title: GWT - popup menu with submenus - advise some UI lib
body: <p>I am looking for some kind of GWT library which has popup menu with submenu(s) support; I mean something like <a href="http://google-web-toolkit.googlecode.com/svn/javadoc/2.0/com/google/gwt/user/client/ui/doc-files/MenuBar.png" rel="nofollow noreferrer">this</a> <strong>but with no upper menu bar</strong> because I need to have it visible on some Button click for example;</p>
  
  <p>something like this instead of the MenuBar: </p>
  
  <p><img src="https://i.stack.imgur.com/E1zCg.png" alt="enter image description here"></p>
  
  <p>So I need your practical advice where can I find a gwt library which supports that kind of component(s) ? I know it is popup menu(s) combination but I am interested to find an optimal framework solution or something which is not too heavy...</p>
  
  <p>P.S> GWT 2.3</p>
  
  <p>Thanks</p>