How do the "overlaid half-open views" work?

[Wittmaxi]

How does this "half folded out" view work?

(here: the search view)
How is it rendered and would this be possibly a cleaner way to implement the Find/Replace Overlay instead of creating a new shell shadowing the editor?

[wimjongman]

What you see is the fly-out view.

Select the viewstack in the trim area an tick "Show in the original location"