Bug 313297 XML data set fail in chart data preview
chart/org.eclipse.birt.chart.ui/src/org/eclipse/birt/chart/ui/swt/CustomPreviewTable.java
* String object.
	 * 
	 * @return column head object
	 * 
	 * @since 2.3
	 */
	public Object getCurrentColumnHeadObject( )
	{
		return ( iColumnIndex != -1 ) ? fHeadings.get( iColumnIndex ) : null;
	}
	
	/**
	 * Returns the index of the column that the user right-clicked on last. -1
	 * if user hasn't right-clicked in the table yet. This method is for use to
	 * determine the column for which the popup-menu is to be displayed...since
	 * the menu is handled externally.
	 * 
	 * @return the last column in which the user has right-clicked.
	 */
	public int getCurrentColumnIndex( )
	{
		return iColumnIndex;
	}
	public int getColumnNumber( )
	{
		return fHeadings.size( );
	}
	public void setColumnColor( int index, Color clr )
	{
		cnvCells.setColumnColor( index, clr );