where we construct that tree structure and create an observer widget for it.

\code
#include <QApplication>

#include <QtilitiesCoreGui>
using namespace QtilitiesCoreGui;

int main(int argc, char *argv[])
{
  QtilitiesApplication a(argc, argv);

  // Create a tree using TreeNode, a class inheriting Observer:
  TreeNode* rootNode = new TreeNode("Root");
  TreeNode* nodeA = rootNode->addNode("Node A");
  TreeNode* nodeB = rootNode->addNode("Node B");
  rootNode->addItem("Child 1");
  rootNode->addItem("Child 