import { type ChatHeightCache } from './chatMeasurement.svelte.js';
import type { ScrollAnchor } from './chatTypes.js';
export type VisualAnchor = ScrollAnchor;
export type CaptureVisualAnchorArgs<T> = {
    messages: T[];
    getMessageId: (_message: T) => string;
    heightCache: ChatHeightCache;
    estimatedHeight: number;
    visibleStart: number;
    topGap: number;
    headerHeight: number;
    scrollTop: number;
};
export type RestoreVisualAnchorArgs<T> = {
    anchor: VisualAnchor;
    messages: T[];
    getMessageId: (_message: T) => string;
    heightCache: ChatHeightCache;
    estimatedHeight: number;
    topGap: number;
    headerHeight: number;
};
/**
 * Capture the first visible message as a visual anchor before late layout
 * growth, so users scrolled away from bottom keep the same content in view.
 */
export declare const captureVisualAnchor: <T>(args: CaptureVisualAnchorArgs<T>) => VisualAnchor | null;
/**
 * Calculate the scrollTop that restores a captured visual anchor.
 */
export declare const restoreVisualAnchor: <T>(args: RestoreVisualAnchorArgs<T>) => number | null;