/*******************************************************************************
* Copyright (c) 2005, 2015 IBM Corporation and others.
* All rights reserved. This program and the accompanying materials
* are made available under the terms of the Eclipse Public License v1.0
* which accompanies this distribution, and is available at
* http://www.eclipse.org/legal/epl-v10.html
*
* Contributors:
* IBM Corporation - initial API and implementation
* John Cortell, Freescale - bug 289409
*******************************************************************************/
package org.eclipse.jface.viewers;
/**
* The ILazyTreeContentProvider is the content provider for tree viewers created
* using the SWT.VIRTUAL flag that only wish to return their contents as they
* are queried.
*
* @since 3.2
*/
public interface ILazyTreeContentProvider extends IContentProvider {
/**
* Called when a previously-blank item becomes visible in the TreeViewer. If
* the content provider knows the child element for the given parent at this
* index, it should respond by calling
* {@link TreeViewer#replace(Object, int, Object)}. The content provider
* should also update the child count for any replaced element by calling
* {@link TreeViewer#setChildCount(Object, int)}. If the given current child
* count is already correct, setChildCount does not have to be called since
* a call to replace will not change the child count. If the content
* provider doesn't know the child count at this point, and can more
* efficiently determine if the element has <i>any</i> children, then it can
* instead call {@link TreeViewer#setHasChildren(Object, boolean)}.
*
* <p>
* <strong>NOTE</strong> #updateElement(int index) can be used to determine
* selection values. If TableViewer#replace(Object, int) is not called
* before returning from this method, selections may have missing or stale
* elements. In this situation it is suggested that the selection is asked
* for again after replace() has been called.
*
* @param parent
* The parent of the element, or the viewer's input if the
* element to update is a root element
* @param index
* The index of the element to update in the tree
*/
public void updateElement(Object parent, int index);
/**
* Called when the TreeViewer needs an up-to-date child count for the given
* element, for example from {@link TreeViewer#refresh()} and
* {@link TreeViewer#setInput(Object)}. If the content provider knows the
* given element, it should respond by calling
* {@link TreeViewer#setChildCount(Object, int)}. If the given current
* child count is already correct, no action has to be taken by this content
* provider.
*
* @param element
* The element for which an up-to-date child count is needed, or
* the viewer's input if the number of root elements is requested
* @param currentChildCount
* The current child count for the element that needs updating
*/
public void updateChildCount(Object element, int currentChildCount);
/**
* Returns the parent for the given element, or <code>null</code>
* indicating that the parent can't be computed.
* In this case the tree-structured viewer can't expand
* a given node correctly if requested.
*
* @param element the element
* @return the parent element, or <code>null</code> if it
* has none or if the parent cannot be computed
*/
public Object getParent(Object element);
}