Bug 212370 [Regression] Negative value can not be shown both in chart builder and when preview [13]
chart/org.eclipse.birt.chart.engine/src/org/eclipse/birt/chart/computation/withaxes/PlotWith2DAxes.java
private StackedSeriesLookup ssl = null;
	private int iMarginPercent = 0;
	private Bounds boPlotWithMargin = BoundsImpl.create( 0, 0, 100, 100 );
	/**
	 * The default constructor
	 * 
	 * @param _ids
	 *            The display server using which the chart is computed
	 * @param _cwa
	 *            An instance of the model (ChartWithAxes)
	 * @throws ValidationException
	 * @throws UndefinedValueException
	 * @throws UnexpectedInputException
	 */
	public PlotWith2DAxes( IDisplayServer _ids, ChartWithAxes _cwa,
			RunTimeContext _rtc ) throws IllegalArgumentException,
			ChartException
	{
		cwa = _cwa;
		ids = _ids;
		rtc = _rtc;
		ssl = new StackedSeriesLookup( _rtc );
		dPointToPixel = ids.getDpiResolution( ) / 72d;
		buildAxes( ); 
	}
	/**
	 * Internally maps the EMF model to internal (non-public) rendering fast
	 * data structures
	 */
	final void buildAxes( ) throws IllegalArgumentException, ChartException