/**
 * Configuration for the backdrop helper
 */
export interface BackdropConfig {
    /** Whether the backdrop is static (clicking it does not close the sheet) */
    isStatic: boolean;
    /** Invoked when the backdrop is clicked */
    onClick: () => void;
}
/**
 * Backdrop helper for BootstrapSheet.
 *
 * Owns the backdrop DOM element lifecycle: creation, opacity updates during
 * drag and animation, and removal. Behavioral decisions (hide vs shake on
 * click) stay with the orchestrator via the `onClick` callback.
 */
export default class Backdrop {
    #private;
    constructor(config: BackdropConfig);
    /**
     * Get the backdrop DOM element
     * @returns The element, or null when the backdrop is not shown
     */
    get element(): HTMLElement | null;
    /**
     * Create the backdrop element and append it to the document body.
     * Does nothing if the backdrop is already shown.
     */
    show(): void;
    /**
     * Update backdrop opacity
     * @param ratio - Opacity ratio (clamped to [0, 1])
     */
    setOpacity(ratio: number): void;
    /**
     * Let pointer events through the backdrop, or catch them again.
     *
     * An undimmed sheet is a non-modal presentation: with no dimming there is
     * no affordance that the area outside is a dismissal target, and the page
     * behind stays interactive.
     * @param interactive - Whether the backdrop should receive pointer events
     */
    setInteractive(interactive: boolean): void;
    /**
     * Remove the backdrop element from the DOM
     */
    dispose(): void;
}
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