/**
 * Anchor positioning for top-layer popovers. See
 * `notes/architecture/positioning.md` for the full model.
 *
 * Two runtime paths: CSS Anchor Positioning (modern browsers) and a JS
 * fallback that measures the trigger and writes `top`/`left`.
 *
 * Both paths honour `offset.gap` and `offset.crossAxisShift`. The
 * CSS path passes the values through as strings; the JS fallback resolves
 * them to pixels via a hidden DOM probe (see `resolveCssLengthToPixels`)
 * so tokens, `calc()`, `var()`, etc all work. The JS fallback hides the
 * popover with `opacity: 0` until the first measurement completes, so it
 * is never painted at the wrong location.
 */
import { type RefObject } from 'react';
import { type TPlacementOptions } from '../internal/resolve-placement';
/**
 * Hook that positions an element relative to an anchor element using
 * CSS Anchor Positioning (with a JS fallback for older browsers).
 *
 * This hook is the positioning primitive. It has no knowledge of popovers,
 * visibility, or animation. Compose it with `Popover` for anchor-positioned
 * top-layer content.
 *
 * When CSS Anchor Positioning is supported, it sets CSS properties
 * (`anchor-name`, `position-anchor`, `position-area`, `position-try-fallbacks`)
 * directly on the elements via `el.style.setProperty()`.
 *
 * When not supported, it falls back to JavaScript-based positioning using
 * `position: fixed` with measured coordinates, re-running on scroll (capture)
 * and resize events.
 */
export declare function useAnchorPosition({ anchorRef, popoverRef, placement, forceFallbackPositioning, isEnabled, isOpen, }: {
    /**
     * Element to position relative to.
     */
    anchorRef: RefObject<HTMLElement | null>;
    /**
     * Element being positioned (typically a popover).
     *
     * The popover host may be unmounted between opens (the `Popover`
     * primitive unmounts after its exit animation). Pass `isOpen` so the
     * positioning effect re-runs against the freshly mounted element on
     * the next open. Without it, the effect's bound listeners and styles
     * would target the previous (detached) element.
     */
    popoverRef: RefObject<HTMLElement | null>;
    /**
     * Where to place the element relative to the anchor.
     * `offset.gap` and `offset.crossAxisShift` are part of the
     * placement object.
     *
     * All fields are optional. Omitted fields fall back to:
     *   - `axis`: `'block'`
     *   - `edge`: `'end'`
     *   - `align`: `'center'`
     *   - `offset.gap`: `token('space.100', '8px')`
     *   - `offset.crossAxisShift.value`: `'0px'`
     *   - `offset.crossAxisShift.direction`: `'forwards'`
     *
     * The full default placement (`{}`) renders the popover centered
     * below the trigger with one `space.100` of gap and no cross-axis
     * shift.
     *
     * `offset.gap` and `offset.crossAxisShift.value` accept either a
     * number (pixels) or a CSS length string (eg `token('space.200')`).
     */
    placement?: TPlacementOptions;
    /**
     * Forces the JavaScript positioning fallback even when the browser
     * supports CSS Anchor Positioning. Useful for testing fallback
     * behavior in any environment, including production.
     */
    forceFallbackPositioning?: boolean;
    /**
     * When `false`, the hook is a no-op and applies no positioning.
     * Defaults to `true`.
     */
    isEnabled?: boolean;
    /**
     * Whether the popover is currently open. Drives a re-run of the
     * positioning effect when the popover host element is unmounted
     * and remounted across open cycles, so listeners and styles are
     * always wired to the live host element.
     */
    isOpen: boolean;
}): void;