Function charWidth

static/editor.md/lib/codemirror/lib/codemirror.js:2861–2869

(display)

  // Compute the default character width.
  function charWidth(display) {
    if (display.cachedCharWidth != null) return display.cachedCharWidth;
    var anchor = elt("span", "xxxxxxxxxx");
    var pre = elt("pre", [anchor]);
    removeChildrenAndAdd(display.measure, pre);
    var rect = anchor.getBoundingClientRect(), width = (rect.right - rect.left) / 10;
    if (width > 2) display.cachedCharWidth = width;
    return width || 10;
  }

  // OPERATIONS