Bug 122869 Drag a parameter from data explorer view into a table in library, a new parameter is created automatically.
Description:Drag a parameter from data explorer view into a table in library, a new parameter is created automatically. Steps to reproduce: 1. Add a cascading parameter and a table in a library file. 2. Drag a parameter from data explorer view into a table cell in layout editor. 3. Find that a new parameter was added in data explorer view automatically.
UI/org.eclipse.birt.report.designer.ui/src/org/eclipse/birt/report/designer/internal/ui/dialogs/ExpressionTreeSupport.java
* 
	 */
	public void addMouseTrackListener( )
	{
		Assert.isNotNull( tree );
		tree.addMouseTrackListener( new MouseTrackAdapter( ) {
			public void mouseHover( MouseEvent event )
			{
				Widget widget = event.widget;
				if ( widget == tree )
				{
					Point pt = new Point( event.x, event.y );
					TreeItem item = tree.getItem( pt );
					if ( item == null )
						tree.setToolTipText( "" );
					else
					{
						String text = (String) item.getData( ITEM_DATA_KEY_TOOLTIP );
						tree.setToolTipText( text );
					}
				}
			}
		} );
	}
	/**
	 * Add double click behaviour. Must set Tree before execution.
	 * 
	 */
	public void addMouseListener( )
	{