The rect a floating-element anchor advertises for positioning. Any element may
implement getAnchorRect(): DOMRect to point positioners (a-menu,
a-tooltip) at a sub-region of itself — e.g. a-input returns its .field
box rather than the host, whose box also spans the label / hint, so a menu or
tooltip lines up with the field itself. Elements without it fall back to their
border box (getBoundingClientRect), so this is opt-in and back-compatible.
Shared by a-menu and a-tooltip.
The rect a floating-element anchor advertises for positioning. Any element may implement
getAnchorRect(): DOMRectto point positioners (a-menu,a-tooltip) at a sub-region of itself — e.g.a-inputreturns its.fieldbox rather than the host, whose box also spans the label / hint, so a menu or tooltip lines up with the field itself. Elements without it fall back to their border box (getBoundingClientRect), so this is opt-in and back-compatible. Shared by a-menu and a-tooltip.