import type { Nodes } from 'hast';
/**
 * Returns the set of 1-indexed source line numbers that are visible when
 * the rendered code block is collapsed (i.e. the user hasn't clicked
 * "expand"). Mirrors the visibility rule applied at runtime by `<Pre>`:
 *
 *   - Frames whose `data-frame-type` is `'highlighted'`, `'focus'`,
 *     `'padding-top'`, or `'padding-bottom'` are visible.
 *   - When no such emphasis frame exists, only the first frame is shown
 *     (this matches `getInitialVisibleFrames` in `<Pre>`).
 *
 * `tree` must be the output of `parseSource` (a `Root` whose top-level
 * children are frame `Element`s with `'line'` `Element` descendants).
 * Returns an empty set for an empty/invalid tree.
 */
export declare function getInitialVisibleSourceLines(tree: Nodes): Set<number>;