title: How to display a popup menu by mouse left click in swt?
body: <p>How to display a popup menu by mouse left click? I know the default is for mouse right click. But I want to expand(display) the menu just by a normal selection of a  button. (by normal left click). How to popup a popup menu by normal right click is as follows.</p>
  
  <pre><code>final Button btnNewgroup = new Button(compositeTextClient, SWT.NONE);
  Menu menu = new Menu(btnNewgroup);
  btnNewgroup.setMenu(menu);
  MenuItem mntmNewItem = new MenuItem(menu, SWT.NONE);
  mntmNewItem.setText("New Item");
  MenuItem mntmNewItem2 = new MenuItem(menu, SWT.NONE);
  mntmNewItem2.setText("New Item2");
  </code></pre>