code: public static IVdmStackFrame getEvaluationContext(IWorkbenchWindow window)
  	{
  		List<IWorkbenchWindow> alreadyVisited = new ArrayList<IWorkbenchWindow>();
  		if (window == null)
  		{
  			window = fgManager.fActiveWindow;
  		}
  		return getEvaluationContext(window, alreadyVisited);
  	}
docs: Returns the evaluation context for the given window, or <code>null</code> if none. The evaluation context
  corresponds to the selected stack frame in the following priority order:
  <ol>
  <li>stack frame in active page of the window</li>
  <li>stack frame in another page of the window</li>
  <li>stack frame in active page of another window</li>
  <li>stack frame in a page of another window</li>
  </ol>
  
  @param window
  the window that the evaluation action was invoked from, or <code>null</code> if the current window
  should be consulted
  @return the stack frame that supplies an evaluation context, or <code>null</code> if none
  @return IJavaStackFrame