/**
 * Overlay animation tokens (XC-11).
 *
 * Single JS source of truth that mirrors the CSS custom properties in
 * `style/interaction.css`. Svelte transitions need numeric inputs at the
 * call site, so we expose the same values as constants here and as
 * runtime getters that read the live CSS custom property — useful when
 * a consumer overrides a token via `BlocksProvider` or a theme.
 *
 * Components should call `getOverlayMotion()` (returns the resolved
 * numeric values for the current document) over hard-coding numbers.
 * The optional `override` argument carries per-instance values from a
 * component's `transitionDuration` / `transitionEasing` props.
 *
 * Reduced motion: `getOverlayMotion()` reads the live CSS — so the
 * `@media (prefers-reduced-motion: reduce)` branch in `interaction.css`
 * automatically collapses durations and distances to zero. Components
 * never need to consult the media query themselves.
 */
export type EasingFn = (t: number) => number;
export interface OverlayMotion {
    /** Enter duration in ms (panel + backdrop). */
    enterDuration: number;
    /** Exit duration in ms (panel + backdrop). */
    exitDuration: number;
    /** Backdrop enter duration in ms — usually = enterDuration. */
    backdropEnterDuration: number;
    /** Backdrop exit duration in ms — usually = exitDuration. */
    backdropExitDuration: number;
    /** Easing for panel and backdrop transitions. */
    easing: EasingFn;
    /** Panel scale-in start value (0..1). 1 disables the scale effect. */
    panelScaleStart: number;
    /** Panel fly-in distance in px (translated along the placement axis). */
    panelFlyDistance: number;
}
export interface OverlayMotionOverride {
    enterDuration?: number;
    exitDuration?: number;
    backdropEnterDuration?: number;
    backdropExitDuration?: number;
    easing?: EasingFn;
    panelScaleStart?: number;
    panelFlyDistance?: number;
}
/** Defaults mirror the CSS custom properties in `interaction.css`. */
export declare const OVERLAY_MOTION_DEFAULTS: OverlayMotion;
/**
 * Longest `transition-duration` currently applying to an element, in ms.
 *
 * Used by Popover's exit-motion lag: the panel's CSS transition (token-driven,
 * per-instance-overridable, collapsed by reduced motion) is the single source
 * of truth for how long closed content must stay mounted, so the lag is read
 * from the live computed style instead of duplicating the token resolution in
 * JS. Returns `0` when the element is missing, has no transition, or the
 * environment has no CSS engine (SSR, jsdom) — callers then tear down
 * synchronously, which keeps unstyled consumers and node tests on the
 * pre-motion behaviour.
 *
 * `transition-duration` computes to a comma list (one entry per transition
 * property); the max governs because the exit isn't over until the slowest
 * property lands.
 */
export declare function maxTransitionDurationMs(el: Element | null | undefined): number;
/**
 * Read the current overlay motion settings.
 *
 * SSR-safe: when `window` is unavailable, returns the static defaults.
 * Easing is not read from CSS (no portable cross-browser parse of
 * `cubic-bezier()` arguments) — it stays at the JS default and can be
 * overridden per-instance via the `override` argument.
 */
export declare function getOverlayMotion(override?: OverlayMotionOverride): OverlayMotion;