Looking at a modified version of the css dropdown, which can be found here:
http://www.w3schools.com/css/tryit.asp?filename=trycss_dropdown_navbar
When inserted into a dijit.layout.ContentPane, instead of floating, a scroll bar appears.
The bug has been traced back to this specific file:
<link rel="stylesheet" href="http://js.arcgis.com/3.13/dijit/themes/claro/claro.css">Despite this identification, the root cause remains elusive.
Below is the code snippet provided for reference.
<!-- File: css/dropdown.css-->
ul.dbtul {
list-style-type: none;
margin: 0;
padding: 0;
overflow: hidden;
background-color: #333;
}
li.dbtli {
float: left;
}
li.dbtli a, .dropbtn {
display: inline-block;
color: white;
text-align: center;
padding: 14px 16px;
text-decoration: none;
}
li.dbtli a:hover, .dropdown:hover .dropbtn {
background-color: red;
}
li.dropdown {
display: inline-block;
}
.dropdown-content {
display: none;
position: absolute;
background-color: #f9f9f9;
min-width: 160px;
box-shadow: 0px 8px 16px 0px rgba(0,0,0,0.2);
}
.dropdown-content a {
color: black;
padding: 12px 16px;
text-decoration: none;
display: block;
text-align: left;
}
.dropdown-content a:hover {background-color: #f1f1f1}
.dropdown:hover .dropdown-content {
display: block;
} <!DOCTYPE html>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<meta name="viewport" content="initial-scale=1, maximum-scale=1,user-scalable=no">
<link rel="stylesheet" href="http://js.arcgis.com/3.13/dijit/themes/claro/claro.css">>
<style type="text/css">
html, body { height: 100%; }
</style>
<link rel="stylesheet" type="text/css" href="css/dropdown.css"/>
<script src="//ajax.googleapis.com/ajax/libs/dojo/1.11.2/dojo/dojo.js"></script>
<script>
var dojoConfig = {
parseOnLoad: true
}
require([
'dijit/layout/BorderContainer', 'dijit/layout/ContentPane', "dojo/parser", "dojo/domReady!" ],
function(BorderContainer, ContentPane, parser) {
parser.parse();
});
</script>
</head>
<body class="claro" style="font-family: Verdana; font-size: 11px;">
<div id="mainWindow" data-dojo-type="dijit.layout.BorderContainer" data-dojo-props="design:'headline',gutters:false" style="width:100%; height:100%;">
<div data-dojo-type="dijit.layout.ContentPane" data-dojo-props="region:'top'">
<a id="linkDeRegreso" style="display:none;" href="#" class="controlesVolver"> << Volver a página anterior</a>
<div >
<ul class="dbtul">
<li class="dbtli"><a class="active" href="#home">Home</a></li>
<li class="dbtli"><a href="#news">News</a></li>
<li class="dropdown">
<a href="#" class="dropbtn">123456</a>
<div class="dropdown-content">
<a href="#">Link 1</a>
<a href="#">Link 2</a>
<a href="#">Link 3</a>
</div>
</li>
</ul>
</div>
</div>
</div>
</body>
</html>