demo/marker.html

<!doctype html>

<title>CodeMirror: Breakpoint Demo</title>
<meta charset="utf-8"/>
<link rel=stylesheet href="../doc/docs.css">

<link rel="stylesheet" href="../lib/codemirror.css">
<script src="../lib/codemirror.js"></script>
<script src="../mode/javascript/javascript.js"></script>
<style type="text/css">
      .breakpoints {width: .8em;}
      .breakpoint { color: #822; }
      .CodeMirror {border: 1px solid #aaa;}
    </style>
<div id=nav>
  <a href="http://codemirror.net"><h1>CodeMirror</h1><img id=logo src="../doc/logo.png"></a>

  <ul>
    <li><a href="../index.html">Home</a>
    <li><a href="../doc/manual.html">Manual</a>
    <li><a href="https://github.com/codemirror/codemirror">Code</a>
  </ul>
  <ul>
    <li><a class=active href="#">Breakpoint</a>
  </ul>
</div>

<article>
<h2>Breakpoint Demo</h2>
<form><textarea id="code" name="code">
var editor = CodeMirror.fromTextArea(document.getElementById("code"), {
  lineNumbers: true,
  gutters: ["CodeMirror-linenumbers", "breakpoints"]
});
editor.on("gutterClick", function(cm, n) {
  var info = cm.lineInfo(n);
  cm.setGutterMarker(n, "breakpoints", info.gutterMarkers ? null : makeMarker());
});

function makeMarker() {
  var marker = document.createElement("div");
  marker.style.color = "#822";
  marker.innerHTML = "●";
  return marker;
}
</textarea></form>

<p>Click the line-number gutter to add or remove 'breakpoints'.</p>

    <script>eval(document.getElementById("code").value);</script>

  </article>