GNU bug report logs - #76481
31.0.50; Extreme weirdness with GDK_SCALE=

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Jonathan Corbet <corbet <at> lwn.net>
To: bug-gnu-emacs <at> gnu.org
Subject: 31.0.50; Extreme weirdness with GDK_SCALE=
Date: Fri, 21 Feb 2025 15:11:26 -0700

With emacs built to use GTK, and running under Wayland...  run:

   $ GDK_SCALE= emacs

The result is a number of hallucinogenic effects ranging from emacs just
showing up as a black square on the screen to window-resizing attempts
setting the frame to random sizes unrelated to mouse movements.

Things work much better without GDK_SCALE= and I can happily take that
out (it was put into my scripts years ago for long-forgotten reasons),
but other users may be tripped up by this too.

This happens even with "emacs -q".


In GNU Emacs 31.0.50 (build 1, x86_64-pc-linux-gnu, GTK+ Version
 3.24.43, cairo version 1.18.2) of 2025-02-20 built on trenco
Repository revision: 4411d0de1d5cbf308440982084ad7e15a18efaf2
Repository branch: master
Windowing system distributor 'The X.Org Foundation', version 11.0.12401005
System Description: Fedora Linux 41 (Workstation Edition)

Configured features:
ACL CAIRO DBUS FREETYPE GIF GLIB GMP GNUTLS GPM GSETTINGS HARFBUZZ JPEG
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 XINERAMA XINPUT2 XPM
XRANDR GTK3 ZLIB

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

Major mode: notmuch-hello

Minor modes in effect:
  server-mode: t
  global-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
  minibuffer-regexp-mode: 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:
/home/corbet/.emacs.d/elpa/transient-20210525.1141/transient hides /usr/local/share/emacs/31.0.50/lisp/transient

Features:
(shadow sort flyspell ispell mail-extr emacsbug lisp-mnt cl-extra
help-mode server notmuch notmuch-tree notmuch-jump notmuch-hello
notmuch-show notmuch-print notmuch-crypto notmuch-mua notmuch-message
notmuch-draft notmuch-maildir-fcc notmuch-address notmuch-company
notmuch-parser notmuch-wash diff-mode track-changes easy-mmode coolj
goto-addr icalendar diary-lib diary-loaddefs cal-menu calendar
cal-loaddefs notmuch-tag crm notmuch-lib notmuch-version notmuch-compat
pcase hl-line mm-view mml-smime smime dig delsel cus-edit pp cus-load
gnus-topic gnus-sum shr pixel-fill kinsoku url-file svg dom gnus-group
gnus-undo gnus-start gnus-dbus dbus comp-run comp-common xml gnus-cloud
nnimap nnmail mail-source utf7 nnoo parse-time iso8601 gnus-spec
gnus-int gnus-range message sendmail yank-media dired dired-loaddefs
rfc822 mml mml-sec epa derived epg rfc6068 epg-config mm-decode
mm-bodies mm-encode mail-parse rfc2231 rfc2047 rfc2045 ietf-drums
mailabbrev gmm-utils mailheader gnus-win gnus nnheader gnus-util
time-date mail-utils range mm-util mail-prsvr wid-edit rust-utils
thingatpt rust-mode rx rust-rustfmt rust-playpen rust-compile compile
text-property-search comint ansi-osc ansi-color ring rust-cargo tls
gnutls puny erc format-spec erc-backend erc-networks erc-common
erc-compat compat erc-loaddefs finder-inf info package browse-url xdg
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 dynamic-setting system-font-setting
font-render-setting cairo gtk x-toolkit xinput2 x multi-tty move-toolbar
make-network-process tty-child-frames native-compile emacs)

Memory information:
((conses 16 377895 34873) (symbols 48 25532 0) (strings 32 110328 5426)
 (string-bytes 1 3032008) (vectors 16 35145) (vector-slots 8 450204 28776)
 (floats 8 178 224) (intervals 56 434 26) (buffers 992 13))

