Bug 120345 Need a URL generator API from Engine
The Chart Engine needs the ability to generate a viewer URL from an ActionHandle, this can be provided by a Report Engine public API for instance. The URL should usable as is by the viewer without any additional change. The Chart Engine can take care of evaluating the expressions inside the ActionHandle before calling the Report Engine API if necessary.
engine/org.eclipse.birt.report.engine/src/org/eclipse/birt/report/engine/extension/IReportItemPresentation.java
* processes the extended item in report presentation environment.
	 * 
	 * @param rowSets
	 *            rowSets an array of row sets that is passed to the extension
	 * @return the returned value could be different depending on the type of
	 *         the output. For image, returns an input stream or byte array that
	 *         the engine could retrieve data from
	 * @throws BirtException
	 *             throws exception when there is a problem processing the
	 *             extended item
	 */
	public abstract Object onRowSets( IRowSet[] rowSets ) throws BirtException;
	/**
	 * Get the size of the extended item. The size is a Dimension object. The
	 * width and height can only be in absolute units (inch, mm, etc.) or pixel.
	 * It can not be a relative size such as 150% or 1.2em. Notice that an
	 * extended item can obtain its design-time size information by querying DE.
	 * This function is needed because the actual size may not be the same as
	 * the design-time size.
	 * 
	 * @return the size of the extended item. Return null if the size does not
	 *         matter or can not be determined.
	 */
	public Size getSize( );
	/**
	 * Performs clean up work
	 */
	public void finish( );
}