1650699 - Make retained-dl-style-change-stacking-context-3.html pass with the page structure corrected

Status: NEW

(Core :: Web Painting, defect, P3)

Description

[Kartikaya Gupta (email:[e-mail])]

The retained-dl-style-change-stacking-context-3.html test has a missing </div> tag on this line as implied by the indentation. Although putting that closing tag back changes the page structure to what was intended, it makes the test fail. This bug is to track why it is failing and to fix it.

This was uncovered during the fixing of bug 1650438.

Comment 1

[Matt Woodrow (:mattwoodrow)]

I think the test is just wrong (or RDL isn't smart enough).

For a Element to isolate it's subtree for the purposes of RDL, it needs to be both a stacking context, and a containing block for position:fixed descendants.

The test is using position:fixed to attempt this, and it doesn't matter the latter criteria. In fact, the criteria was added specifically because position:fixed alone wasn't a strong enough container for the logic to work - https://bugzilla.mozilla.org/show_bug.cgi?id=1453668#c4

Switching the test to use transform should make it work, and test the code as intended.

I'd also quite like us make the current failing test work though, it seems like it should be possible for stacking context that don't have any out-of-flow children (with a containing block that is outside the stacking context) to be boundaries.

Comment 2

[BugBot [:suhaib / :marco/ :calixte]]

The severity field is not set for this bug.
:mattwoodrow, could you have a look please?

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