[css-view-transitions-1] Removing the root element should probably skip the transition synchronously

[emilio]

If during an animating view transition you replace the root element, then the originating element of the pseudo-element tree is disconnected, so you can't reasonably do stuff like computing styles with it or what not.

The spec doesn't mention what happens in this case. It probably should skip the transition?

Another alternative could be for the view transition pseudos to be reparented somehow (once / if there's a new root?), but that seems error prone and I don't think there's any use case for that.

Context for it is https://bugzilla.mozilla.org/show_bug.cgi?id=1963212 fwiw.

cc @vmpstr @noamr

[noamr]

In this case, the transition would be skipped in the next frame because of https://www.w3.org/TR/css-view-transitions-1/#handle-transition-frame step 4. The transition is skipped when there is no active animation, which would be the case here.

[emilio]

@noamr but what if you add a new root element and somehow the styles so that there's an animation? Or is your interpretation that since you removed the parent of the view transition pseudo tree (and thus the view transition pseudo-tree itself) then there's no pseudo-tree and thus no animation?

[noamr]

@noamr but what if you add a new root element and somehow the styles so that there's an animation? Or is your interpretation that since you removed the parent of the view transition pseudo tree (and thus the view transition pseudo-tree itself) then there's no pseudo-tree and thus no animation?

Yea, the pseudo-tree was attached to the old document element here and the new one doesn't have a pseudo-tree and thus no animation, so the view transition would be skipped in the next frame. Is that sufficiently specified?