1998269 - table-wrapper box should use 'opacity' from table box

Status: NEW

(Core :: Layout: Tables, defect)

Description

[Daniel Holbert [:dholbert]]

The css-tables-3 draft spec says (emphasis added):

3.6.1. Overrides applying in all modes

The following rules apply to all tables, irrespective of the layout mode in use.

The computed values of properties position, float, margin-*, top, right, bottom, and left on the table are used on the table-wrapper box and not the table grid box; the same holds true for the properties whose use could force the used value of transform-style to flat (see list) and their shorthands/longhands relatives: this list currently includes overflow, opacity, filter, clip, clip-path, isolation, mask-*, mix-blend-mode, transform-* and perspective.

https://drafts.csswg.org/css-tables-3/#global-style-overrides

We don't currently apply the table's opacity to its table-wrapper box, and that disagrees with other browsers and this spec text (and I think it happens to cause bug 1998159, which is how I ran across this).

We need to fix this, though it's not as simple as just inheriting opacity to the table-wrapper-box -- if we did that, then e.g. opacity:0.5 would stack on the table-wrapper and the table and result in us painting the contents at an effective opacity of 0.25.

As the spec text notes, really we should just be painting the table-wrapper box using the opacity of the table, and then painting the table box with an opacity of 1. (And we could do this with inherit combined with a special-case for the table, potentially.)

Comment 1

[Daniel Holbert [:dholbert]]

Attachment: testcase 1

Here's a testcase.

EXPECTED RESULTS:
Each 'caption' should have the same opacity as its corresponding table.

ACTUAL RESULTS:
Each 'caption' is fully opaque.

Comment 2

[Daniel Holbert [:dholbert]]

Chrome 143.0.7475.7 (Official Build) dev (64-bit) and Safari 26 give EXPECTED RESULTS.

Firefox 146.0a1 (2025-10-28) gives ACTUAL RESULTS.
(and our behavior goes back ~forever; e.g. Nightly 46 2016-01-01 also gives ACTUAL RESULTS)