Re: [webkit-dev] content-visibility (Was Re: Request For Position on CSS containment)

[cathiechen via webkit-dev]

Hi Tyler,
Thanks for pointing this out!

> On 23 Dec 2021, at 12:23 AM, Tyler Wilcock  wrote:
> 
> Regarding accessibility, there’s a link in your Google doc that states:
> 
> In Chromium 85-89, off-screen children within content-visibility: auto were 
> marked as invisible. In particular, headings and landmark roles were not 
> exposed to accessibility tools. In Chromium 90 this was updated so that they 
> are exposed.
> 
> Does WebKit have this issue, too?
> 

Sorry, I can’t give you the answer right now. We currently haven’t started to 
implement the content-visibility: auto yet. Rob has implemented a prototype for 
content-visibility: hidden. I guess that’s a good start:)

Do we have a WPT test for this scenario? This issue is the one we discuss 
about, right? https://github.com/w3c/csswg-drafts/issues/5857 

I guess in the future, we could try to follow up the discussion, and give an 
update here, when it’s done.

Best,
Cathie___
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Re: [webkit-dev] content-visibility (Was Re: Request For Position on CSS containment)

[cathiechen via webkit-dev]

Hi Ryosuke,

> On 25 Jun 2021, at 4:23 AM, Ryosuke Niwa  wrote:
> 
> Please rename the subject when you're going to discuss the work on a new 
> feature.
> 
> On Thu, Jun 24, 2021 at 9:44 AM cathiechen via webkit-dev 
>  wrote:
> We made a lot of progress regarding CSS containment [1].
> Rob and I have finished the layout containment and size containment [2].\o/
> And the patches of paint containment and style containment are ready for 
> review now [3].
> 
> So we think now it's time to move on to content-visibility:
> (https://www.w3.org/TR/css-contain-2/#content-visibility)
> 
> That seems premature. Have we implemented all the perf optimizations for 
> layout, size, & paint containment? I'd rather not start piling on more 
> features before we get to a point where we're happy with the performance of 
> these features.
> 

Thanks for the advice! Yeah, we kept working on the CSS containment 
performance, here is the summary (also sent to the previous thread)
https://docs.google.com/document/d/166CsE0BqOGur1UyeMqxC7OSijeH90R1Pdck54rLgZNU/edit?usp=sharing
 
<https://docs.google.com/document/d/166CsE0BqOGur1UyeMqxC7OSijeH90R1Pdck54rLgZNU/edit?usp=sharing>


> Since content-visibility depends on paint and style containment, we will do 
> some specification research first, then prototype it based on Rob's patches.
> 
> Does the research part also include making a judgement call as to whether 
> it's a good idea at all? It's wholly unclear to me that content-visibility is 
> a feature we'd like to implement in WebKit given its implications to the 
> accessibility and other browser features.
> 

Yeah, while working on the performance, we found CSS Contain improves 
performance inside the containment box, for instance, setting relayout boundary 
to stop dirty layout propagating to ancestor elements. And we think 
content-visibility would improve the performance from outside, for instance, 
skipping painting content that is offscreen. And we asked for help from 
chromium team, they provided us some very positive feedbacks from the 
developers.(Also list in the document)

Regarding the accessibility feature, the values of content-visibility can 
decide whether or not the content is accessible.
And there are over 80 cases in WPT to test the behaviour of content-visibility.
Also we would like to analyse the performance in the future.


Best,
Cathie___
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Re: [webkit-dev] Request For Position on CSS containment

[cathiechen via webkit-dev]

Hello WebKit-dev,

We've been working on CSS Containment performance for a while.
Here is our summary of it, please take a look if you are interested. Thanks!
https://docs.google.com/document/d/166CsE0BqOGur1UyeMqxC7OSijeH90R1Pdck54rLgZNU/edit?usp=sharing
 


Regarding the current state of CSS contain, the implement of layout, size, 
paint and style containment
have been landed [1]. And the CSS contain runtime flag is enabled by default 
now [2]. \o/

[1] https://bugs.webkit.org/show_bug.cgi?id=172026 

[2] https://bugs.webkit.org/show_bug.cgi?id=234020 


Best,
Rob and Cathie___
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Re: [webkit-dev] Request For Position on CSS containment

[cathiechen via webkit-dev]

Hi webkit-dev,

We made a lot of progress regarding CSS containment [1].
Rob and I have finished the layout containment and size containment [2].\o/
And the patches of paint containment and style containment are ready for review 
now [3].

So we think now it's time to move on to content-visibility:
(https://www.w3.org/TR/css-contain-2/#content-visibility)
Since content-visibility depends on paint and style containment, we will do 
some specification research first, then prototype it based on Rob's patches. 
Thank you for your feedback!

[1] https://bugs.webkit.org/show_bug.cgi?id=172026
[2] https://bugs.webkit.org/show_bug.cgi?id=223569, 
https://bugs.webkit.org/show_bug.cgi?id=223570
[3] https://bugs.webkit.org/show_bug.cgi?id=224742, 
https://bugs.webkit.org/show_bug.cgi?id=226458

Best,
Rob and Cathie

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