Top layer elements should not be affected by parent layout (e.g. display: table-column or CSS content property)

• Component: Layout and Rendering
• Status: RESOLVED WONTFIX

[Tim Nguyen (:ntim)]

2 main items from https://fullscreen.spec.whatwg.org/#new-stacking-layer :

* If its position property computes to fixed, its containing block is the viewport, and the initial containing block otherwise.

webkit.org/b/84796 imported/w3c/web-platform-tests/html/semantics/interactive-elements/the-dialog-element/removed-element-is-removed-from-top-layer.html [ ImageOnlyFailure ]
webkit.org/b/84796 imported/w3c/web-platform-tests/html/semantics/interactive-elements/the-dialog-element/top-layer-containing-block.html [ ImageOnlyFailure ]
webkit.org/b/84796 imported/w3c/web-platform-tests/html/semantics/interactive-elements/the-dialog-element/top-layer-stacking.html [ ImageOnlyFailure ]

Modal dialogs have position: fixed by default with UA styles hence why it's relevant to those tests, and looking at the results, it's mostly top/bottom/right/left position which look wrong, making me think this is mostly containing block related.

* It is rendered as an atomic unit as if it were a sibling of its root.

Ancestor elements with [...] cannot affect it.

webkit.org/b/84796 imported/w3c/web-platform-tests/html/semantics/interactive-elements/the-dialog-element/modal-dialog-in-replaced-renderer.html [ ImageOnlyFailure ]
webkit.org/b/84796 imported/w3c/web-platform-tests/html/semantics/interactive-elements/the-dialog-element/modal-dialog-in-table-column.html [ ImageOnlyFailure ]

These tests use particular cases like content: url() or display: table-column on the ancestor and open a modal dialog inside.

[Radar WebKit Bug Importer]

<rdar://problem/82186174>

[Tim Nguyen (:ntim)]

The containing block bits have been split out to bug 231292

[Tim Nguyen (:ntim)]

This is the expected behaviour, we should work to get the spec changed.