1792016 - Focusout event related target not set appropriately on Mac builds?

Status: UNCONFIRMED

(Core :: DOM: UI Events & Focus Handling, defect)

Description

[Luke A. Leber]

User Agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/105.0.0.0 Safari/537.36

Steps to reproduce:

With the following markup:

<div class="links">
  <a href="#">Link 1</a>
  <a href="#">Link 2</a>
</div>

attach a focusout event listener to .links:

document.querySelector('.links').addEventListener('focusout', e => {
  console.log(e.relatedTarget);
});

now use the keyboard to tab from Link 1 to Link 2

Actual results:

e.relatedTarget is null, but only for the Mac build of Firefox.

Windows, Linux, and Android builds all print out "Link 2" as the related target!

Expected results:

Printing out e.relatedTarget should match the Windows, Linux, and Android behavior.

Version: 105.0b1
Build ID: 20220822142820
User Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:105.0) Gecko/20100101 Firefox/105.0
OS:

Comment 1

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

The Bugbug bot thinks this bug should belong to the 'Core::Widget: Cocoa' component, and is moving the bug to that component. Please correct in case you think the bot is wrong.

Comment 2

[Luke A. Leber]

Attachment: Small scale test exhibiting behavior

I think the root cause here might be incorrect.  Here's a more complete POC example:

```

```

Comment 3

[Luke A. Leber]

As it stands, the two links within the drop-button list are completely keyboard inaccessible out of the box on Mac builds of Firefox. This may have to do with differences in how <button> and <a> elements receive focus on this platform (tab key vs arrow keys).

Comment 4

[Luke A. Leber]

Attachment: Third example is the charm (instructions included)...sorry for the noise.

Sorry for the noise.  This is a land of confusion.

Updated instructions and example.

Comment 5

[Luke A. Leber]

Sorry for the noise. This is a land of confusion.

Updated instructions and example.