Bug 214254 Expose Javascript "event" object for interactivity
When doing interactivity with a chart, and specifying a Mouse Click event with an Invoke Script action, the browser event object should be passed into the script. This object should be named "evt", and accompany the other standard category and value series parameters.
chart/org.eclipse.birt.chart.device.extension/src/org/eclipse/birt/chart/device/image/JavaxImageIOWriter.java
IIOWriteWarningListener,
		IImageMapEmitter
{
	protected Image _img = null;
	protected Object _oOutputIdentifier = null;
	private Bounds _bo = null;
	private boolean _bImageExternallySpecified = false;
	private static ILogger logger = Logger.getLogger( "org.eclipse.birt.chart.device.extension/image" ); 
	private final static String NO_OP_JAVASCRIPT = "javascript:void(0);"; 
	private final static String POLY_SHAPE = "poly"; 
	
	private Map callbackMethodsRegistry = new HashMap( 5 );
	
	/**
	 * Returns the output format string for this writer.
	 * 
	 * @return
	 */
	protected abstract String getFormat( );
	/**
	 * Returns the output image type for this writer.
	 * 
	 * @see java.awt.image.BufferedImage#TYPE_INT_RGB
	 * @see java.awt.image.BufferedImage#TYPE_INT_ARGB