builder now has opentype sanitiser

OTFbuild/build_font.py

@@ -70,6 +70,24 @@ def main():
         no_features=args.no_features,
     )
 
+    # Run OpenType Sanitizer to catch issues browsers would reject
+    try:
+        import ots
+        print("\nRunning OpenType Sanitizer...")
+        result = ots.sanitize(args.output, capture_output=True)
+        if result.returncode == 0:
+            print("  OTS: passed")
+        else:
+            print(f"  OTS: FAILED (exit code {result.returncode})", file=sys.stderr)
+            if result.stderr:
+                for line in result.stderr.decode().strip().splitlines():
+                    print(f"    {line}", file=sys.stderr)
+            sys.exit(1)
+    except ImportError:
+        print("\nWarning: opentype-sanitizer not installed, skipping OTS validation",
+              file=sys.stderr)
+        print("  Install with: pip install opentype-sanitizer", file=sys.stderr)
+
 
 if __name__ == "__main__":
     main()

OTFbuild/font_builder.py

@@ -53,6 +53,10 @@ def _should_have_cmap(cp):
         return True
     if 0x1B000 <= cp <= 0x1B16F:
         return True
+    # Unicode noncharacters — never map these (U+FFFE, U+FFFF are reserved;
+    # format 4 cmap uses 0xFFFF as a sentinel, so mapping it causes OTS rejection)
+    if cp >= 0xFFFE and cp <= 0xFFFF:
+        return False
     # Everything in standard Unicode ranges (up to 0xFFFF plus SMP)
     if cp <= 0xFFFF:
         return True

OTFbuild/requirements.txt

@@ -1,2 +1,3 @@
 fonttools>=4.47.0
 brotli>=1.1.0
+opentype-sanitizer>=9.2.0