import type * as unifont from 'unifont';
import type { FontMetricsResolver, SystemFallbacksProvider } from '../definitions.js';
import type { FontFileData, ResolvedFontFamily } from '../types.js';
export interface CollectedFontForMetrics extends FontFileData {
    data: Partial<unifont.FontFaceData>;
}
export declare function optimizeFallbacks({ family, fallbacks: _fallbacks, collectedFonts, enabled, systemFallbacksProvider, fontMetricsResolver, }: {
    family: Pick<ResolvedFontFamily, 'name' | 'nameWithHash'>;
    fallbacks: Array<string>;
    collectedFonts: Array<CollectedFontForMetrics>;
    enabled: boolean;
    systemFallbacksProvider: SystemFallbacksProvider;
    fontMetricsResolver: FontMetricsResolver;
}): Promise<null | {
    css: string;
    fallbacks: Array<string>;
}>;