Closed Bug 1978639 Opened 4 months ago Closed 4 months ago

Dark Theme not working with 141.0 on Linux Mint

Categories

(Core :: Widget: Gtk, defect)

Product:
Core
Component:
Widget: Gtk
Version:
Firefox 141
Type:
defect

Tracking

()

Status:
RESOLVED INVALID
Tracking Flags:
Tracking Status
firefox-esr115 --- unaffected
firefox-esr128 --- unaffected
firefox-esr140 --- unaffected
firefox141 --- wontfix
firefox142 --- wontfix
firefox143 --- wontfix

People

(Reporter: sarcyleo, Unassigned)

References

(Regression)

Details

(Keywords: regression)

Attachments

(2 files)

look and feel log
94.57 KB, text/plain
Details
system info
10.66 KB, text/plain
Details

User Agent: Mozilla/5.0 (X11; Linux x86_64; rv:141.0) Gecko/20100101 Firefox/141.0

Steps to reproduce:

I'm using Linux Mint 22.1 and Cinnamon 6.4.8

I just open firefox with my OS theme set to dark mode

Actual results:

Firefox (sync with system theme) open with light mode, and even if i set dark mode in firefox setting, I have the top bar that remains in light mode

Expected results:

It should be entirely dark (as in previous version)

perhaps you could use https://mozilla.github.io/mozregression/ to determine when this changed.

Flags: needinfo?(sarcyleo)

The Bugbug bot thinks this bug should belong to the 'Core::Widget: Gtk' component, and is moving the bug to that component. Please correct in case you think the bot is wrong.

Component: Untriaged → Widget: Gtk
Product: Firefox → Core

It was dark with "mozilla-central build: 2025-05-28" and it became light with "mozilla-central build: 2025-05-29".

Flags: needinfo?(sarcyleo)

Having the same issue. After Mint upgraded Firefox, the system dark theme is no longer honored.

The active theme is still "System theme — auto" but it's falsely detected as light instead of dark.

The version upgrade was from 140.0.4+linuxmint1+xia to 141.0+linuxmint1+xia

Also ran mozregression, commit message is very relevant:

2025-07-22T21:49:32.462000: DEBUG : Found commit message:
Bug 1968664 - Always honor dbus color-scheme preference if present. r=stransky

Right now, we're making 0 / default fall back effectively to
`gtk-application-prefers-dark-theme`.

This is an issue because some tools like kde-gtk-config and such do set
that value, and make firefox look as if it's not respecting the D-BUS
setting.

If we get the dbus preference, use it. This matches what libraries like
libadwaita do.

Differential Revision: https://phabricator.services.mozilla.com/D251327


2025-07-22T21:49:32.462000: DEBUG : Did not find a branch, checking all integration branches
2025-07-22T21:49:32.462000: INFO : The bisection is done.
2025-07-22T21:49:32.462000: INFO : Stopped

I think this is invalid. That means that your d-bus settings portal is not communicating the dark mode preference. I'm not sure which portal does mint use, or how is it hooked up to the settings.

This appears to be a Cinnamon/Mint issue. Changing the Cinnamon theme to light and back to dark causes Firefox to switch to dark theme. Rebooting brings it back to light theme.

I'm sorry Emilio, if you made any changes to this bug other than commenting I accidentally undid them.

Either way, I'd like to report this issue to Cinnamon (or perhaps even try fixing it). Can you tell me what exactly gets changed when switching to dark mode to tell Firefox to also switch to dark mode? I don't know the background for this.

Ok, so I can reproduce locally. It seems in the Cinnamon settings there is a "Dark mode" option which actually exposes three values (let applications decide, prefer dark mode, prefer light mode).

My patch made Firefox interpret the first on as "light". The reason is that in other environments like GNOME or KDE they will just expose, effectively, the first two options. But given Cinnamon exposes the three "properly", I should probably restore the pre-existing behavior on cinnamon.

Can you confirm that Firefox honors the "Prefer dark mode" setting properly, and this regression only happens with "Let applications decide"?

I assume you mean "Mixed", "Dark" and "Light" options as they appear in the Themes settings. It does work as you described when changing theme at runtime, but please try rebooting after selecting "Dark".

After rebooting, Firefox will be light regardless of selected setting.

Oh, actually you don't need to reboot or even log out. Firefox at launch ignores the Dark option, but honors it if it's changed while Firefox is running. Can you reproduce this?

I see. I had the "Advanced" settings which has a dropdown (I for some reason can't make a choice in the "simplified" settings because it says my style is "custom", probably because I don't usually use cinnamon).

(In reply to NeatNit from comment #11)

Can you reproduce this?

I can't at firefox launch at least. Will try reboot now.

I'm on Cinnamon 6.4.10. If you can launch firefox with MOZ_LOG=LookAndFeel:5 in the environment and attach the output here that might be another avenue for investigation.

I see. I just tried that setting in Advanced setting and still see the same behavior: closing and opening Firefox will always be light mode.

