[css-color-adjust-1] Forced colors mode usage beyond high contrast mode

[beverloo]

https://www.w3.org/TR/css-color-adjust-1/#forced-colors-mode
https://www.w3.org/TR/mediaqueries-5/#forced-colors

[css-mediaqueries-5] defines a new forced-colors media query, that can be set to active when "forced colors mode" is active. This is defined as:

Forced colors mode is an accessibility feature intended to increase the readability of text through color contrast. [...] Users can also customize their own themes, for example to provide low contrast or hue contrast.

Chrome has an experimental feature (available in chrome://flags) to apply a generated Dark Mode to Web Contents that don't provide one themselves. It strikes me that allowing developers to detect this as follows would be very appropriate:

@media (prefers-color-scheme: dark) and (forced-colors: active) {}

I'd like to ask whether it would be appropriate to scope up this definition?

[lilles]

According to the css-color-adjust spec, forced-colors is a different thing than color-scheme override.

One possibility is to introduce a new media feature for this where the feature matches the color-scheme override:

@media (color-scheme-override: dark) {}
@media (color-scheme-override: light) {}
@media (color-scheme-override: none) {}

[lilles]

If fingerprinting is an issue, the color-scheme override is detectable today per spec since system colors are affected by the used value of color-scheme and color-scheme override will affect the used color-scheme in the case where the computed color-scheme does not contain the override color-scheme.

[css-meeting-bot]

The CSS Working Group just discussed [css-color-adjust-1] Forced colors mode usage beyond high contrast mode.

The full IRC log of that discussion

<dael> Topic: [css-color-adjust-1] Forced colors mode usage beyond high contrast mode
<dael> github: https://github.com//issues/6664
<dael> Rossen_: Tagged by rune
<dael> Rossen_: Can anyone take this?
<dael> TabAtkins: fantasai and I can
<dael> TabAtkins: Question is how to reflect UA feature that does forced dark mode. Being tested on Android, I believe iOS has it
<smfr> only forced dark mode in apple mail, not in the browser
<dael> TabAtkins: Suggestion is reflect as a forced colors mode. Would imply we're doing things forced colors does
<dael> TabAtkins: Assuming auto-darkening does match up enough I think that's fine and we reflect that in prefers-color-scheme. Acts like author chose a11y feature to set colors to dark
<dael> TabAtkins: Seems straight forward. Doesn't give authors more things to react to. I suggest we accept Beverly's suggestion
<Rossen_> q?
<dael> Rossen_: Feedback?
<alisonmaher> q+
<dael> smfr: Not sure if auto-darkening and forced colors are same. There's a bunch we resolved on for forced colors that's a lot difference
<Rossen_> ack alisonmaher
<dael> alisonmaher: Haven't looked too much, but I don't think forced dark is same. I think it's paint time. Don't use system colors to force darkening. I don't hitnk impl would match as spec for forced colors
<dael> Rossen_: You're saying darkening is paint?
<dael> alisonmaher: Yes. haven't looked that much
<dael> smfr: That's true of what Apple did in mail
<dael> Rossen_: That's a pretty major difference in behavior. Not sure harmonizing the two makes sense
<alisonmaher> q-
<dael> TabAtkins: Enough difference that authors should react differently? Not sure. If similar enough people can act the same way and for auto-darken should change colors it's fine. If they should do other changes should use another MQ
<dael> Rossen_: Would adjust-color override apply to auto-darkening?
<dael> TabAtkins: I would assume it would
<dlibby> q+
<Rossen_> ack dlibby
<dael> dlibby: Regarding difference between featurs a lot of authors will writed forced-color MQ and use system colors. With forced dark mode being at paint time it could lead to some inconsistencies. Seems hard to map the two concepts directly
<fantasai> +1 to not linking this with forced-colors mode
<dael> Rossen_: Feedback I'm hearing is that even though conceptually there are similarities it doesn't necessarily mean it will be gray-dark or green-dark or whatever in order to match the paint time effects
<dael> Rossen_: I think we should take it back to the issue and do more work there
<dael> Rossen_: Sound reasonable?
<dael> TabAtkins: Yep