Re: [csswg-drafts] [css-view-transitions-1] Should isolation and plus-lighter blending be applied conditionally (#7814)

The CSS Working Group just discussed `[css-view-transitions-1] Should isolation and plus-lighter blending be applied conditionally`, and agreed to the following:

* `RESOLVED: isolation/blending-mode properties are added conditionally, as stated in current spec`

<details><summary>The full IRC log of that discussion</summary>
&lt;TabAtkins> khush: There's some styles in the UA CSS that are applied when you have both old and new image<br>
&lt;TabAtkins> khush: One is isolation on the image pair, th eother is blend mode on the images, plus-lighter<br>
&lt;TabAtkins> khush: This means if the two pixels you're blending are same value it's a no-op<br>
&lt;TabAtkins> khush: You only really need the isolation to get this two-image crossfade tho<br>
&lt;TabAtkins> khush: If you have only an incoming or outgoing, just fading in/out, you don't need this complex blending<br>
&lt;TabAtkins> khush: As an engine you can detect this and optimize<br>
&lt;TabAtkins> khush: We weren't sure - authors might add a background to things and force us to the offscreen-blending like with two images, authors might not realize they're falling off to a slow path<br>
&lt;TabAtkins> khush: So proposal is only apply these styles when both images are present. When only one is, don't apply isolation or blending<br>
&lt;TabAtkins> khush: Just like in a custom-authored webpage, you'd only add what you need. If authors do need some complex blending they can add it themselves.<br>
&lt;fantasai> This seems fine...<br>
&lt;emeyer> TabAtkins: My only potential concern is isolation has containing-block effects<br>
&lt;emeyer> …But I’m not certain if that’s an important effect or not<br>
&lt;TabAtkins> khush: the image pair element already has abspos, it'll have the same CB effect<br>
&lt;emeyer> TabAtkins: In most cases, you aren’t positioning the images themselves<br>
&lt;emeyer> …If there’s an iossue, it’s in a funky corner case I’m not concerned with<br>
&lt;TabAtkins> khush: The size flows thru the group, the image pair uses the group as its CB so it sees that size. That's why we added abspos to make sure the CB hierarchy happens regardless of isolation<br>
&lt;emeyer> TabAtkins: There’s a few things that will skip abspos but won’t skip isolation<br>
&lt;emeyer> …so I think that’s fine<br>
&lt;TabAtkins> astearns: So are we reoslving to just accept the current spec?<br>
&lt;TabAtkins> khush: Yes.<br>
&lt;TabAtkins> astearns: Objections to accepting Khushal's edits?<br>
&lt;TabAtkins> RESOLVED: isolation/blending-mode properties are added conditionally, as stated in current spec<br>
</details>


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Received on Wednesday, 12 April 2023 16:42:48 UTC