Rich text: check the selection first in ownsSelection

[ellatrix]

What?

Reorders ownsSelection so the selection-containment check runs before the editing-host checks.

Follow-up to #80549 (merged). That one read the contentEditable attribute to drop the forced layout, but didn't move the typing metric. This tries the other axis: ordering.

Why?

ownsSelection runs once per editable per keystroke. Under editableRoot the host is the canvas wrapper, which contains every editable element, so the host checks (contentEditable reads + contains) pass for every instance and don't tell them apart. Only the selection does.

With the host checks first, each of the ~N non-owning instances does two contentEditable reads and an activeElement.contains( element ) walk before reaching the check that eliminates it. Doing the discriminating check first lets them bail sooner.

How?

Move the anchor/focus containment check ahead of the host checks. A non-owning instance now returns after one element.contains( anchorNode ), instead of also doing the two contentEditable reads and the activeElement.contains( element ) walk.

Same boolean, behavior unchanged. This is purely about the order of cheap checks; the forced-layout read is already gone in trunk via #80549.

Testing Instructions

1. Behavior is unchanged: ownsSelection returns the same value for the same state.
2. npm run test:unit packages/rich-text passes.
3. Watch the type metric on codevitals for whether the reordering alone moves it.

Use of AI Tools

Written with the help of Claude Code.

[github-actions]

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Co-authored-by: ellatrix <ellatrix@git.wordpress.org>
Co-authored-by: Mamaduka <mamaduka@git.wordpress.org>

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[github-actions]

Size Change: 0 B

Total Size: 7.75 MB

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[ellatrix]

I think we should merge #80549 first and see, then maybe reorder if necessary. #80549 is the better fix, we should avoid forcing layout

[Mamaduka]

Don't have a strong opinion on merge order.

[Mamaduka]

Unfortunately, there are no changes to typing metrics after #80549 was merged - https://codevitals.run/public/WordPress/gutenberg/metrics?metric=type.

Let's rebase and try this one as well.

[ellatrix]

So has nothing to do with layout? 🤔

[github-actions]

Flaky tests detected in 2fa1316.
Some tests passed with failed attempts. The failures may not be related to this commit but are still reported for visibility. See the documentation for more information.

🔍 Workflow run URL: https://github.com/WordPress/gutenberg/actions/runs/29969133947
📝 Reported issues:

• [Flaky Test] should cut and paste individual blocks with collapsed selection #80248 in /test/e2e/specs/editor/various/copy-cut-paste.spec.js