Bug 151959 inappropriate screen operation
steps to reproduce: - create a report - add a grid item (3x3) - switch to Outline view - expand the grid item to see its rows and cells - select the grid item, and drag it into any of its own cell expected behavior: - is it an invalid screen operation? if it is, it should be banned actual behavior: - the grid item was disappeared surprisingly
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/core/DesignElement.java
{
		ElementRefValue templateParam = (ElementRefValue) getProperty( module,
				REF_TEMPLATE_PARAMETER_PROP );
		if ( templateParam == null )
			return null;
		return (TemplateParameterDefinition) templateParam.getElement( );
	}
	/**
	 * Returns a list of the descendents of this element. The descendents
	 * include elements that directly extend from this one, along with elements
	 * that extend from those, and so on recursively.
	 * <p>
	 * Part of: Inheritance system.
	 * 
	 * @return The list of descendents.
	 */
	public List getDescendents( )
	{
		ArrayList list = new ArrayList( );
		gatherDescendents( list );
		return list;
	}
	/**
	 * Builds up a list of the elements that extend from this one, directly or
	 * indirectly.
	 * <p>
	 * Part of: Inheritance system.
	 * 
	 * @param list
	 *            The list of descendents.