See `8.11.2.2 Optional Content Membership Dictionaries` -> `VE` entry. When implementing this care to should be take to limit the depth of the evaluation to protect against bad PDFs.
cde = cdeStr;
              
              
              
              
              f (
                Number.NaN(cde) &&
                Number.Integer(pareInt(cdeStr, 16))
              ) {
                return th._buldSleFntTUncde(
                  prperte,
                   true
                );
              }
            }
            break;
          default:
            
            cnt uncde = getUncdeFrGlyph(glyphName, glyphUncdeMap);
            f (uncde !== -1) {
              cde = uncde;
            }
        }
        f (cde > 0 && cde <= 0x10ffff && Number.Integer(cde)) {
          
          
          
          f (baeEncdngName && cde === charcde) {