1789214 - prefers-color-scheme is not updated according to the selected high contrast theme

Status: VERIFIED FIXED

(Core :: CSS Parsing and Computation, defect)

Description

[Simon Lenz]

Attachment: scrot_2022-09-05_11-14-07_screenshot.png

Steps to reproduce:

1. Enable windows High-Contrast mode with the theme "High Contrast Black"
2. Firefox's appearance setting "System Theme"
3. Look at https://codepen.io/simondl/pen/oNdgpdE in Firefox

Notes:

• On Chromium-based browsers, I get the expected result
• The expected behaviour is described in:
  • https://developer.mozilla.org/en-US/docs/Web/CSS/@media/forced-colors#active and
  • https://blogs.windows.com/msedgedev/2020/09/17/styling-for-windows-high-contrast-with-new-standards-for-forced-colors/#file-forced-colors-2-css-L1

Actual results:

Div (1) spans the whole width.
Div (2) is narrow.
Div (3) spans the whole width.

Expected results:

Div (1) is narrow.
Div (2) is narrow.
Div (3) is narrow.

Comment 1

[BugBot [:suhaib / :marco/ :calixte]]

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

Comment 2

[Rares Doghi, Desktop QA]

I was able to reproduce this issue in all versions of Firefox using the https://codepen.io/simondl/pen/oNdgpdE test case.

Comment 3

[Mike Conley (:mconley) (:⚙️)]

Attachment: Test case

Here's a test case that tries to invert a white SVG icon to be black if we determine that the background is light.

Comment 4

[Emilio Cobos Álvarez (:emilio)]

Attachment: Bug 1789214 - In Windows HCM, derive system color-scheme from the HCM theme background. r=morgan,#win-reviewers

We might want to do this more generally at the PreferencesSheet level
all the times we're forcing colors, but this should be uncontroversial
and fix the default behavior.

Comment 5

[Emilio Cobos Álvarez (:emilio)]

Attachment: Bug 1789214 - When forcing colors without a color-scheme, compute prefers-color-scheme based on them. r=morgan,#style,#layout

This requires moving some code around to PreferenceSheet, but that makes
stuff actually a bit simpler.

Need to add a test for this.

Depends on D192574

Comment 6

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/c25f6d823433
In Windows HCM, derive system color-scheme from the HCM theme background. r=win-reviewers,mhowell
https://hg.mozilla.org/integration/autoland/rev/bdfe284b7ab1
When forcing colors without a color-scheme, compute prefers-color-scheme based on them. r=morgan
https://hg.mozilla.org/integration/autoland/rev/5f1ebbf34671
apply code formatting via Lando

Comment 7

[Cristian Tuns]

https://hg.mozilla.org/mozilla-central/rev/c25f6d823433
https://hg.mozilla.org/mozilla-central/rev/bdfe284b7ab1
https://hg.mozilla.org/mozilla-central/rev/5f1ebbf34671

Comment 8

[Rares Doghi, Desktop QA]

Verified as fixed in our latest Nightly build 121.0a1 (2023-11-07).

Comment 9

[BugBot [:suhaib / :marco/ :calixte]]

The patch landed in nightly and beta is affected.
:emilio, is this bug important enough to require an uplift?

• If yes, please nominate the patch for beta approval.
• If no, please set status-firefox120 to wontfix.

For more information, please visit BugBot documentation.

Comment 10

[Emilio Cobos Álvarez (:emilio)]

Let's let this ride the trains.

Comment 11

[Rares Doghi, Desktop QA]

Updating the main status flag for this issue.