Bug 1716134

Summary:	Under KDE firefox CCS media query prefers-color-scheme does not support dark mode
Product:	[Fedora] Fedora	Reporter:	Barry Scott <barry>
Component:	firefox	Assignee:	Gecko Maintainer <gecko-bugs-nobody>
Status:	CLOSED NOTABUG	QA Contact:	Fedora Extras Quality Assurance <extras-qa>
Severity:	unspecified	Docs Contact:
Priority:	unspecified
Version:	29	CC:	0xalen+redhat, anto.trande, gecko-bugs-nobody, jgrulich, jhorak, john.j5live, kde-sig, kengert, me, pjasicek, rdieter, rhughes, rstrode, sandmann, stransky, than
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Hardware:	x86_64
OS:	Linux
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Last Closed:	2019-07-03 07:56:38 UTC	Type:	Bug
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oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
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Description Barry Scott 2019-06-02 07:55:15 UTC

Description of problem:

Under KDE firefox CCS media query prefers-color-scheme does not support dark mode.

Version-Release number of selected component (if applicable):

firefox 67.

How reproducible:

Steps to Reproduce:
1. login to KDE dektop
2. System Settings/Workspace Theme/Look and Feel - choose Breeze Dark
3. Start Firefiox
4. Browse to https://developer.mozilla.org/en-US/docs/Web/CSS/@media/prefers-color-scheme
5. Browse to http://www.barrys-emacs.org/

Actual results:

For mozilla page: notice that in "Results", "Day (changes in dark scheme)" is show light
For barrys-emacs page: page is shown in the light design

Expected results:

For mozilla page: notice that in "Results", "Day (changes in dark scheme)" is show dark
For barrys-emacs page: page is shown in the dark design

Additional info:

Firefox 67 dark mode work for Gnome and macOS

Comment 1 Rex Dieter 2019-06-02 14:48:22 UTC

Triaging to Firefox

Comment 2 Martin Stransky 2019-06-03 07:23:44 UTC

That depends on your actual theme and window text/background color. What if you set Breeze Dark in Gnome, does it work? Thanks.

Comment 3 Barry Scott 2019-06-05 18:17:37 UTC

I do not have gnome installed anywhere to try or know anyone that uses Gnome.

Can you try the Breeze Dark in Gnome yourself?

I assume you are thinking that its the theme that has the bug in it?

Comment 4 Martin Stransky 2019-06-06 08:05:56 UTC

(In reply to Barry Scott from comment #3)
> I do not have gnome installed anywhere to try or know anyone that uses Gnome.
> 
> Can you try the Breeze Dark in Gnome yourself?

As I have hundreds of Firefox bug to fix to I don't put effort to bugs which don't affect large user base and/or reporter is not willing to put an effort into it. The latter tells me that the bug is not important enough for you.

Comment 5 Barry Scott 2019-06-06 17:50:35 UTC

I have no desire to increase your work load,
was baffled by the request.

I looked into what the Breeze Dark theme is.
If I understand correctly its from the plasma-breeze src.rpm
and it KDE specific only (has C++ code in it, not config files).

Therefore its not possible to test with gnome.

I think this bug should be directed towards the KDE folks not firefox.

My guess is that the query that firefox does to set CSS media query prefers-color-scheme
is not working in the KDE environment.

Hope this is helpful.

Comment 6 Rex Dieter 2019-06-06 17:54:34 UTC

I see no evidence this is nothing but firefox-specific behavior, and not a kde bug.  In particular, how is kde/plasma expected to be able to influence firefox behavior?

Comment 7 Barry Scott 2019-06-06 20:04:56 UTC

I have read enought firefix code to know where the decision is made.
I'll report back my finding tomorrow which I get gdb to find out
what is happening at runtime.

Comment 8 Barry Scott 2019-07-03 07:56:38 UTC

Copied from my bug report against Firefox on this matter.

Firefox does need a GTK3 theme. I used the Mojave-dark from the theme store and then Firefox runs in dark mode.

This can be done from the Plasma System-settings by filtering on GTK. That brings up an Application appearance panel
which allows the GTK theme to be configured.

Curiously googling did not bring up any pointers to this mechanism.

Thank you for the help in tracking this down.

I will now close this bug as its resolved.