From 3660aaac85e6be571c238e969d9cf5ca598e4215 Mon Sep 17 00:00:00 2001
From: Jonas Jenwald <jonas.jenwald@gmail.com>
Date: Mon, 17 May 2021 14:34:08 +0200
Subject: [PATCH] Tweak `adjustToUnicode` to allow extending a built-in
 /ToUnicode map

*This is somewhat similiar to the recent changes, in PR 13277, for fonts with an /Encoding entry.*

Currently we're *completely* ignoring the `builtInEncoding`, from the font data itself, for fonts which have a built-in /ToUnicode map.
While it (obviously) doesn't seem like a good idea in general to simply overwrite existing built-in /ToUnicode entries, it should however not hurt to use the `builtInEncoding` to supplement *missing* /ToUnicode entires.
---
 src/core/fonts.js | 23 ++++++++++++++---------
 1 file changed, 14 insertions(+), 9 deletions(-)

diff --git a/src/core/fonts.js b/src/core/fonts.js
index 8b8ec434d..b391ab693 100644
--- a/src/core/fonts.js
+++ b/src/core/fonts.js
@@ -135,9 +135,6 @@ function adjustToUnicode(properties, builtInEncoding) {
   if (properties.isInternalFont) {
     return;
   }
-  if (properties.hasIncludedToUnicodeMap) {
-    return; // The font dictionary has a `ToUnicode` entry.
-  }
   if (builtInEncoding === properties.defaultEncoding) {
     return; // No point in trying to adjust `toUnicode` if the encodings match.
   }
@@ -147,11 +144,17 @@ function adjustToUnicode(properties, builtInEncoding) {
   const toUnicode = [],
     glyphsUnicodeMap = getGlyphsUnicode();
   for (const charCode in builtInEncoding) {
-    if (
-      properties.hasEncoding &&
-      properties.differences[charCode] !== undefined
-    ) {
-      continue; // The font dictionary has an `Encoding`/`Differences` entry.
+    if (properties.hasIncludedToUnicodeMap) {
+      if (properties.toUnicode.has(charCode)) {
+        continue; // The font dictionary has a `ToUnicode` entry.
+      }
+    } else {
+      if (
+        properties.hasEncoding &&
+        properties.differences[charCode] !== undefined
+      ) {
+        continue; // The font dictionary has an `Encoding`/`Differences` entry.
+      }
     }
     const glyphName = builtInEncoding[charCode];
     const unicode = getUnicodeForGlyph(glyphName, glyphsUnicodeMap);
@@ -159,7 +162,9 @@ function adjustToUnicode(properties, builtInEncoding) {
       toUnicode[charCode] = String.fromCharCode(unicode);
     }
   }
-  properties.toUnicode.amend(toUnicode);
+  if (toUnicode.length > 0) {
+    properties.toUnicode.amend(toUnicode);
+  }
 }
 
 class Glyph {