/**
 * Settle gate for a CSS transition: call back once the transition of
 * `property` on `element` has actually ended.
 *
 * A fixed timer measured from the moment the target value is applied
 * lands at the same wall-clock offset whether or not the transition has
 * started, but the transition only starts at the first style recalc
 * after the value lands — on a busy main thread (a gallery's first
 * layout, a big thumbnail decode) that can be well past the offset.
 * Anything gated on the fixed timer then fires mid-flight.
 *
 * Contract:
 * - No `transitionstart` within `fallbackMs` → the element is not
 *   transitioning (reduced motion, identity transform, no CSS) and the
 *   gate settles on the timer, exactly like the fixed timer did.
 * - `transitionstart` re-bases the timer on the real start; `transitionend`
 *   settles immediately. Interrupted transitions (`transitioncancel`)
 *   leave the timer running so a restart still settles in time.
 * - Events bubbling from descendants, or for other properties, are
 *   ignored. The callback runs at most once.
 *
 * Returns a disposer; disposing after settle is a no-op.
 */
export interface TransitionSettleEvent {
    target: unknown;
    propertyName?: string;
}
/** Structural slice of a DOM element: headless carries no DOM lib. */
export interface TransitionSettleTarget {
    addEventListener(type: string, listener: (event: TransitionSettleEvent) => void): void;
    removeEventListener(type: string, listener: (event: TransitionSettleEvent) => void): void;
}
export declare function onTransitionSettle(element: TransitionSettleTarget, property: string, fallbackMs: number, callback: () => void): () => void;