1739566 - prefers-color-scheme not working some contents.

Status: RESOLVED INVALID

(Core :: CSS Parsing and Computation, defect)

Description

[alstjr7375]

Attachment: Screenshot_20211105_152857.png

User Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Firefox/91.0

Steps to reproduce:

Load plain text.
https://raw.githubusercontent.com/mozilla/gecko-dev/master/LICENSE

Environment

• Manjro(KDE)
• Error Version: 96.0a1(Nightly)
• Works Version: 94.0(Released Firefox)

Actual results:

A white background appears.

Expected results:

A dark theme should appear.

https://github.com/mozilla/gecko-dev/blob/d2f8488b6a704443a5c5bfc6d2878171b5f0d393/layout/style/res/plaintext.css#L21-L31
(The behavior of unobservable-document() has no problem.)

Comment 1

[Tom S. (please needinfo tschuster)]

Can you share your about:support information here? (Attach a new file)

Comment 2

[alstjr7375]

Attachment: ff94.txt

Of course

firefox94 Info

Comment 3

[alstjr7375]

Attachment: ff96.txt

Firefox 96 info.

The strange thing is that it works well in some pages, such as about:support or setting.

Comment 4

[Emilio Cobos Álvarez [:emilio]]

Can you run pip install --user mozregression and then mozregression --good 94 -a https://raw.githubusercontent.com/mozilla/gecko-dev/master/LICENSE? That should show what broke it on your setup.

Also, does opening the devtools on https://raw.githubusercontent.com/mozilla/gecko-dev/master/LICENSE and calling matchMedia("(prefers-color-scheme: dark)").matches say true?

Thanks so much.

Comment 5

[alstjr7375]

It looks good in mozregression.

---

FF94

• Github contents matchMedia("(prefers-color-scheme: dark)").matches: true

FF96 (Nightly)

• matchMedia("(prefers-color-scheme: dark)").matches: false

It works for internal addresses(about:*, chrome://*) in Firefox, but not external addresses(google.com, addons.mozilla.org).

---

I investigated a little more to find out the situation.
When I create a new profile, it seems to work normally.
There seems to be something conflicting with the profile.

Comment 6

[alstjr7375]

Thanks for your kind response!!

Would you like profile information?
If you need, I will attach it.

Comment 7

[Emilio Cobos Álvarez [:emilio]]

Yeah would be interesting to know if you have any ui.* pref customized, or layout.css.prefers-color-scheme.content-override

Comment 8

[alstjr7375]

The file was large so I used Google Drive.
https://drive.google.com/file/d/1j2mzeZY2mmTXE5B1_NT1d8NN_SbLkS2O/view?usp=sharing

Comment 9

[Emilio Cobos Álvarez [:emilio]]

Thanks. That is because of privacy.resistFingerprinting=true, which you had set.

Comment 10

[alstjr7375]

Thank you very much! 👍👍
I never thought it was about privacy setting.