[css-color-adjust] Properties to control backplates?

[chrishtr]

The Chromium implementation of forced-colors mode puts a backplate behind all text [1] so that readability of the text is guaranteed.

When a browser is in dark mode (either via a forced dark mode, or developer opt-in), there are cases where backplates are desired. For example, if there is text meant to overlay an image, contrast between the text and image may not be good enough; developers may also appreciate the convenience of a UA-supplied backplate.

Proposal: have a CSS property that controls whether the backplate is present. Maybe user agents could be allowed by default to apply backplates, and color-adjust: exact would opt-out? This would prioritize usability of the page over developer styling, which sounds right to me.

@minorninth

[1] See this explainer for screenshots and details.

[tabatkins]

Proposing we push this to level 2, as it seems useful, but not worth delaying CR for level 1 on designing this.

[tabatkins]

@chrishtr Are you okay with us pushing this to level 2?

[chrishtr]

I'm ok with that. Thanks for asking.