Re: [csswg-drafts] [css-view-transitions-2] Ignore offscreen elements from participating in transitions (#8282)

> I wouldn't do anything regarding the ink overflow. It shouldn't be web observable... so I think the intersection should work according to the IntersectionObserver rules and disregard ink-overflow.

Hmmm, I think there will be cases where disregarding the ink overflow would end up with glitchy behaviour. Like a widget whose shadow is in the viewport. Should we really ignore it? This has come up for IO in the past too: https://github.com/w3c/csswg-drafts/issues/8649. @szager-chromium on that.

I was curious how content-visibility handles this. Looks like it relies on `overflow-clip-margin` (which is developer provides) and uses that [here](https://drafts.csswg.org/css-contain/#close-to-the-viewport:~:text=The%20element%20is%20close%20to%20the%20viewport%3A%20In%20this%20state%2C%20the%20element%20is%20considered%20%22on%2Dscreen%22%3A%20its%20paint%20containment%20box%27s%20overflow%20clip%20edge%20intersects%20with%20the%20viewport%2C%20or%20a%20user%2Dagent%20defined%20margin%20around%20the%20viewport.). Even if the overflow clip edge is further than the actual ink or scroll overflow, we rely on the specified edge.

With VT we intentionally decided not to have paint containment, so that won't work for us.

> Not sure if clip should be something a different attribute. When the whole content is clipped-out, do you want to treat it as an empty image or not have it at all?

Oh I just read what you said carefully and I tend to agree. We should have separate properties which decide whether the element participates in the transition. If it is participating, then a separate property has knobs for deciding how its captured. So omitting `clip` sounds good.

In that regard, maybe the use-case in https://github.com/w3c/csswg-drafts/issues/9354 should eventually be handled by `view-transition-visibility`.

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Received on Monday, 30 October 2023 20:07:59 UTC