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
{
				Object obj = columnTexts.get( rowIndex );
				if ( obj != null && obj instanceof String )
				{
					maxWidth = Math.max( gc.textExtent( (String) obj ).x,
							maxWidth );
				}
			}
			gc.dispose( );
			return maxWidth;
		}
		public void addColumn( Color clr )
		{
			Vector[] newCells = new Vector[cells.length + 1];
			Color[] newColors = new Color[colors.length + 1];
			for ( int i = 0; i < cells.length; i++ )
			{
				newCells[i] = cells[i];
				newColors[i] = colors[i];
			}
			newCells[cells.length] = new Vector( );
			newColors[colors.length] = ( clr != null ) ? clr
					: Display.getDefault( )
							.getSystemColor( SWT.COLOR_LIST_BACKGROUND );
			cells = newCells;
			colors = newColors;
			updateScrollbars( );
			super.layout( );
		}
		public void addEntry( String sText, int iColumn )