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
ArrayList propMasks = (ArrayList) getLocalProperty( module,
				PROPERTY_MASKS_PROP );
		if ( propMasks != null )
		{
			ListIterator masks = propMasks.listIterator( );
			while ( masks.hasNext( ) )
			{
				PropertyMask mask = (PropertyMask) masks.next( );
				errors.addAll( mask.validate( module, this ) );
			}
		}
		return errors;
	}
	/**
	 * Checks all structures in the specific property whose type is structure
	 * list property type. This method is used for element semantic check. The
	 * error is kept in the report design's error list.
	 * 
	 * @param module
	 *            the module
	 * @param propName
	 *            the name of the structure list type