in app/addons/components/components/ace-worker-mango.js [596:606]
this.clipRows = function (firstRow, lastRow) {
if (this.end.row > lastRow)
var end = { row: lastRow + 1, column: 0 };
else if (this.end.row < firstRow)
var end = { row: firstRow, column: 0 };
if (this.start.row > lastRow)
var start = { row: lastRow + 1, column: 0 };
else if (this.start.row < firstRow)
var start = { row: firstRow, column: 0 };
return Range.fromPoints(start || this.start, end || this.end);
};