Disclosure indicators broken under Safari 15 - stuck closed

[enquora]

At least in CPOutlineView, under macOS 12, release candidate 2, disclosure indicators remain closed when clicked.
Currently unable to test under Big Sur using Safari 15 beta.

[cappbot]

Milestone: Someday. Label: #new. What's next? A reviewer should examine this issue.

[enquora]

No errors or warnings shown in Javascript console when control is triggered - it simply doesn't change.
This is in CPOutlineView instances.
It appears to me this is a general problem with handling clicks on the disclosure control.
Behaviour is erratic - sometimes the disclosure control opens or closes, at others it doesn't. Sometimes hidden rows are displayed correct, at other times they aren't.

[daboe01]

@enquora is this still an issue for you?

[enquora]

Just returned to investigating this.
Still unclear if this is a legitimate problem or a problem building the underlying datasource.

[enquora]

Confirming that problem continues in Safari 15. This is using latest commit to master branch of Cappuccino.

Problem not present in Safari 13 or any version of Chrome, Edge or Firefox.
This after at least two updates to Safari 15. Results the same whether in release version of Safari or Safari Technology Preview.

CPOutlineView otherwise functions as expected.

[daboe01]

-#new
+#needs-reduction
+AppKit

[cappbot]

Milestone: Someday. Labels: #needs-reduction, AppKit. What's next? A minimal test app should be created which demonstrates the concern of this issue in isolation.