export declare let focusVisible: boolean;
export declare function setFocusVisible(value: boolean): void;
/**
 * Recursively walks the DOM tree, piercing Shadow DOM boundaries and
 * resolving slots, to find the first tabbable element.
 *
 * TODO: consider use document.createTreeWalker which might be faster, yet more
 *       complex in code; may find references in the core/experimental/popup
 *       before the commit that added this function
 */
export declare function getFirstTabbable(root: Element | DocumentFragment): HTMLElement | null;