[css-env] Add environment variables defined in WebKit

[SebastianZ]

In #6729, @heycam was tasked to provide a list of environment variables WebKit implements, which should be standardized. @tabatkins asked for that list to be able to publish a FPWD.

From reading the related code, it looks like the missing environment variables are:

• fullscreen-inset-top
• fullscreen-inset-left
• fullscreen-inset-bottom
• fullscreen-inset-right
• fullscreen-auto-hide-duration

@heycam, @fantasai Should those be added to the spec.? Are there any other variables not listed here?

Sebastian

[nt1m]

Maybe @jernoble or @eric-carlson have thoughts

[bramus]

In #6729 (comment), @smfr confirmed that the extra envvars mentioned at the start of this thread is correct.

AFAICT these are not documented anywhere. The only reference I could find was a mention in this “What’s new in Safari and WebKit” PDF from WWDC 2018. There is no video that accompanies this deck (or at least I could not find one at https://developer.apple.com/videos/wwdc2018/):

UPDATE: Did find #2871 here in the repo (which didn’t show up through a Google search). These envvars were discussed back in the day, but there was no resolution to actually add them.