added fonts

node_modules/@next/font/dist/local/get-fallback-metrics-from-font-file.js

@@ -0,0 +1,86 @@
+"use strict";
+Object.defineProperty(exports, "__esModule", { value: true });
+exports.getFallbackMetricsFromFontFile = void 0;
+// The font metadata of the fallback fonts, retrieved with fontkit on system font files
+// The average width is calculated with the calcAverageWidth function below
+const DEFAULT_SANS_SERIF_FONT = {
+    name: 'Arial',
+    azAvgWidth: 934.5116279069767,
+    unitsPerEm: 2048,
+};
+const DEFAULT_SERIF_FONT = {
+    name: 'Times New Roman',
+    azAvgWidth: 854.3953488372093,
+    unitsPerEm: 2048,
+};
+/**
+ * Calculate the average character width of a font file.
+ * Used to calculate the size-adjust property by comparing the fallback average with the loaded font average.
+ */
+function calcAverageWidth(font) {
+    try {
+        /**
+         * Finding the right characters to use when calculating the average width is tricky.
+         * We can't just use the average width of all characters, because we have to take letter frequency into account.
+         * We also have to take word length into account, because the font's space width usually differ a lot from other characters.
+         * The goal is to find a string that'll give you a good average width, given most texts in most languages.
+         *
+         * TODO: Currently only works for the latin alphabet. Support more languages by finding the right characters for additional languages.
+         *
+         * The used characters were decided through trial and error with letter frequency and word length tables as a guideline.
+         * E.g. https://en.wikipedia.org/wiki/Letter_frequency
+         */
+        const avgCharacters = 'aaabcdeeeefghiijklmnnoopqrrssttuvwxyz      ';
+        // Check if the font file has all the characters we need to calculate the average width
+        const hasAllChars = font
+            .glyphsForString(avgCharacters)
+            .flatMap((glyph) => glyph.codePoints)
+            .every((codePoint) => font.hasGlyphForCodePoint(codePoint));
+        if (!hasAllChars)
+            return undefined;
+        const widths = font
+            .glyphsForString(avgCharacters)
+            .map((glyph) => glyph.advanceWidth);
+        const totalWidth = widths.reduce((sum, width) => sum + width, 0);
+        return totalWidth / widths.length;
+    }
+    catch {
+        // Could not calculate average width from the font file, skip size-adjust
+        return undefined;
+    }
+}
+function formatOverrideValue(val) {
+    return Math.abs(val * 100).toFixed(2) + '%';
+}
+/**
+ * Given a font file and category, calculate the fallback font override values.
+ * The returned values can be used to generate a CSS @font-face declaration.
+ *
+ * For example:
+ * @font-face {
+ *   font-family: local-font;
+ *   src: local(Arial);
+ *   size-adjust: 90%;
+ * }
+ *
+ * Read more about this technique in these texts by the Google Aurora team:
+ * https://developer.chrome.com/blog/font-fallbacks/
+ * https://docs.google.com/document/d/e/2PACX-1vRsazeNirATC7lIj2aErSHpK26hZ6dA9GsQ069GEbq5fyzXEhXbvByoftSfhG82aJXmrQ_sJCPBqcx_/pub
+ */
+function getFallbackMetricsFromFontFile(font, category = 'serif') {
+    const fallbackFont = category === 'serif' ? DEFAULT_SERIF_FONT : DEFAULT_SANS_SERIF_FONT;
+    const azAvgWidth = calcAverageWidth(font);
+    const { ascent, descent, lineGap, unitsPerEm } = font;
+    const fallbackFontAvgWidth = fallbackFont.azAvgWidth / fallbackFont.unitsPerEm;
+    let sizeAdjust = azAvgWidth
+        ? azAvgWidth / unitsPerEm / fallbackFontAvgWidth
+        : 1;
+    return {
+        ascentOverride: formatOverrideValue(ascent / (unitsPerEm * sizeAdjust)),
+        descentOverride: formatOverrideValue(descent / (unitsPerEm * sizeAdjust)),
+        lineGapOverride: formatOverrideValue(lineGap / (unitsPerEm * sizeAdjust)),
+        fallbackFont: fallbackFont.name,
+        sizeAdjust: formatOverrideValue(sizeAdjust),
+    };
+}
+exports.getFallbackMetricsFromFontFile = getFallbackMetricsFromFontFile;