astro/dist/assets/fonts/logic/optimize-fallbacks.js

Astro is a modern site builder with web best practices, performance, and DX front-of-mind.

import { isGenericFontFamily, unifontFontFaceDataToProperties } from "../utils.js";
async function optimizeFallbacks({
  family,
  fallbacks: _fallbacks,
  collectedFonts,
  enabled,
  systemFallbacksProvider,
  fontMetricsResolver
}) {
  let fallbacks = [..._fallbacks];
  if (fallbacks.length === 0 || !enabled || collectedFonts.length === 0) {
    return null;
  }
  const lastFallback = fallbacks[fallbacks.length - 1];
  if (!isGenericFontFamily(lastFallback)) {
    return null;
  }
  const localFonts = systemFallbacksProvider.getLocalFonts(lastFallback);
  if (!localFonts || localFonts.length === 0) {
    return null;
  }
  if (localFonts.includes(family.name)) {
    return null;
  }
  const localFontsMappings = localFonts.map((font) => ({
    font,
    // We must't wrap in quote because that's handled by the CSS renderer
    name: `${family.nameWithHash} fallback: ${font}`
  }));
  fallbacks = [...localFontsMappings.map((m) => m.name), ...fallbacks];
  let css = "";
  for (const { font, name } of localFontsMappings) {
    for (const collected of collectedFonts) {
      css += fontMetricsResolver.generateFontFace({
        metrics: await fontMetricsResolver.getMetrics(family.name, collected),
        fallbackMetrics: systemFallbacksProvider.getMetricsForLocalFont(font),
        font,
        name,
        properties: unifontFontFaceDataToProperties(collected.data)
      });
    }
  }
  return { css, fallbacks };
}
export {
  optimizeFallbacks
};