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There's actual gamut mapping of wide-gamut colors in Firefox Nightly- I'm going to play around with it a bit and see how it's working. It's in Firefox Nightly 153, by setting layout.css.gamut-mapping.method to 2.

From the first glance, things are looking good- way better than clipping! I'm using the apps.colorjs.io/gamut-mappin... tool to do some comparison. None is the browser's GMA, compared to the Raytrace and CSS (Binary Search) algorithms, and then naive clipping (which is what is active in browsers).

CSS Color 4 specifies 3 algorithms that can be used, and Firefox implemented Binary Search (in the gradients tool as "CSS") and Ray Trace. I'm testing out Ray Trace, which is a bit faster yet not as precise.

Now things are getting interesting. It looks like the color `oklch(90% .1 20)` is getting rendered by Firefox much more lavender than expected, and doesn't match the ColorJS implementation. Note the final step here is inside rec2020, while everything else is outside, which may be why.

The jump to lavender seems to be happening right on the edge of the gradient- I "zoomed in" on the gradient, with linear-gradient(to right, oklch(90% 0.11 375.67), oklch(90% .1 20)), and there's a sudden jump to lavender right at the end.

By default, gradients are interpolated in Oklab. Switching to OkLCh shows another oddity, with a random jump to a bluish green.