/**
 * Imperative animation primitives shared by the motion engines.
 *
 * The engines run outside React: they observe host markup and mark it, and they
 * cannot re-render a component to replay an entrance. Every entrance is
 * therefore imperative, because a CSS @starting-style transition only fires on
 * an element's FIRST style resolution - and the host forces one while it mounts
 * a row or a panel (layout effects, scroll-into-view, measurement) before the
 * observer microtask can mark the element.
 *
 * Every helper degrades to a no-op where the environment has no Web Animations
 * API (jsdom), so the engines stay testable through their class markers.
 */
/** Easing shared with motion.module.css: fast start, long settle. */
export declare const EASE_GLIDE = "cubic-bezier(0.22, 1, 0.36, 1)";
/** Easing for opacity-only work. */
export declare const EASE_FADE = "cubic-bezier(0.33, 1, 0.68, 1)";
/**
 * Landing curves written with `linear()`, because `cubic-bezier()` cannot
 * overshoot and settle.
 *
 * EASE_SETTLE is the reference spring-settle curve (3% peak) for travel and
 * scale entrances that arrive repeatedly - a row settles instead of stopping
 * dead, without turning into jitter. EASE_SPRING is sampled from an underdamped
 * response `1 - e^(-zeta*w*t) * (cos(wd*t) + (zeta*w/wd) * sin(wd*t))` at
 * zeta 0.62 (~8% peak): it belongs to low-frequency surfaces (the settings
 * panel, a welcome screen) where visible weight reads as quality and there is
 * no repetition to make it noisy. Opacity-only work keeps EASE_FADE, since an
 * overshooting alpha flickers.
 */
export declare const EASE_SETTLE = "linear(0, 0.32 8%, 0.79 20%, 1.03 30%, 1.01 46%, 1)";
export declare const EASE_SPRING = "linear(0, 0.108 7.1%, 0.338 14.3%, 0.588 21.4%, 0.8 28.6%, 0.95 35.7%, 1.038 42.9%, 1.077 50%, 1.083 57.1%, 1.069 64.3%, 1.049 71.4%, 1.029 78.6%, 1.012 85.7%, 1.001 92.9%, 1)";
/** Whether the element can run an imperative animation here. */
export declare function canAnimate(el: Element): boolean;
/** Whether the user asked the platform for reduced motion. */
export declare function prefersReducedMotion(): boolean;
/** Pure: the reduced-motion variant of an entrance - opacity only. */
export declare function reducedFrames(frames: readonly Keyframe[]): Keyframe[];
/**
 * Play an entrance on an element. A previous entrance on the same element is
 * cancelled first, so a rapid replay retargets from the live value instead of
 * stacking; host animations on that element are left alone.
 *
 * \`fill: 'backwards'\` holds the start frame across a stagger delay - without it
 * the element would paint at its resting style and then jump to the start.
 * @param el - the element to animate.
 * @param frames - the entrance keyframes (the first frame is the start state).
 * @param options - timing; a duration is required.
 * @returns the started animation, or null where animation is unavailable.
 */
export declare function replayEntrance(el: HTMLElement, frames: readonly Keyframe[], options: KeyframeAnimationOptions): Animation | null;
/**
 * Resolve once the element's transitions settle, or after \`timeoutMs\` when none
 * fires (reduced motion, a hidden element, jsdom). The bound keeps a close path
 * from stalling on a transition that never starts.
 * @param el - the element whose transitions to await.
 * @param timeoutMs - upper bound in milliseconds.
 * @returns a promise that settles when the element reaches its target style.
 */
export declare function whenTransitionSettles(el: HTMLElement, timeoutMs: number): Promise<void>;