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
return false;
		if ( obj == this )
			return true;
		if ( obj instanceof DesignElementHandle )
			return ( (DesignElementHandle) obj ).getElement( ) == this;
		return false;
	}
	/**
	 * Returns the slot that contains the given content element.
	 * 
	 * @param content
	 *            the element to find
	 * @return the number of the slot that contains the element, or -1 if this
	 *         element does not contain the content element.
	 */
	public int findSlotOf( DesignElement content )
	{
		if ( content == null || content.getContainer( ) != this )
			return NO_SLOT;
		return content.getContainerSlot( );
	}
	/**
	 * Checks whether the property of current element is editable.
	 * 
	 * @return <code>true</code> if the property of current element is
	 *         editable. Otherwise <code>false</code>.
	 */
	public boolean canEdit( )
	{
		return !isRootIncludedByModule( );