On Wed, Sep 15, 2021 at 2:55 PM Mike Taylor <[email protected]> wrote:
> Hey Rune, > > Is there any way for developers to know behavior has changed on their > sites when this ships? (Or alternatively, any clues for folks triaging > bugs, besides bisecting?). > > I'm wondering about sites where breakage is pretty bad. Would it be useful > to ship a devtools issue (probably overkill given the use counter data, > especially if they're over-counting problematic cases...)? > You mean adding a devtools warning if the propagated values would have been different without containment? I think the background and overflow scrollbar propagation would have pretty obvious effects. If the body direction/writing-mode is orthogonal to the root html direction/writing-mode, such effects would be more subtle and harder to spot. We have changed how body/html/viewport propagation for orthogonal writing-modes have been done before without any such signals/warnings (not sure if we even have done intent-to-ship for that). (Also, I asked dholbert if he thinks it's something Gecko would want to > ship in https://bugzilla.mozilla.org/show_bug.cgi?id=1730763#c2) > Thanks! Positive response from dholbert. On 9/14/21 6:12 PM, Rune Lillesveen wrote: > > Contact emails [email protected] > > Specification http://drafts.csswg.org/css-contain-1/#c3 > > Summary > > Used values for contain different from none on the root or body elements > will disable propagation of CSS properties from body as per > specification[1]. [1] https://drafts.csswg.org/css-contain-1/#c3 > > This change was brought to the CSSWG because the unconditionally > propagating body styles to the viewport would create circular dependencies > for CSS Container Queries. For instance, a propagated writing-mode from > body to the viewport, when orthogonal to the outer, could change the size > of root element which in turn could affect style resolution for body via > container queries, which again could result in a different computed > writing-mode for body. See the github issue for details: > https://github.com/w3c/csswg-drafts/issues/5913. It should be noted that > the CSSWG has regretted introducing propagation from body and have > resolved > <https://github.com/w3c/csswg-drafts/issues/6079#issuecomment-816307011> > on not introducing new properties to be propagated from body. > > The implementation was added to M93 behind a flag along with use counters > for used contain values different from none on html root and body: > > https://chromestatus.com/metrics/feature/timeline/popularity/3936 > https://chromestatus.com/metrics/feature/timeline/popularity/3937 > > These use counters cover more cases than potentially problematic ones, as > they do not detect if the styles are different on body and root and would > make any differences. Still the use counters are low - 0.0004% and 0.0008% > respectively. > > Blink component Blink>CSS > <https://bugs.chromium.org/p/chromium/issues/list?q=component:Blink%3ECSS> > > TAG review None. Change to a W3C Recommendation in the CSSWG. > > TAG review status Not applicable > > Risks > Interoperability and Compatibility > > - Not shipping this change would block shipping CSS Container Queries, > or cause stateful style/layout issues. > - Low use counters for containment on body and root. > - There is an interop risk if the other engines do not change their > implementations. The use counters indicate that, at least at the moment, > applying containment to root and body is rare. > > I have not filed a standards position for Gecko. This seems like a > rather small change compared to APIs typically filed as a > standards position. I got a quick reply on the webkit-thread. > Issues are filed for both browsers and I have triaged the failing tests on > wpt.fyi accordingly. > > Gecko: No signals https://bugzilla.mozilla.org/show_bug.cgi?id=1730763 > > WebKit: No objection: > https://lists.webkit.org/pipermail/webkit-dev/2021-September/031982.html > > Web developers: No signals > > > -- Rune Lillesveen -- You received this message because you are subscribed to the Google Groups "blink-dev" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CACuPfeSk22%3D%2Bn%3DSuG%2BK8p%2BYKA%3DLE4AoZ7516LkddzARZp7_yhA%40mail.gmail.com.