Message #8 received at 76481 <at> debbugs.gnu.org (full text, mbox):

From: Po Lu <luangruo <at> yahoo.com>
To: Jonathan Corbet <corbet <at> lwn.net>
Cc: 76481 <at> debbugs.gnu.org
Subject: Re: bug#76481: 31.0.50; Extreme weirdness with GDK_SCALE=
Date: Sat, 22 Feb 2025 09:23:15 +0800

Jonathan Corbet <corbet <at> lwn.net> writes:

> With emacs built to use GTK, and running under Wayland...  run:
>
>    $ GDK_SCALE= emacs
>
> The result is a number of hallucinogenic effects ranging from emacs just
> showing up as a black square on the screen to window-resizing attempts
> setting the frame to random sizes unrelated to mouse movements.
>
> Things work much better without GDK_SCALE= and I can happily take that
> out (it was put into my scripts years ago for long-forgotten reasons),
> but other users may be tripped up by this too.
>
> This happens even with "emacs -q".

Are you building the X11 configuration of Emacs with GTK, or the PGTK
configuration?

At all events, please place a breakpoint on xg_get_scale and ascertain
what it returns.  I suspect an oversigt in GDK, as it appears that Emacs
does not access this environment variable directly.

Message #11 received at 76481 <at> debbugs.gnu.org (full text, mbox):

From: Jonathan Corbet <corbet <at> lwn.net>
To: Po Lu <luangruo <at> yahoo.com>
Cc: 76481 <at> debbugs.gnu.org
Subject: Re: bug#76481: 31.0.50; Extreme weirdness with GDK_SCALE=
Date: Fri, 21 Feb 2025 19:05:18 -0700

Po Lu <luangruo <at> yahoo.com> writes:

> Jonathan Corbet <corbet <at> lwn.net> writes:
>
>> With emacs built to use GTK, and running under Wayland...  run:
>>
>>    $ GDK_SCALE= emacs
>>
>> The result is a number of hallucinogenic effects ranging from emacs just
>> showing up as a black square on the screen to window-resizing attempts
>> setting the frame to random sizes unrelated to mouse movements.
>>
>> Things work much better without GDK_SCALE= and I can happily take that
>> out (it was put into my scripts years ago for long-forgotten reasons),
>> but other users may be tripped up by this too.
>>
>> This happens even with "emacs -q".
>
> Are you building the X11 configuration of Emacs with GTK, or the PGTK
> configuration?

PGTK.

> At all events, please place a breakpoint on xg_get_scale and ascertain
> what it returns.  I suspect an oversigt in GDK, as it appears that Emacs
> does not access this environment variable directly.

I'll try to get to that in the near future - stay tuned.

Thanks,

jon

Message #14 received at 76481 <at> debbugs.gnu.org (full text, mbox):

From: Jonathan Corbet <corbet <at> lwn.net>
To: Po Lu <luangruo <at> yahoo.com>
Cc: 76481 <at> debbugs.gnu.org
Subject: Re: bug#76481: 31.0.50; Extreme weirdness with GDK_SCALE=
Date: Sat, 22 Feb 2025 10:28:26 -0700

Po Lu <luangruo <at> yahoo.com> writes:

> Jonathan Corbet <corbet <at> lwn.net> writes:
>
>> With emacs built to use GTK, and running under Wayland...  run:
>>
>>    $ GDK_SCALE= emacs
>>
>> The result is a number of hallucinogenic effects ranging from emacs just
>> showing up as a black square on the screen to window-resizing attempts
>> setting the frame to random sizes unrelated to mouse movements.
>>
>> Things work much better without GDK_SCALE= and I can happily take that
>> out (it was put into my scripts years ago for long-forgotten reasons),
>> but other users may be tripped up by this too.
>>
>> This happens even with "emacs -q".
>
> Are you building the X11 configuration of Emacs with GTK, or the PGTK
> configuration?
>
> At all events, please place a breakpoint on xg_get_scale and ascertain
> what it returns.  I suspect an oversigt in GDK, as it appears that Emacs
> does not access this environment variable directly.

