Re: [csswg-drafts] [css-color-adjust-1] background-color in forced color modes needs more than a simple unset (#4175)

The CSS Working Group just discussed `[css-color-adjust-1] background-color in forced color modes needs more than a simple unset`, and agreed to the following:

* `RESOLVED: Select Option B [Based on its resulting computed color value, the [computed|used] background-color of an element is forced by matching all channels other than alpha to the appropriate forced background color; which should be the corresponding system background color if color is a system color, and Canvas otherwise.]`
* `RESOLVED: publish update WD of css-color-adjust-1`

<details><summary>The full IRC log of that discussion</summary>
&lt;dael> Topic: [css-color-adjust-1] background-color in forced color modes needs more than a simple unset<br>
&lt;dael> github: https://github.com/w3c/csswg-drafts/issues/4175#issuecomment-603965581<br>
&lt;dael> spec link: https://drafts.csswg.org/css-color-adjust-1/#forced-colors-properties<br>
&lt;dael> astearns: fantasai put 2 options into the draft<br>
&lt;dael> astearns: She asked us to choose between option A and B. Opinions?<br>
&lt;dael> AmeliaBR: I realized looking at...one thing requested was examples so I did just post a reply with an example.<br>
&lt;astearns> https://codepen.io/AmeliaBR/pen/dyoLMGd<br>
&lt;dael> AmeliaBR: There are screenshots in the issue of what this looks like in a couple high contrast modes.<br>
&lt;dael> AmeliaBR: Including ones that look broken currently in Edge<br>
&lt;dael> AmeliaBR: Main issue comes up when you have paired colors i n high contrast mode for button. Designed to work together but b/c cascade you get a bg from normal text used with your button text color and contrast falls apart<br>
&lt;dael> AmeliaBR: Other complications are transparency. I've got examples of where we need to say opaque and where we need transparent b/c if opaque obseures things it shouldn't<br>
&lt;dael> AmeliaBR: There are cases where option B fixes and option A causes problems<br>
&lt;RRSAgent> I have made the request to generate https://www.w3.org/2020/04/01-css-minutes.html fantasai<br>
&lt;dael> AmeliaBR: If we follow option A [reads]<br>
&lt;RRSAgent> I have made the request to generate https://www.w3.org/2020/04/01-css-minutes.html fantasai<br>
&lt;dael> AmeliaBR: In my example I have an svg element inside a button that doesn't have a ua background color and I have a custom style div in a button. These would not get reverted colors...Option a forces to canvas color which would be very bad for some schemes.<br>
&lt;dael> AmeliaBR: In option B bg color is calc after inheriting out foreground and finding all elements have button foreground and therefore if they get a bg it needs to be button. Also extra magic about if author supplied foreground was opaque or transparent<br>
&lt;dael> astearns: So one vote for option B.<br>
&lt;dael> AmeliaBR: Option B for me. Option A would cause problems<br>
&lt;dael> Rossen_: Did you try with non-buttons?<br>
&lt;dael> AmeliaBR: No, but it's child elements inside. Child in link is only other case where you'd see it.<br>
&lt;dael> astearns: Argument for option A Rossen_ ?<br>
&lt;dael> Rossen_: Just trying to understand more.<br>
&lt;dael> astearns: Any arguments for option A?<br>
&lt;TabAtkins> I'm thinking B.<br>
&lt;dael> Rossen_: Curious if fantasai has caught up<br>
&lt;dael> fantasai: I think AmeliaBR prop gets better results where this matters. It's up to WG. Interested in hearing from implementors. That's main concern is how impl would<br>
&lt;dael> florian: Implicit argument for option A is simplier<br>
&lt;dael> AmeliaBR: Both are complex b/c neither desc by cascade. Both need to look at author stylesheet and then do fixup. Just a case of if they factor in current color<br>
&lt;dael> heycam: Rossen_ was your question if previous issue could be a mech to solve this?<br>
&lt;dael> Rossen_: No....I agree complexity of one or the other is not deciding factor.<br>
&lt;dael> Rossen_: Trying to work through AmeliaBR test cases.<br>
&lt;dael> Rossen_: Not opposed to B if WG feels it's better. We can impl and see what it looks like<br>
&lt;dael> astearns: Not hearing clamoring for A so inclined to resolve on B and see how it goes<br>
&lt;dael> astearns: Objections to resolve on option B?<br>
&lt;dael> RESOLVED: Select Option B [Based on its resulting computed color value, the [computed|used] background-color of an element is forced by matching all channels other than alpha to the appropriate forced background color; which should be the corresponding system background color if color is a system color, and Canvas otherwise.]<br>
&lt;dael> [agenda wrangling]<br>
&lt;fantasai> https://drafts.csswg.org/css-color-adjust-1/#changes<br>
&lt;dael> astearns: Objections to publish update WD of css color-adjust-1?<br>
&lt;dael> AmeliaBR: Nice to do other issue before, but we're publishing often.<br>
&lt;dael> fantasai: We should publish early and often<br>
&lt;dael> AmeliaBR: 4883 changes are mostly in color so yeah. no objections<br>
&lt;dael> RESOLVED: publish update WD of css-color-adjust-1<br>
</details>


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Received on Wednesday, 1 April 2020 23:48:28 UTC