Bug 193886 NPE is thrown when preview external CSS style in ppt[1205]
engine/org.eclipse.birt.report.engine.emitter.ppt/src/org/eclipse/birt/report/engine/emitter/ppt/PPTRender.java
*/
	protected IReportContext context;
	
	protected IEmitterServices services;
	protected float scale;
	protected int hTextSpace = 70;
	protected int vTextSpace = 100;
	protected float lToP;
	
	private final Stack containerStack = new Stack( );
	
	private Map imageNames = new HashMap( );
	
	private Map imageExtensions = new HashMap( );
	
	private Map fileNamesLists = new TreeMap( );
	private List currentImageContents = new ArrayList( );
	/**
	 * Returns the output format, always is "ppt".
	 * 
	 * @return the output format
	 */
	public String getOutputFormat( )
	{
		return "ppt";
	}
	/**
	 * Initializes the PPTEmitter.
	 * 
	 * @param services