import { RefObject } from 'react';
export interface UseOverlayArgs {
    /** Whether the overlay is currently visible. Everything below is set up while this is true. */
    isActive: boolean;
    /** The overlay panel. Focus is trapped inside it and Escape is scoped to it. */
    containerRef: RefObject<HTMLElement | null>;
    /** Called when Escape is pressed while this is the topmost overlay. Omit to not handle Escape. */
    onEscape?: () => void;
    /**
     * Keep Tab inside the panel and restore focus to the previously focused element on close, unless
     * an overlay opened after this one is still open.
     */
    trapFocus?: boolean;
    /** Prevent the page behind the overlay from scrolling. */
    lockScroll?: boolean;
}
/**
 * The three behaviours every blocking overlay needs: Escape to dismiss, a focus trap, and a
 * scroll lock on the page behind it.
 *
 * They share one module-level stack because they share one question: overlays nest (a
 * ConfirmModal opened from inside a Modal), every instance listens on `document`, and only the
 * innermost one may react. Without the stack, Escape would close every open layer at once and
 * the outer trap would yank focus out of the inner panel on the next Tab.
 *
 * The scroll lock is reference-counted for the same reason: the page stays locked until the last
 * overlay closes, and the body's original inline styles are restored rather than cleared.
 */
export declare function useOverlay({ isActive, containerRef, onEscape, trapFocus, lockScroll }: UseOverlayArgs): void;