[csswg-drafts] [css-view-transitions-1] Should mix-blend-mode be a part of the ua opacity animation? (#8924)

vmpstr has just created a new issue for https://github.com/w3c/csswg-drafts:

== [css-view-transitions-1] Should mix-blend-mode be a part of the ua opacity animation? ==
This is somewhat related to [ISSUE 4](https://drafts.csswg.org/css-view-transitions/#issue-c760166d) in the spec. We currently specify mix-blend-mode conditionally if we have a crossfade. 

This, however, has unintended and sometimes surprising effects for developers trying to customize old/new animations. @argyleink had an example where the old content did a slide out to the left and new content did a slide in from the left: the overlap between the two contents did not "look right", since the expectation is to see a normal blend mode.

My suggestion is to consider putting mix-blend-mode to be a part of the UA animation instead, maybe something like

```
@keyframes -ua-mix-blend-mode-plus-lighter {
  from { mix-blend-mode: plus-lighter }
  to { mix-blend-mode: plus-lighter }
}
```
and adding that into the animation-name for ua generated css. As an aside, mix-blend-mode is not animatable, but would need to be at least discretely animatable for this to work.

It's a bit of a hack, but I worry that having mix-blend-mode that is added for pairs automatically may cause more developer pain.

Any thoughts?


Please view or discuss this issue at https://github.com/w3c/csswg-drafts/issues/8924 using your GitHub account


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Received on Tuesday, 6 June 2023 17:50:44 UTC