Element picker is light themed when uBO theme is set to auto in Firefox Nightly

[bbhtt]

Prerequisites

• I verified that this is not a filter issue (MUST be reported at filter issue tracker)
• This is not a support issue or a question
• I performed a cursory search of the issue tracker to avoid opening a duplicate issue
• The issue is not present after wholly disabling uBlock Origin ("uBO") in the browser
• I checked the documentation to understand that the issue I report is not a normal behavior

I tried to reproduce the issue when...

• uBO is the only extension
• uBO with default lists/settings
• using a new, unmodified browser profile

Description

GNOME 42.4 using system dark mode (Freedesktop colour scheme preference ie. Dark is set in Gnome control center>Appearance>Style), Firefox theme set to System - Auto, uBo theme set to auto.

Open the element picker in any page, it is light themed but uBO itself is dark themed (the settings page and the extension popup).

A specific URL where the issue occurs

https://hg.mozilla.org

Steps to Reproduce

1. Open the element picker in any page

Expected behavior

It should be dark themed

Actual behavior

See that it is light themed

uBlock Origin version

1.44.0

Browser name and version

Firefox Nightly 106.0a1 (2022-09-01) (64-bit)

Operating System and version

Archlinux

[bbhtt]

I bisected this down to

$ mozregression --good 2022-08-10 --bad 2022-08-25

27:02.53 INFO: No more integration revisions, bisection finished.
27:02.53 INFO: Last good revision: 7c1e795e3c0750d5dcd99dab73be28e871c38979
27:02.53 INFO: First bad revision: 495ffb27c683fe2219b559708d3eb415847faa10
27:02.53 INFO: Pushlog:
https://hg.mozilla.org/integration/autoland/pushloghtml?fromchange=7c1e795e3c0750d5dcd99dab73be28e871c38979&tochange=495ffb27c683fe2219b559708d3eb415847faa10

which means https://bugzilla.mozilla.org/show_bug.cgi?id=1782596 is responsible. I think it is the same issue as this one reported as a regression from the previous one https://bugzilla.mozilla.org/show_bug.cgi?id=1787127

Please let me know if this is a separate issue, I can open a bug in BMO.

Thanks!

[gorhill]

It works fine with Firefox 104.0.1, hence it appears to be a regression in Nightly.

[bbhtt]

It works fine with Firefox 104.0.1, hence it appears to be a regression in Nightly.

Yes this happens only in Nightly at the moment.

[krystian3w]

Works fine too in 105.0b6.

[bbhtt]

I think it is the same issue as this one reported as a regression from the previous one https://bugzilla.mozilla.org/show_bug.cgi?id=1787127

Wasn't fixed on today's nightly, which seems to include it as far as I can tell. So I've opened https://bugzilla.mozilla.org/show_bug.cgi?id=1789338

[emilio]

Yeah, this seems kind of an unfortunate side-effect of the fix for #1408. The relevant <iframe> that uBlock injects has color-scheme: light, so as per w3c/csswg-drafts#7493, it now matches prefers-color-scheme: light.

Removing that, and just having the inherited color-scheme go through, would just work, and allow the iframe to remain transparent. But in Chromium which hasn't implemented this yet it'd regress that issue... So it's a bit tricky...

[gorhill]

But in Chromium which hasn't implemented this yet it'd regress that issue... So it's a bit tricky...

I can inject color-scheme: light conditionally only when browser is not Firefox version 106+. @emilio This works?

[uBlock-user]

with github dark theme after gorhill/uBlock@707609d --

[emilio]

@gorhill that doesn't quite work, I can write a patch that works everywhere. In fact I thought I replied to your comment and sent it already, but I must've dreamed it, sorry :-(

[emilio]

@gorhill gorhill/uBlock#3872

[rishiraj88]

Great!