Re: [csswg-drafts] [css-color-6] contrast-color() and gamut mapping (#8539)

> @svgeesus @danburzo I just realized an issue with what we're discussing. There can be multiple output devices, and CSS functions cannot return different used values in different output devices (can they?), not to mention the same element, with e.g. a flat background-color can be displayed across multiple screens at the same time. We also cannot ask implementations to gamut map to the intersection of the gamuts, a) because that's nontrivial to calculate and b) because this produces poor user experience (imagine connecting an auxiliary low quality screen to get some more space, and suddenly this affects your viewing experience everywhere!). Perhaps we can just use the gamut of the primary display device, which should be more stable?

I have little experience with the color management pipeline, and I’m not a habitual user of secondary output devices, but a quick test of the [`color-gamut` media feature](https://developer.mozilla.org/en-US/docs/Web/CSS/@media/color-gamut) with an external monitor on macOS reveals that when moving a browser window between screens the `color-gamut` query result reflects the capabilities of the display that hosts the window. (As far as I can tell, macOS doesn’t render windows across screens). I think it makes sense for `contrast-color()` to be consistent with this behavior, that is to use the gamut of the output device to which the browser window is attached. I intuit that cross-device display is managed at a lower level, so that the multi-screen setup presents itself as a single display to higher levels (e.g. the mirrored display assumes the media features of the main display).

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Received on Tuesday, 29 August 2023 12:54:44 UTC