Attached file look and feel log —
(In reply to Emilio Cobos Álvarez (:emilio) from comment #13) > I'm on Cinnamon 6.4.10. If you can launch firefox with `MOZ_LOG=LookAndFeel:5` in the environment and attach the output here that might be another avenue for investigation. Did this. After launching, I switched system theme to Light and then Dark (using simplified settings). ``` ```

Ok, it seems it might have been fixed upstream? Which version of cinnamon are you on?

neatnit@NeatStation:~$ cinnamon --version
Cinnamon 6.4.8

Ok, it seems you somehow have two portals running or something along those lines?

[Parent 16164: Main Thread]: D/LookAndFeel dbus settings query result: ({'org.freedesktop.appearance': {'contrast': <uint32 0>, 'color-scheme': <uint32 1>}, 'org.freedesktop.appearance': {'color-scheme': <uint32 0>}},)

See how there are two color-scheme values ("dark" and "no-preference")

Summary: Dark Theme not working with 141.0 → Dark Theme not working with 141.0 on Linux Mint

Well, that's a few steps beyond my knowledge. I really don't know what that means other than it sounds wrong and it's probably (but not definitely) not my fault!

Would be happy to learn more and debug more but will need some guidance.

What shows up if you do ps -ax | grep desktop-portal on a terminal?

neatnit@NeatStation:~$ ps -ax | grep desktop-portal
   2391 ?        Ssl    0:00 /usr/libexec/xdg-desktop-portal
   2410 ?        Ssl    0:00 /usr/libexec/xdg-desktop-portal-xapp
  10786 ?        Ssl    0:00 /usr/libexec/xdg-desktop-portal-gtk
  21357 pts/0    S+     0:00 grep --color=auto desktop-portal
neatnit@NeatStation:~$

Which distro are you on? IIUC the main portal should be xapp, that's the cinnamon one. It seems the gtk portal is what's causing the conflict in this case, but I'm not sure how that one is configured or what not.

Flags: needinfo?(emilio)
Attached file system info —
Linux Mint 22.1 Cinnamon.

Ok, I think I found how to repro this. Can you confirm that:

$ dconf read /org/gnome/desktop/interface/color-scheme

Shows default (or prefer-light, but most likely default).

And that:

$ dconf write /org/gnome/desktop/interface/color-scheme "'prefer-dark'"

(note the odd quotes) fixes the issue for you?

If so... It does seem like a problem external to Firefox. I'm guessing cinnamon should also set that dconf setting?

Flags: needinfo?(NeatNit)

It's not set at all:

neatnit@NeatStation:~$ dconf read /org/gnome/desktop/interface/color-scheme
neatnit@NeatStation:~$ dconf watch /
/org/x/apps/portal/color-scheme
  'prefer-light'

/org/cinnamon/desktop/interface/gtk-theme
  'Mint-Y-Orange'
/org/cinnamon/theme/name
  'Mint-Y-Orange'

/org/gnome/desktop/interface/gtk-theme
  'Mint-Y-Orange'

/org/x/apps/portal/color-scheme
  'prefer-dark'

/org/cinnamon/desktop/interface/gtk-theme
  'Mint-Y-Dark-Orange'
/org/cinnamon/theme/name
  'Mint-Y-Dark-Orange'

/org/gnome/desktop/interface/gtk-theme
  'Mint-Y-Dark-Orange'

^C

(switched to light and back to dark while watching)

Flags: needinfo?(NeatNit)

After I ran the dconf write command you gave me, Firefox launches in dark mode, even if the Cinnamon theme is set to Light.

So should Cinnamon set /org/gnome/desktop/interface/color-scheme which it currently doesn't? Or should Firefox be looking at /org/x/apps/portal/color-scheme?

Firefox is doing neither. It's doing effectively:

$ qdbus6 --literal org.freedesktop.portal.Desktop /org/freedesktop/portal/desktop org.freedesktop.portal.Settings.ReadAll 'org.freedesktop.appearance'

The issue is that, for you, was returning two values, rather than one.

Ok, did some digging since I still can't repro.

Fairly sure now the issue is your distro is missing https://github.com/flatpak/xdg-desktop-portal/pull/1538 and related changes (not sure what needs to happen where to get all those fixes into linux mint).

So basically before that change (https://github.com/flatpak/xdg-desktop-portal/commit/49ee1c0d535608f6a5d0a47a1cd510958dc5e34f in particular) you could get different (conflicting) settings from two different portal implementations.

It might be that cinnamon wants to set the /org/gnome/desktop/interface/color-scheme regardless tho, since that'd trivially "fix" this issue?

But fairly sure at this point it's not a Firefox bug.

Status: UNCONFIRMED → RESOLVED
Closed: 4 months ago
Resolution: --- → INVALID
Duplicate of this bug: 1978698
Duplicate of this bug: 1979520
Duplicate of this bug: 1979895
Duplicate of this bug: 1978868
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