gecko/toolkit/content/tests/chrome/test_popup_preventdefault.xul

<?xml version="1.0"?>
<?xml-stylesheet href="chrome://global/skin" type="text/css"?>
<?xml-stylesheet href="chrome://mochikit/content/tests/SimpleTest/test.css" type="text/css"?>

<window title="Popup Prevent Default Tests"
  onload="setTimeout(runTest, 0);"
  xmlns:html="http://www.w3.org/1999/xhtml"
  xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul">

  <title>Popup Prevent Default Tests</title>
  <script type="application/javascript" src="chrome://mochikit/content/MochiKit/packed.js"></script>
  <script type="application/javascript" src="chrome://mochikit/content/tests/SimpleTest/SimpleTest.js"></script>

<!--
  This tests checks that preventDefault can be called on a popupshowing
  event and that preventDefault has no effect for the popuphiding event.
  -->

<script>
SimpleTest.waitForExplicitFinish();

var gBlockShowing = true;
var gShownNotAllowed = true;

function runTest()
{
  document.getElementById("menu").open = true;
}

function popupShowing(event)
{
  if (gBlockShowing) {
    event.preventDefault();
    gBlockShowing = false;
    setTimeout(function() {
                 gShownNotAllowed = false;
                 document.getElementById("menu").open = true;
               }, 3000, true);
  }
}

function popupShown()
{
  ok(!gShownNotAllowed, "popupshowing preventDefault");
  document.getElementById("menu").open = false;
}

function popupHiding(event)
{
  // since this is a content test, preventDefault should have no effect
  event.preventDefault();
}

function popupHidden()
{
  ok(true, "popuphiding preventDefault not allowed");
  SimpleTest.finish();
}
</script>

<button id="menu" type="menu" label="Menu">
  <menupopup onpopupshowing="popupShowing(event);"
             onpopupshown="popupShown();"
             onpopuphiding="popupHiding(event);"
             onpopuphidden="popupHidden();">
    <menuitem label="Item"/>
  </menupopup>
</button>

<body xmlns="http://www.w3.org/1999/xhtml">
<p id="display">
</p>
<div id="content" style="display: none">
</div>
<pre id="test">
</pre>
</body>

</window>