Bug 211773 Legend entries overlap
chart/org.eclipse.birt.chart.engine/src/org/eclipse/birt/chart/computation/LegendBuilder.java
* @return a non empty value.
	 */
	private Object getNonEmptyValue( Object value, Object defaultValue )
	{
		if ( value == null || value.toString( ).length( ) == 0 )
		{
			return defaultValue;
		}
		
		return value;
	}
	private double[] computeVerticalByTopBottomValue( IDisplayServer xs,
			Chart cm, SeriesDefinition[] seda, RunTimeContext rtc,
			ITextMetrics itm, Label la, LegendData legendData )
			throws ChartException
	{
		double dWidth = 0, dHeight = 0;
		double dW, dMaxW = 0, dColumnWidth;
		double dRealHeight = 0, dExtraWidth = 0, dDeltaHeight;
		ArrayList columnList = new ArrayList( );
		
		double dSeparatorThickness = legendData.dSeparatorThickness
				+ legendData.dVerticalSpacing;
		for ( int j = 0; j < seda.length; j++ )
		{
			List al = seda[j].getRunTimeSeries( );
			FormatSpecifier fs = seda[j].getFormatSpecifier( );
			boolean oneVisibleSerie = false;
			for ( int i = 0; i < al.size( ); i++ )
			{