-mode: t
auto-compression-mode: t
Load-path shadows:
/usr/share/emacs/site-lisp/llvm-13/llvm-mode hides /usr/share/emacs/site-li=
sp/llvm-14/llvm-mode
/usr/share/emacs/site-lisp/llvm-13/tablegen-mode hides /usr/share/emacs/sit=
e-lisp/llvm-14/tablegen-mode
/usr/share/emacs/site-lisp/llvm-13/emacs hides /usr/share/emacs/site-lisp/l=
lvm-14/emacs
/usr/share/emacs/site-lisp/llvm-13/llvm-mode hides /usr/share/emacs/site-li=
sp/llvm-15/llvm-mode
/usr/share/emacs/site-lisp/llvm-13/tablegen-mode hides /usr/share/emacs/sit=
e-lisp/llvm-15/tablegen-mode
/usr/share/emacs/site-lisp/llvm-13/emacs hides /usr/share/emacs/site-lisp/l=
lvm-15/emacs
/usr/share/emacs/site-lisp/llvm-13/llvm-mode hides /usr/share/emacs/site-li=
sp/llvm-16/llvm-mode
/usr/share/emacs/site-lisp/llvm-13/tablegen-mode hides /usr/share/emacs/sit=
e-lisp/llvm-16/tablegen-mode
/usr/share/emacs/site-lisp/llvm-13/emacs hides /usr/share/emacs/site-lisp/l=
lvm-16/emacs
/usr/share/emacs/site-lisp/llvm-13/llvm-mode hides /usr/share/emacs/site-li=
sp/llvm-17/llvm-mode
/usr/share/emacs/site-lisp/llvm-13/tablegen-mode hides /usr/share/emacs/sit=
e-lisp/llvm-17/tablegen-mode
/usr/share/emacs/site-lisp/llvm-13/emacs hides /usr/share/emacs/site-lisp/l=
lvm-17/emacs
/usr/share/emacs/site-lisp/llvm-13/llvm-mode hides /usr/share/emacs/site-li=
sp/llvm-18/llvm-mode
/usr/share/emacs/site-lisp/llvm-13/tablegen-mode hides /usr/share/emacs/sit=
e-lisp/llvm-18/tablegen-mode
/usr/share/emacs/site-lisp/llvm-13/emacs hides /usr/share/emacs/site-lisp/l=
lvm-18/emacs
/usr/share/emacs/site-lisp/llvm-13/llvm-mode hides /usr/share/emacs/site-li=
sp/llvm-19/llvm-mode
/usr/share/emacs/site-lisp/llvm-13/tablegen-mode hides /usr/share/emacs/sit=
e-lisp/llvm-19/tablegen-mode
/usr/share/emacs/site-lisp/llvm-13/emacs hides /usr/share/emacs/site-lisp/l=
lvm-19/emacs
/usr/share/emacs/site-lisp/elpa/markdown-mode-2.7/markdown-mode-pkg hides /=
usr/share/emacs/site-lisp/elpa-src/markdown-mode-2.7/markdown-mode-pkg
/usr/share/emacs/site-lisp/elpa/markdown-mode-2.7/markdown-mode-autoloads h=
ides /usr/share/emacs/site-lisp/elpa-src/markdown-mode-2.7/markdown-mode-au=
toloads
/usr/share/emacs/site-lisp/elpa/markdown-mode-2.7/markdown-mode hides /usr/=
share/emacs/site-lisp/elpa-src/markdown-mode-2.7/markdown-mode
/usr/share/emacs/site-lisp/elpa/po-mode-0.23.1/po-mode-autoloads hides /usr=
/share/emacs/site-lisp/elpa-src/po-mode-0.23.1/po-mode-autoloads
/usr/share/emacs/site-lisp/elpa/po-mode-0.23.1/po-mode hides /usr/share/ema=
cs/site-lisp/elpa-src/po-mode-0.23.1/po-mode
/usr/share/emacs/site-lisp/elpa/po-mode-0.23.1/po-mode-pkg hides /usr/share=
/emacs/site-lisp/elpa-src/po-mode-0.23.1/po-mode-pkg
/usr/share/emacs/site-lisp/flim/sasl hides /usr/share/emacs/30.1/lisp/net/s=
asl
/usr/share/emacs/site-lisp/latex-cjk-thai/thai-word hides /usr/share/emacs/=
30.1/lisp/language/thai-word
Features:
(shadow sort mail-extr cl-extra help-mode warnings emacsbug message
yank-media puny dired dired-loaddefs rfc822 mml mml-sec epa derived epg
rfc6068 epg-config gnus-util text-property-search time-date mm-decode
mm-bodies mm-encode mail-parse rfc2231 mailabbrev gmm-utils mailheader
sendmail rfc2047 rfc2045 ietf-drums mm-util mail-prsvr mail-utils
cus-start time cc-styles cc-align cc-engine cc-vars cc-defs w3m-load
mmm-auto mmm-vars mmm-utils mmm-compat cus-edit pp cus-load wid-edit
markdown-mode-autoloads po-mode-autoloads package browse-url url
url-proxy url-privacy url-expand url-methods url-history url-cookie
generate-lisp-file url-domsuf url-util mailcap url-handlers url-parse
auth-source cl-seq eieio eieio-core cl-macs icons password-cache json
subr-x map byte-opt gv bytecomp byte-compile url-vars cl-loaddefs cl-lib
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 132490 11543) (symbols 48 11103 0) (strings 32 31378 3001)
(string-bytes 1 1021329) (vectors 16 15904)
(vector-slots 8 449625 72182) (floats 8 49 6) (intervals 56 340 0)
(buffers 992 11))
--=20
Vincent Lefevre <vincent@HIDDEN>:bug-gnu-emacs@HIDDEN.
Full text available.bug-gnu-emacs@HIDDEN:bug#79765; Package emacs.
Full text available.
GNU bug tracking system
Copyright (C) 1999 Darren O. Benham,
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1994-97 Ian Jackson.