import type { CustomFontFamily } from '../types.js';
/** The family that stands in for `family`'s faces without a file, by its
 *  name (case-insensitive), or undefined. A family never stands in for
 *  itself. */
export declare function fontFallbackOf(customFonts: readonly Pick<CustomFontFamily, 'name' | 'fallback'>[] | undefined, family: string): string | undefined;
/** The families of `customFonts` that name a fallback, as `{ family,
 *  fallback, variants }` (the faces the family has files for, which are
 *  not set in the fallback). */
export declare function fontFallbackFamilies(customFonts: readonly Pick<CustomFontFamily, 'name' | 'fallback' | 'variants'>[] | undefined): {
    family: string;
    fallback: string;
    variants: readonly {
        weight: number;
        style: 'normal' | 'italic';
    }[];
}[];
/** Whether the family has a file of this slant. A family with files only
 *  sets in its fallback the slant it has none of (an italic it lacks); a
 *  family with no file at all sets every face in it. A weight between the
 *  family's own files is left to the browser's matching, as it is for any
 *  family. */
export declare function hasOwnStyle(variants: readonly {
    weight: number;
    style: 'normal' | 'italic';
}[], style: 'normal' | 'italic'): boolean;
/** The open family that stands in for `family` in a file that leaves the
 *  app (an EPUB, an HTML export, an SVG picture inside one; #993), or
 *  undefined. The family is one the book may not hand on
 *  (`redistributable: false`) and names a `fallback`: its files stay out of
 *  the file, and the fallback's faces of the same weight and slant go in
 *  under its name, so the reading system sets the text in a face of about
 *  the same width instead of in whatever it has. A fallback is open by
 *  definition (it is what the licensed family's bundle ships in its place),
 *  which is what lets it travel. */
export declare function exportStandInOf(customFonts: readonly Pick<CustomFontFamily, 'name' | 'fallback' | 'redistributable'>[] | undefined, family: string): string | undefined;
//# sourceMappingURL=fallback.d.ts.map