This is a regression from #12864. The underscore is now too thin when the document is zoomed in.

URL: https://github.com/mozilla/pdf.js/files/2321540/issue6127.pdf
PDF.js 2.7.526: https://i.imgur.com/T4mIpct.png
PDF.js 2.7.510: https://i.imgur.com/nbwEpGT.png
Adobe Acrobat Reader DC 2020.013.20074: https://i.imgur.com/wDFBf3R.png

The screenshots were taken at 400% zoom.
}
  setFlatness(flatness) {
    
  }
  setGState(states) {
    for (let i = 0, ii = states.length; i < ii; i++) {
      const state = states[i];
      const key = state[0];
      const value = state[1];
      switch (key) {
        case "LW":
          this.setLineWidth(value);
          break;
        case "LC":
          this.setLineCap(value);
          break;
        case "LJ":
          this.setLineJoin(value);
          break;
        case "ML":
          this.setMiterLimit(value);
          break;
        case "D":
          this.setDash(value[0], value[1]);
          break;