Bug#1136725: gnome-control-center: Display settings fail to apply mirror mode for 16:10 laptop panel and 16:9 external monitor, while Mutter D-Bus succeeds
Giuliano Aniello
giuliano.aniello at proton.me
Fri May 15 10:58:35 BST 2026
Package: gnome-control-center
Version: 1:48.4-1~deb13u1
Severity: normal
Tags: upstream
Dear Maintainer,
GNOME Settings does not reliably apply mirror/duplicate mode for my
internal laptop panel and external monitor, while Mutter's D-Bus API can
apply the same configuration successfully.
System:
- Debian GNU/Linux 13.4 (trixie)
- Package: gnome-control-center 1:48.4-1~deb13u1
- GNOME Shell: 48.7-0+deb13u2
- Mutter common files: 48.7-0+deb13u1
- Session: GNOME on Wayland
- Kernel: 6.12.86+deb13-amd64
- Mutter experimental-features:
['scale-monitor-framebuffer', 'xwayland-native-scaling']
Displays:
- Internal display: eDP-1, CSO 0x1413, native/preferred
1920x1200 at 60.001, 16:10
- External display: DP-3, Philips PHL 271V8, preferred
1920x1080 at 60.000, 16:9
Steps to reproduce:
1. Log in to a GNOME Wayland session.
2. Connect the external Philips 1920x1080 monitor.
3. Open GNOME Settings > Displays.
4. Try to enable mirror/duplicate mode between the internal panel and
the external monitor.
5. Apply the configuration.
Expected result:
GNOME Settings should apply mirror mode using a common mode supported by
both outputs, for example 1920x1080.
Actual result:
GNOME Settings does not successfully apply the mirror configuration for
me. No useful error is shown in the UI.
Important detail:
Applying the same mirror configuration directly through Mutter's
DisplayConfig D-Bus API succeeds. The working configuration is one
logical monitor containing both outputs:
- eDP-1: 1920x1080 at 59.934
- DP-3: 1920x1080 at 60.000
- scale: 1.0
- primary: yes
The command used was:
gdbus call --session \
--dest org.gnome.Mutter.DisplayConfig \
--object-path /org/gnome/Mutter/DisplayConfig \
--method org.gnome.Mutter.DisplayConfig.ApplyMonitorsConfig \
9 2 \
"[(0, 0, 1.0, uint32 0, true, [('eDP-1', '1920x1080 at 59.934', {}), ('DP-3', '1920x1080 at 60.000', {})])]" \
"{'layout-mode': <uint32 1>}"
After this, GetCurrentState reports a single logical monitor with both
eDP-1 and DP-3 attached, confirming that mirroring is active:
[(0, 0, 1.0, uint32 0, true,
[('eDP-1', 'CSO', '0x1413', '0x00000000'),
('DP-3', 'PHL', 'PHL 271V8', '0x00007580')],
{})]
Also, ~/.config/monitors.xml is regenerated correctly and contains the
mirrored configuration. The file is writable by my user and is not
immutable:
- permissions: -rw-rw-r--
- owner/group: jul:jul
- lsattr: --------------e-------
This suggests that Mutter can apply the monitor configuration, but the
GNOME Settings display panel fails or mishandles this case, possibly
because the two displays have different native aspect ratios and
fractional scaling support is enabled.
No relevant mutter, gnome-control-center, displayconfig, monitors.xml, or
dconf error was found in the recent user journal while checking this.
