Function measureLine

mini-code-edit/cm/lib/codemirror.js:1579–1594

(line, ch)

    var tempId = "CodeMirror-temp-" + Math.floor(Math.random() * 0xffffff).toString(16);
    function measureLine(line, ch) {
      if (ch == 0) return {top: 0, left: 0};
      var wbr = options.lineWrapping && ch < line.text.length &&
                spanAffectsWrapping.test(line.text.slice(ch - 1, ch + 1));
      measure.innerHTML = "<pre>" + line.getHTML(makeTab, ch, tempId, wbr) + "</pre>";
      var elt = document.getElementById(tempId);
      var top = elt.offsetTop, left = elt.offsetLeft;
      // Older IEs report zero offsets for spans directly after a wrap
      if (ie && top == 0 && left == 0) {
        var backup = document.createElement("span");
        backup.innerHTML = "x";
        elt.parentNode.insertBefore(backup, elt.nextSibling);
        top = backup.offsetTop;
      }
      return {top: top, left: left};
    }
    function localCoords(pos, inLineWrap) {
      var x, lh = textHeight(), y = lh * (heightAtLine(doc, pos.line) - (inLineWrap ? displayOffset : 0));
      if (pos.ch == 0) x = 0;