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.

FormatError,
  info,
  isNum,
  shadow,
  string32,
  warn,
} from "../shared/util.js";
import { CFFCompiler, CFFParser } from "./cff_parser.js";
import {
  FontFlags,
  getFontType,
  MacStandardGlyphOrdering,
  normalizeFontName,
  recoverGlyphName,
  SEAC_ANALYSIS_ENABLED,
} from "./fonts_utils.js";
import { getDingbatsGlyphsUnicode, getGlyphsUnicode } from "./glyphlist.js";
import {
  getEncoding,
  MacRomanEncoding,
  StandardEncoding,
  SymbolSetEncoding,
  ZapfDingbatsEncoding,
} from "./encodings.js";
import {
  getGlyphMapForStandardFonts,
  getNonStdFontMap,
  getStdFontMap,
  getSupplementalGlyphMapForArialBlack,
  getSupplementalGlyphMapForCalibri,