Bug 259261 – [popover] element within shadow DOM breaks light dismiss calculation

• Component: DOM
• Status: RESOLVED FIXED

[Westbrook]

When a [popover] element that is a descendant of an open [popover] element exists within a shadow DOM, the topmost clicked [popover] element (https://html.spec.whatwg.org/multipage/popover.html#topmost-clicked-popover) calculation is no done with the composed path which causes the descendant [popover] element to close the ancestor [popover] element at open time.

You can repro this here: https://codepen.io/Westbrook/pen/BaGrdoq

With the following code:

<button popovertarget="popover" popovertargetaction="toggle">Toggle</button>
<div id="popover" popover>
  <template shadowrootmode="open">
    Outter
    <button popovertarget="popover-2" popovertargetaction="toggle">Toggle</button>
  <div id="popover-2" popover>
    Inner
  </div>
  </template>
</div>

[Tim Nguyen (:ntim)]

https://searchfox.org/wubkat/rev/3ae98fa2c02b272e3e55c4e0c324d01da17cb5dc/Source/WebCore/dom/Document.cpp#8903

should probably iterate using `parentElementInComposedTree()`.

[Radar WebKit Bug Importer]

<rdar://problem/112410375>

[Tim Nguyen (:ntim)]

Pull request: https://github.com/WebKit/WebKit/pull/16234

[Tim Nguyen (:ntim)]

Submitted web-platform-tests pull request: https://github.com/web-platform-tests/wpt/pull/41251

[EWS]

Committed 266457@main (9336846dfe3b): <https://commits.webkit.org/266457@main>

Reviewed commits have been landed. Closing PR #16234 and removing active labels.

@ntim

Tim, I noticed the result of the introduced test at https://wpt.fyi/results/html/semantics/popovers/popover-light-dismiss-flat-tree.html?label=master&label=experimental&aligned. 

Gecko has the same error report too (with popover enabled). Any idea?