Behaviour of not-rendered elements

[jakearchibald]

When we look for elements to transition, it feels like we should ignore not-rendered elements.

For example, I think creating a transition from:

<div style="page-transition-tag: foo">hello</div>
<div style="page-transition-tag: foo; display: none">world</div>

…to:

<div style="page-transition-tag: foo; display: none">hello</div>
<div style="page-transition-tag: foo">world</div>

…should be valid. As in, it shouldn't fail due to the repeated use of page-transition-tag: foo, since only one of them is renderable.

This also means we wouldn't create transition pseudo-elements for elements that are not-rendered on both sides of the transition.

As in, a transition from:

<div style="page-transition-tag: foo; display: none">hello</div>

…to:

<div style="page-transition-tag: foo; display: none">world</div>

…would not create ::page-transition-container(foo).

This seems to fit in with the model where we don't create CSS animations for not-rendered elements.

[khushalsagar]

The spec has been updated to ignore such elements, as if they were not tagged. Note that if the not rendered state changes midway through a transition then we still consider the tag on this element.