Private OptionalcurrentPrivate ReadonlydepsThe item whose overlay is currently open, or undefined.
Private ReadonlyonPrivaterefreshRe-derive the open flyout's tooltip-flip class from the live viewport.
PrivateisWhether any of the item's flyout toggles is currently active.
Re-sync each chip's active-state for the open flyout of item (no-op otherwise).
Open a vertical panel popover anchored to btn, hosting the rich controls
built by the item's popover.build. Mirrors the flyout's glass surface +
real-child arrow, but flows content vertically and vertically clamps within
the viewport (popovers can be tall).
Close the open overlay (if any), running its teardown + returning focus.
Close the overlay if a pointerdown landed outside it (and its opener).
PrivatetopA button's top edge in the rail root's coordinate space — what an
absolutely positioned popover/flyout child of the root needs for
style.top. Equals btn.offsetTop while the items wrapper is
layout-transparent (fine pointers), and stays correct when the wrapper is
a scroll box (coarse pointers), where offsetTop would ignore its
scrollTop.
Tear down the overlay (rail disposal).
The currently-open overlay (chip flyout OR panel popover) + its DOM, or undefined when none is open.
teardownis the popover builder's cleanup (undefined for chip flyouts).