/**
 * System font discovery for PDF generation.
 *
 * When no embedded font is provided and the document contains non-WinAnsi
 * characters, this module searches standard system font directories for a
 * TrueType font (.ttf or .ttc) with broad Unicode coverage.
 *
 * This is a Node.js-only feature — browser environments do not have
 * file system access and must always provide fonts explicitly.
 *
 * .ttc (TrueType Collection) files are supported — parseTtf() extracts
 * the first font from the collection automatically.
 *
 * Discovery is exposed both as a generator
 * ({@link iterateSystemFontCandidates}) for early-exit callers and as
 * an array snapshot ({@link discoverSystemFontCandidates}) for tests
 * and full enumeration. Once the full snapshot has been produced it is
 * cached and replayed on subsequent calls; partial iterations rely on
 * the OS page cache to make repeat reads of the same font files cheap.
 */
/**
 * Lazily yield discoverable system font candidates, in preference order.
 *
 * Each entry is the raw font file bytes of a `.ttf` or `.ttc` file.
 * The caller decides which candidate to use (e.g. by checking cmap coverage).
 *
 * Iterating one candidate at a time lets callers `break` as soon as
 * they find a match, avoiding the cost of recursively reading every
 * font in every system font directory just to discard them.
 */
export declare function iterateSystemFontCandidates(): Generator<Uint8Array, void, void>;
/**
 * Return all discoverable system font candidates, ordered by preference.
 *
 * Each entry is the raw font file bytes of a `.ttf` or `.ttc` file.
 * The caller decides which candidate to use (e.g. by checking cmap coverage).
 *
 * The full snapshot is cached: once produced, repeated calls return the
 * same array without touching the filesystem.
 *
 * Prefer {@link iterateSystemFontCandidates} when you only need the
 * first candidate that satisfies a predicate: it avoids reading every
 * font in every system directory just to discard them.
 */
export declare function discoverSystemFontCandidates(): Uint8Array[];
/**
 * Search for a system font suitable for Unicode rendering.
 *
 * Returns the raw font file bytes of the highest-priority candidate,
 * or `null` if no font was found.
 */
export declare function discoverSystemFont(): Uint8Array | null;
/**
 * Reset the cached font discovery result (for testing).
 */
export declare function resetFontDiscoveryCache(): void;
/**
 * Override the cached candidates with a custom list (for testing).
 * Call {@link resetFontDiscoveryCache} to clear the override.
 */
export declare function _setCandidatesForTest(candidates: Uint8Array[]): void;