[csswg-drafts] [css-color-adjust] Properties to control backplates? (#5038)

chrishtr has just created a new issue for https://github.com/w3c/csswg-drafts:

== [css-color-adjust] Properties to control backplates? ==
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](https://github.com/MicrosoftEdge/MSEdgeExplainers/blob/master/Accessibility/HighContrast/explainer.md) for screenshots and details.

Please view or discuss this issue at https://github.com/w3c/csswg-drafts/issues/5038 using your GitHub account