This affects various Microsoft products that use child windows, and is an accessibility bug for users because focus is lost when they interact with an app and the active element is moved in DOM by React.

React version: 18.3.1

Steps To Reproduce

1. Clone the repro repo https://github.com/ling1726/react-child-window-focus-repro
2. Run npm install
3. Run npm run dev
4. Open the demo app in http://localhost:5173/
5. Reorder the items with ArrowUp and ArrowDown
6. Open example in child window
7. Reorder the items with ArrowUp and ArrowDown
8. Notice that focus is lost immediately after reordering

Recording:

Link to code example: https://github.com/ling1726/react-child-window-focus-repro

The current behavior

The current getActiveElementDeep always uses the global window keyword. Note this snippet is from the React codebase

This fails focus restore when the active element is moved by React because it never gets the correct active element in a child window.

The expected behavior

When React moves an active element it should restore focus to the active element in a child window