/**
 * Drilldown trail.
 *
 * A drilldown with no visible way back is a trap: the reader clicks California,
 * the map becomes counties, and nothing on screen says where they are or how to
 * leave. The trail is therefore rendered by default rather than left to the host
 * application, and every level except the current one is a real `<button>`, so it
 * is reachable by keyboard and announced as a control rather than as decoration.
 *
 * Rendered above the plot, in the flow, so it cannot cover geography. A floating
 * overlay would sit on top of exactly the part of the map the reader just zoomed
 * into.
 *
 * @module components/Breadcrumb
 */
export interface Crumb {
    label: string;
    /** Levels to climb when this crumb is chosen. 0 is the current level. */
    up: number;
}
export declare class Breadcrumb {
    readonly container: HTMLElement;
    readonly onSelect: (up: number) => void;
    private nav;
    constructor({ container, onSelect }: {
        container: HTMLElement;
        onSelect: (up: number) => void;
    });
    /** Render a trail, or remove it when there is nothing to go back to. */
    render(crumbs: readonly Crumb[]): void;
    destroy(): void;
}
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