Merge pull request #19427 from calixteman/bug1946181

Add some unicode mapping for ligatures when writing the cmap table in the font (bug 1946181)

src/core/fonts.js

@@ -485,6 +485,8 @@ function adjustMapping(charCodeToGlyphId, hasGlyph, newGlyphZeroId, toUnicode) {
   const isInPrivateArea = code =>
     (PRIVATE_USE_AREAS[0][0] <= code && code <= PRIVATE_USE_AREAS[0][1]) ||
     (PRIVATE_USE_AREAS[1][0] <= code && code <= PRIVATE_USE_AREAS[1][1]);
+  let LIGATURE_TO_UNICODE = null;
+
   for (const originalCharCode in charCodeToGlyphId) {
     let glyphId = charCodeToGlyphId[originalCharCode];
     // For missing glyphs don't create the mappings so the glyph isn't
@@ -514,7 +516,23 @@ function adjustMapping(charCodeToGlyphId, hasGlyph, newGlyphZeroId, toUnicode) {
     // glyph ids to the correct unicode.
     let unicode = toUnicode.get(originalCharCode);
     if (typeof unicode === "string") {
-      unicode = unicode.codePointAt(0);
+      if (unicode.length === 1) {
+        unicode = unicode.codePointAt(0);
+      } else {
+        if (!LIGATURE_TO_UNICODE) {
+          LIGATURE_TO_UNICODE = new Map();
+          // The code range [0xfb00, 0xfb4f] contains some ligature characters
+          // but not all.
+          // See https://www.compart.com/en/unicode/block/U+FB00.
+          for (let i = 0xfb00; i <= 0xfb4f; i++) {
+            const normalized = String.fromCharCode(i).normalize("NFKD");
+            if (normalized.length > 1) {
+              LIGATURE_TO_UNICODE.set(normalized, i);
+            }
+          }
+        }
+        unicode = LIGATURE_TO_UNICODE.get(unicode) || unicode.codePointAt(0);
+      }
     }
     if (unicode && !isInPrivateArea(unicode) && !usedGlyphIds.has(glyphId)) {
       toUnicodeExtraMap.set(unicode, glyphId);