Attach (recommended) or Link to PDF file here:
[example.pdf](https://github.com/mozilla/pdf.js/files/6916129/example.pdf)

Configuration:
- Web browser and its version: Chrome, Firefox
- Operating system and its version: all
- PDF.js version: various versions, including 2.11.54
- Is a browser extension: no

Screenshot with visible textLayer:
![Screenshot from 2021-08-02 13-05-03](https://user-images.githubusercontent.com/6362989/127844878-f85e291f-2060-4028-be09-7835f32ccfaa.png)

Which means some letters at the beginning/end of text selection are missing when copying text.

}
        
        
        forcePostTable = true;
      } else {
        
        
        
        
        
        
        
        
        
        
        for (let i = 0; i < cmapMappingsLength; ++i) {
          let charCode = cmapMappings[i].charCode;
          if (
            cmapPlatformId === 3 &&
            charCode >= 0xf000 &&
            charCode <= 0xf0ff
          ) {
            charCode &= 0xff;
          }
          charCodeToGlyphId[charCode] = cmapMappings[i].glyphId;
        }
      }
      
      if (
        properties.glyphNames &&