/**
 * The `@font-face` rules a subject is set in.
 *
 * Applicability pruning keeps the rules that match an element, and a face
 * matches none: it names a file, and the element names the face. Pruned with
 * the rest, it left a render document whose `font-family` asked for a face
 * nobody declared — which every renderer answers with whatever it has
 * installed. So a page that ships its own font was painted in the fallback, and
 * a change to that font moved no image.
 *
 * A face is carried when a family it declares is in the computed `font-family`
 * of something the subtree paints, generated boxes of its frame included
 * (`paintedStyles`), which is the pruning question asked of the one
 * rule that cannot be asked it directly. Its files are named against the page,
 * not against the sheet that declared them, because the render document has one
 * inline sheet and a base: `url(../fonts/a.woff2)` written in
 * `/assets/site.css` resolves against the page there, and fetches nothing.
 */
export interface IndexedFace {
    /** The family the face answers for, folded the way family names match. */
    readonly family: string;
    /** The rule as the render document carries it, every `url()` against the page. */
    readonly text: string;
    /** Every file the face names, absolute. */
    readonly sources: readonly string[];
    /**
     * Whether the host kept the face's `src`.
     *
     * jsdom's CSSOM keeps `font-family` on a face and nothing else, so a face read
     * there declares a family and no file. Carrying it would paint the fallback
     * under a declaration that says otherwise.
     */
    readonly readable: boolean;
}
export declare function isFontFaceRule(rule: CSSRule): rule is CSSFontFaceRule;
/**
 * One face, read from the sheet it sits in.
 *
 * `base` is what the sheet's own relative URLs resolve against: its `href`, or
 * the document's base for a sheet with none.
 */
export declare function faceOf(rule: CSSFontFaceRule, base: string, document: Document): IndexedFace | null;
/** The faces a subtree is set in, in the order the document declared them. */
export declare function facesUsedBy(root: Element, faces: readonly IndexedFace[]): readonly IndexedFace[];
/**
 * Every family named in the computed `font-family` of these styles.
 *
 * The whole stack, not the face that won: which entry a glyph is drawn from is
 * the renderer's to decide from the faces it holds, and a face left out because
 * an earlier entry was installed here is a face missing wherever it is not.
 */
export declare function familiesPaintedWith(styles: readonly CSSStyleDeclaration[]): ReadonlySet<string>;
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