OK, if I run it normally (without GDK_SCALE=), I get this

First return, called from x_set_scroll_bar_default_width(): 32
 from xg_update_frame_menubar(): 2
 from xg_wm_set_size_hint(): 2
 from xg_frame_set_char_size(): 2

from here on it's always 2

with GDK_SCALE= :

First return, called from x_set_scroll_bar_default_width(): 16
 from xg_update_frame_menubar(): 1
 from xg_wm_set_size_hint(): 1
 from xg_frame_set_char_size(): 1

...and always 1 thereafter.

Hope that helps?

Thanks,

jon

Message #17 received at 76481 <at> debbugs.gnu.org (full text, mbox):

From: Po Lu <luangruo <at> yahoo.com>
To: Jonathan Corbet <corbet <at> lwn.net>
Cc: 76481 <at> debbugs.gnu.org
Subject: Re: bug#76481: 31.0.50; Extreme weirdness with GDK_SCALE=
Date: Sun, 23 Feb 2025 08:56:32 +0800

Jonathan Corbet <corbet <at> lwn.net> writes:

> OK, if I run it normally (without GDK_SCALE=), I get this
>
> First return, called from x_set_scroll_bar_default_width(): 32
>  from xg_update_frame_menubar(): 2
>  from xg_wm_set_size_hint(): 2
>  from xg_frame_set_char_size(): 2
>
> from here on it's always 2
>
> with GDK_SCALE= :
>
> First return, called from x_set_scroll_bar_default_width(): 16
>  from xg_update_frame_menubar(): 1
>  from xg_wm_set_size_hint(): 1
>  from xg_frame_set_char_size(): 1
>
> ...and always 1 thereafter.
>
> Hope that helps?
>
> Thanks,
>
> jon

My recollection is that on Wayland the scale is decided by the
compositor, but apparently GDK continues to report and use the value of
GDK_SCALE in some contexts, if present, which moves the two out of sync.
Or so I suspect.

Message #20 received at 76481 <at> debbugs.gnu.org (full text, mbox):

From: Jonathan Corbet <corbet <at> lwn.net>
To: Po Lu <luangruo <at> yahoo.com>
Cc: 76481 <at> debbugs.gnu.org
Subject: Re: bug#76481: 31.0.50; Extreme weirdness with GDK_SCALE=
Date: Mon, 24 Feb 2025 10:08:54 -0700

Po Lu <luangruo <at> yahoo.com> writes:

> Jonathan Corbet <corbet <at> lwn.net> writes:
>
>> OK, if I run it normally (without GDK_SCALE=), I get this
>>
>> First return, called from x_set_scroll_bar_default_width(): 32
>>  from xg_update_frame_menubar(): 2
>>  from xg_wm_set_size_hint(): 2
>>  from xg_frame_set_char_size(): 2
>>
>> from here on it's always 2
>>
>> with GDK_SCALE= :
>>
>> First return, called from x_set_scroll_bar_default_width(): 16
>>  from xg_update_frame_menubar(): 1
>>  from xg_wm_set_size_hint(): 1
>>  from xg_frame_set_char_size(): 1
>>
>> ...and always 1 thereafter.
>>
>> Hope that helps?
>>
>> Thanks,
>>
>> jon
>
> My recollection is that on Wayland the scale is decided by the
> compositor, but apparently GDK continues to report and use the value of
> GDK_SCALE in some contexts, if present, which moves the two out of sync.
> Or so I suspect.

Something that I think may be related and easier to reproduce... with a
pgtk build:

  $ emacs -q
  <get initial frame, which looks normal>
  C-x 5 b <ret>
  <get *scratch*, probably a tiny frame at most 8 lines high>

It's not 100% reproducible, but happens at least 50% of the time.

FWIW, I also get this in the terminal where I run the editor:

> (emacs:64577): Gtk-CRITICAL **: 10:06:02.686: gtk_distribute_natural_allocation: assertion 'extra_space >= 0' failed

Thanks,

jon

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