Bug 191005 PDF preview hangs up with attached xtab.[1102]
engine/org.eclipse.birt.report.engine/src/org/eclipse/birt/report/engine/layout/pdf/PDFStackingLM.java
{
				content.setExtension( IContent.LAYOUT_EXTENSION, root );
				root = null;
			}
		}
		return success;
	}
	
	protected boolean isKeepWithNext()
	{
		return isLast && isFirst && pageBreakAfterAvoid( );
	}
	/**
	 * initialize dynamic layout information
	 * <ul>
	 * <li> create root area </li>
	 * <li> set MaxAvaHeight and MaxAvaWidth</li>
	 * <li> set OffsetX and OffsetY </li>
	 * <li> set CurrentIP and CurrentBP </li>
	 * </ul>
	 * 
	 * 
	 */
	protected abstract void initialize( );
	/**
	 * end current area if it is the last area of content, add bottom box
	 * property
	 * 
	 */
	protected abstract void closeLayout( );