Consider a ttf font with both Symbolic and Nonsymbolic flags set with a Differences array in the encoding dict as non-symbolic

It fixes #20232.

src/core/evaluator.js

@@ -3661,8 +3661,24 @@ class PartialEvaluator {
     if (baseEncodingName) {
       properties.defaultEncoding = getEncoding(baseEncodingName);
     } else {
-      const isSymbolicFont = !!(properties.flags & FontFlags.Symbolic);
+      let isSymbolicFont = !!(properties.flags & FontFlags.Symbolic);
       const isNonsymbolicFont = !!(properties.flags & FontFlags.Nonsymbolic);
+
+      // The PDF specs state that the flags Symbolic and Nonsymbolic must be
+      // mutually exclusive. However, some fonts are marked as both.
+      // In that case we ignore the Symbolic flag when there is a Differences
+      // entry (which indicates that the font is used as a non-symbolic
+      // font).
+      if (
+        properties.type === "TrueType" &&
+        isSymbolicFont &&
+        isNonsymbolicFont &&
+        differences.length !== 0
+      ) {
+        properties.flags &= ~FontFlags.Symbolic;
+        isSymbolicFont = false;
+      }
+
       // According to "Table 114" in section "9.6.6.1 General" (under
       // "9.6.6 Character Encoding") of the PDF specification, a Nonsymbolic
       // font should use the `StandardEncoding` if no encoding is specified.

test/pdfs/.gitignore

@@ -743,3 +743,4 @@
 !tracemonkey_with_editable_annotations.pdf
 !bug1980958.pdf
 !tracemonkey_annotation_on_page_8.pdf
+!issue20232.pdf

test/test_manifest.json

@@ -13028,5 +13028,12 @@
     "md5": "ae4f643ee9bb0fd725277a9d1e0fb1df",
     "rounds": 1,
     "type": "load"
+  },
+  {
+    "id": "issue20232",
+    "file": "pdfs/issue20232.pdf",
+    "md5": "cc53e96a8fd9eafbfbb74de564f37047",
+    "rounds": 1,
+    "type": "eq"
   }
 ]