[csswg-drafts] [CSSOM-view] The One Trueâ„¢ viewport definition? (#3716)

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

== [CSSOM-view] The One Trueâ„¢ viewport definition? ==
Hello,

I want to define the "Viewport-Width" Client Hint in HTML, and as part of that, want to define strict processing for it, setting its value to the same one as `document.documentElement.clientWidth`.
At the same time,  [clientWidth](https://drafts.csswg.org/cssom-view/#dom-element-clientwidth)'s definition relies on CSSOM's [viewport definition](https://drafts.csswg.org/cssom-view/#viewport) while HTML relies on another [viewport definition](https://drafts.csswg.org/css2/visuren.html#viewport).

Which on those is the "right" one? Is there a good reason to have multiple definitions to the same concept? Halp! :)

Please view or discuss this issue at https://github.com/w3c/csswg-drafts/issues/3716 using your GitHub account