import { type RefObject } from "react";
/** The measured window rect this module reasons about (x is irrelevant: the trigger
 *  line is horizontal, so only the vertical edge and the degenerate-size check
 *  matter). */
export interface InViewRect {
    /** Distance from the top of the window to the element's top edge. */
    y: number;
    width: number;
    height: number;
}
/**
 * The one structural capability this module needs from a ref. Declared here rather
 * than imported so nothing DOM-shaped or Animated-shaped enters the type surface:
 * React Native's host instances and react-native-web's host nodes both satisfy it
 * (react-native-web attaches measureInWindow to the node in usePlatformMethods),
 * which is what lets one code path serve native and web.
 */
export interface InViewMeasurable {
    measureInWindow(callback: (x: number, y: number, width: number, height: number) => void): void;
}
/**
 * The pure in-view predicate: has an element with this window rect reached the
 * trigger line, given the window height and how far inside the bottom edge
 * (`insetDp`) the element must come before it counts?
 *
 * True means "reveal it". The test is on the element's TOP edge against a horizontal
 * trigger line at `windowHeight - inset`, which gives both cases the once-only
 * contract needs from a single comparison:
 *   - scrolling up from below the fold: the top edge crosses the line, so the reveal
 *     fires while the element is entering, not after it is fully in;
 *   - a page opened already scrolled past the element (a deep link, a restored
 *     scroll position): the top edge is negative, comfortably past the line, so the
 *     content is already revealed instead of stranded invisible above the viewport.
 * The inset is clamped into the window, so even a nonsense inset only ever moves the
 * line to the top of the window rather than off it.
 *
 * Fail-open cases (see the file header) all return true. Exported for unit tests,
 * following the `entranceTranslation` precedent in ./entrance.tsx: the maths is the
 * load-bearing part and is testable with no renderer.
 */
export declare function isRectInView(rect: InViewRect | null | undefined, windowHeight: number, insetDp: number): boolean;
/**
 * Whether the shared sampling timer is currently running. Kit-internal
 * introspection for the tests that assert the ticker starts on the first pending
 * element and stops when the last one resolves; components never read this.
 */
export declare function inViewTickerActive(): boolean;
/**
 * Whether the element behind `ref` has reached the viewport, latched: it flips false
 * to true at most once and never back (see the file header on once-only).
 *
 * `insetDp` is how far inside the bottom edge of the window the element's top must
 * come before it counts, so a caller can require the element to be properly in view
 * rather than one pixel in.
 *
 * `enabled` is the caller's own reason to not observe at all. When false the hook
 * registers nothing, measures nothing, starts no timer, and reports `true`, which is
 * the fail-open answer: a caller that has decided not to watch (Reveal under Reduce
 * Motion) renders its final frame. It is a parameter rather than a Reduce Motion read
 * inside this hook so the accessibility POLICY stays with the component that owns the
 * animation, and this module stays a plain detector.
 *
 * Known imprecision, deliberate: the measurement is against the WINDOW, so an element
 * inside a nested scroll container that is clipped by that container but whose window
 * rect still falls inside the window counts as in view. It errs toward revealing
 * early, which is the direction this primitive is allowed to be wrong in, and the
 * alternative (walking ancestor clip rects) is a large amount of machinery for a
 * decorative entrance.
 */
export declare function useInView(ref: RefObject<InViewMeasurable | null>, insetDp: number, enabled?: boolean): boolean;
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