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Re: [csswg-drafts] anything that creates a stacking context should sort in the positioned descendants z-ordering list

From: L. David Baron via GitHub <sysbot+gh@w3.org>
Date: Fri, 01 Jun 2018 01:55:58 +0000
To: public-css-archive@w3.org
Message-ID: <issue_comment.created-393735225-1527818157-sysbot+gh@w3.org>
To answer some of the questions I was trying to address with the testcase:

1\. Is creating a stacking context equivalent to sorting in the positioned descendants list?  (Basically, does the first test column agree with the following two?)
  * in Chrome and WebKit, these are equivalent
  * in Gecko, they're equivalent except that `isolation` and `will-change` don't trigger sorting in the positioned descendants list, but do create a stacking context
  * in Edge, the exception is `mask-image` (in the same way)

2\. What *implemented* properties don't cause creation of a stacking context in implementations but are specified to do so?
  * In all 4 engines, `transform-style: flat`
  * in WebKit, also `clip-path` `mask` (though they actually *do* as values of `will-change`)
  * in Chromium, `mask` (and also broken as a value of `will-change`), and `will-change: contain` (but not `contain` itself)
  * in Edge, `mask`

3\. What properties create a containing block for fixed-positioned elements?
  * in Gecko:
    * all the transform things (`transform`, `perspective`, `transform-style: preserve-3d`) that create stacking contexts (Gecko doesn't yet implement `translate`, `rotate`, and `scale`)
    * `filter`
    * (plus some other properties that are not actually enabled but their [`will-change` support is inadvertently enabled](https://bugzilla.mozilla.org/show_bug.cgi?id=1466008))
  * in Chromium:
    * all the transform things (the Gecko list plus `translate`, `rotate`, and `scale`) that create stacking contexts
  * in WebKit:
    * only `transform`
  * in Edge:
    * all the transform things (same list as Chromium) that create stacking contexts

GitHub Notification of comment by dbaron
Please view or discuss this issue at https://github.com/w3c/csswg-drafts/issues/2717#issuecomment-393735225 using your GitHub account
Received on Friday, 1 June 2018 01:56:07 UTC

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