[css-view-transitions-2] ::v-t-old and ::v-t-new should be display:block

[skobes-chromium]

In the global view transition user agent style sheet, the ::view-transition-old and ::view-transition-new elements are position: absolute without an explicit display or inset-inline-start.

Setting position: absolute causes the computed style of display to be block, but the resolution of inset-inline-start: auto uses the static offset determined as if the element had its initial display value, which is inline (illustration).

This can cause problems such as inappropriate horizontal shifting if an ancestor has text-align: center (crbug.com/476120655).

It would be better for the UA style sheet to explicitly set either display: block or inset-inline-start: 0 (or both).

cc @vmpstr

[bramus]

+1 to explicitly setting display: block on those pseudos.

I had done the same suggestion in #13437 (Closed as Duplicate) which I filed after I got reports from authors who are stumbling over this.

[vmpstr]

Adding to async resolution since I don't think this would be controversial.

The proposal is to set ::view-transition-old(*), ::view-transition-new(*) { display: block; } in UA stylesheets

/cc @emilio @nt1m

[emilio]

Seems fine, but FWIW those elements ought to ignore static positioning already per the resolution of #9939 IIRC

[nt1m]

No strong opinion here, seems ok as long as nothing breaks