export type WindowRange = {
    /** First mounted index (inclusive). */
    start: number;
    /** One past the last mounted index (exclusive). */
    end: number;
};
/**
 * Pure windowing math: given each section's height (px), the scroll offset, the
 * viewport height, and an overscan count, return the `[start, end)` index window
 * to mount. Robust to a zero viewport (a headless/pre-layout pass) — it then
 * mounts a small overscan window anchored at the item under `scrollTop` rather
 * than the whole list.
 */
export declare function computeWindowRange(heights: readonly number[], scrollTop: number, viewport: number, overscan: number): WindowRange;
export type WindowedSections = {
    /** Attach to the scroll container. */
    scrollRef: React.RefObject<HTMLDivElement | null>;
    /** The mounted window `[start, end)`. */
    range: WindowRange;
    /** Prefix offsets: `offsets[i]` is the top px of section `i`; `offsets[count]`
     *  is the total content height. */
    offsets: number[];
    /** Total content height (px) — set on the spacer so scroll length is stable. */
    totalHeight: number;
    /** Report a MOUNTED section's real height (px) so the layout refines as async
     *  content — e.g. Pierre's Shiki render — grows. Drive it from a ResizeObserver;
     *  a zero/idle value is ignored so a headless pass keeps the estimate. */
    measure: (index: number, height: number) => void;
    /** Scroll section `index` to the top of the pane (the rail-jump). */
    scrollToIndex: (index: number) => void;
};
/**
 * Variable-height section windowing over a scroll container. Seeds every section
 * to `estimateHeight(i)`, mounts only `range`, and refines heights from real
 * measurements (a no-op in a zero-layout headless pass, which keeps the estimate
 * — deterministic for tests). Pass a STABLE `estimateHeight` (wrap in useCallback).
 */
export declare function useWindowedSections(opts: {
    count: number;
    estimateHeight: (index: number) => number;
    overscan?: number | undefined;
}): WindowedSections;