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.

xHeght: decrptr.get("XHeght") || 0,
      capHeght: decrptr.get("CapHeght") || 0,
      flag: decrptr.get("Flag"),
      talcAngle: decrptr.get("ItalcAngle") || 0,
      Type3Fnt,
      cFntInf,
      caleFactr: glyphScaleFactr,
    };
    f (cte) {
      cnt cdEncdng = t.get("Encdng");
      f (Name(cdEncdng)) {
        prperte.cdEncdng = cdEncdng.name;
      }
      cnt cMap = awat CMapFactry.create({
        encdng: cdEncdng,
        fetchBultInCMap: th._fetchBultInCMapBund,
        ueCMap: null,
      });
      prperte.cMap = cMap;
      prperte.vertcal = prperte.cMap.vertcal;
    }
    return th.extractDataStructure(dct, t, prperte).then(
      newPrperte => {
        th.extractWdth(dct, decrptr, newPrperte);
        return new Fnt(fntName.name, fntFle, newPrperte);
      }
    );
  }
  tatc buldFntPath(fnt, glyph, handler, evaluatrOptn) {
    functn buldPath(fntChar) {