Description

Fixes: #28880
Alternative to #28658.

I added a useEffect-like cleanup pattern to useMergeRefs, which allows something to be cleaned up more easily than with the current way ref callbacks work. Ref callbacks are normally called with null when a new one is called, but unless you set the node as a property of the ref callback, you don't have access to it. It's probably possible to do, but it makes the code much harder to understand than the useEffect pattern that everyone already knows. So if a ref callback returns a cleanup function, we'll call the cleanup function instead of calling the callback a second time with null. It's still possible to have the old behaviour by simply not returning a cleanup function. I think this pattern will be very useful for many components switching from an effect hook to a ref callback.

How has this been tested?

Screenshots

Types of changes

Checklist:

• My code is tested.
• My code follows the WordPress code style.
• My code follows the accessibility standards.
• My code has proper inline documentation.
• I've included developer documentation if appropriate.
• I've updated all React Native files affected by any refactorings/renamings in this PR.