lib/assets/scripts/vendor/codemirror/codemirror.js
function coordsChar(cm, x, y) {
    var doc = cm.view.doc;
    y += cm.display.viewOffset;
    if (y < 0) return {line: 0, ch: 0, outside: true};
    var lineNo = lineAtHeight(doc, y);
    if (lineNo >= doc.size) return {line: doc.size - 1, ch: getLine(doc, doc.size - 1).text.length};
    if (x < 0) x = 0;

    for (;;) {
      var lineObj = getLine(doc, lineNo);
      var found = coordsCharInner(cm, lineObj, lineNo, x, y);
      var merged = collapsedSpanAtEnd(lineObj);
      if (merged && found.ch == lineRight(lineObj))
        lineNo = merged.find().to.line;
      else
        return found;
    }
  }
function coordsChar(cm, x, y) {
    var doc = cm.view.doc;
    y += cm.display.viewOffset;
    if (y < 0) return {line: 0, ch: 0, outside: true};
    var lineNo = lineAtHeight(doc, y);
    if (lineNo >= doc.size) return {line: doc.size - 1, ch: getLine(doc, doc.size - 1).text.length};
    if (x < 0) x = 0;

    for (;;) {
      var lineObj = getLine(doc, lineNo);
      var found = coordsCharInner(cm, lineObj, lineNo, x, y);
      var merged = collapsedSpanAtEnd(lineObj);
      if (merged && found.ch == lineRight(lineObj))
        lineNo = merged.find().to.line;
      else
        return found;
    }
  }
Coords must be lineSpace-local