-- System Information:
Debian Release: 13.4
Architecture: amd64
Kernel: Linux 6.12.86+deb13-amd64
GNOME Shell: 48.7
GNOME Control Center: 48.4
Session type: wayland
-- System Information:
Debian Release: 13.4
APT prefers stable-updates
APT policy: (500, 'stable-updates'), (500, 'stable-security'), (500, 'stable')
Architecture: amd64 (x86_64)
Kernel: Linux 6.12.86+deb13-amd64 (SMP w/14 CPU threads; PREEMPT)
Locale: LANG=it_IT.UTF-8, LC_CTYPE=C.UTF-8 (charmap=UTF-8) (ignored: LC_ALL set to C.UTF-8), LANGUAGE not set
Shell: /bin/sh linked to /usr/bin/dash
Init: systemd (via /run/systemd/system)
LSM: AppArmor: enabled
Versions of packages gnome-control-center depends on:
ii accountsservice 23.13.9-7
ii colord 1.4.7-3
ii desktop-base 13.0.4
ii desktop-file-utils 0.28-1
ii gnome-control-center-data 1:48.4-1~deb13u1
ii gnome-desktop3-data 44.3-3
ii gnome-online-accounts 3.54.5-1~deb13u1
ii gnome-settings-daemon 48.1-1
ii gsettings-desktop-schemas 48.0-1
ii heif-gdk-pixbuf 1.19.8-1
ii heif-thumbnailer 1.19.8-1
ii libaccountsservice0 23.13.9-7
ii libadwaita-1-0 1.7.6-1~deb13u1
ii libc6 2.41-12+deb13u2
ii libcairo2 1.18.4-1+b1
ii libcolord-gtk4-1t64 0.3.1-1+b1
ii libcolord2 1.4.7-3
ii libcups2t64 2.4.10-3+deb13u2
ii libepoxy0 1.5.10-2
ii libfontconfig1 2.15.0-2.3
ii libgcr-4-4 4.4.0.1-3
ii libgdk-pixbuf-2.0-0 2.42.12+dfsg-4+deb13u1
ii libglib2.0-0t64 2.84.4-3~deb13u2
ii libgnome-bg-4-2t64 44.3-3
ii libgnome-bluetooth-ui-3.0-13 47.1-1
ii libgnome-desktop-4-2t64 44.3-3
ii libgnome-rr-4-2t64 44.3-3
ii libgnutls30t64 3.8.9-3+deb13u2
ii libgoa-1.0-0b 3.54.5-1~deb13u1
ii libgoa-backend-1.0-2 3.54.5-1~deb13u1
ii libgraphene-1.0-0 1.10.8-5
ii libgsound0t64 1.0.3-3.2+b4
ii libgtk-4-1 4.18.6+ds-2
ii libgtk-4-media-gstreamer 4.18.6+ds-2
ii libgtop-2.0-11 2.41.3-1+b2
ii libgudev-1.0-0 238-6
ii libibus-1.0-5 1.5.32-2
ii libjson-glib-1.0-0 1.10.6+ds-2
ii libjxl-gdk-pixbuf 0.11.1-4
ii libkrb5-3 1.21.3-5
ii libmalcontent-0-0 0.13.0-2+deb13u1
ii libmm-glib0 1.24.0-1+deb13u1
ii libnm0 1.52.1-1
ii libnma-gtk4-0 1.10.6-5
ii libpango-1.0-0 1.56.3-1
ii libpolkit-gobject-1-0 126-2
ii libpulse-mainloop-glib0 17.0+dfsg1-2+b1
ii libpulse0 17.0+dfsg1-2+b1
ii libpwquality1 1.4.5-5
ii libsecret-1-0 0.21.7-1
ii libsmbclient0 2:4.22.8+dfsg-0+deb13u1
ii libsoup-3.0-0 3.6.5-3
ii libudisks2-0 2.10.1-12.1+deb13u1
ii libupower-glib3 1.90.9-1
ii libwacom9 2.14.0-1
ii libwayland-client0 1.23.1-3
ii libx11-6 2:1.8.12-1
ii libxi6 2:1.8.2-1
ii libxml2 2.12.7+dfsg+really2.9.14-2.1+deb13u2
ii mutter-common 48.7-0+deb13u1
ii tecla 48.0.2-1
ii webp-pixbuf-loader 0.2.7-1+b1
Versions of packages gnome-control-center recommends:
ii cracklib-runtime 2.9.6-5.2+b1
ii cups-pk-helper 0.2.6-2.1
ii fwupd 2.0.8-3
ii gnome-bluetooth-sendto 47.1-1
ii gnome-remote-desktop 48.1-4
ii gnome-user-docs 48.2-1
ii gnome-user-share 48.0-1
ii iso-codes 4.18.0-1
ii libcanberra-pulse 0.30-18
ii libnss-myhostname 257.9-1~deb13u1
ii libspa-0.2-bluetooth 1.4.2-1
ii malcontent-gui 0.13.0-2+deb13u1
ii mobile-broadband-provider-info 20250613-2
ii nm-connection-editor 1.36.0-3+b1
ii polkitd 126-2
ii power-profiles-daemon 0.30-1.1
ii realmd 0.17.1-3+b2
ii rygel 0.44.2-1
ii rygel-tracker 0.44.2-1
ii system-config-printer-common 1.5.18-4
Versions of packages gnome-control-center suggests:
ii gnome-software 48.3-2
ii gstreamer1.0-plugins-good 1.26.2-1
ii x11-xserver-utils 7.7+11
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