/*******************************************************************************
 * Copyright (c) 2005, 2006 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
 * Port to the D programming language:
 *     Frank Benoit <benoit@tionex.de>
 *******************************************************************************/
module dwtx.jface.viewers.ILazyTreePathContentProvider;

import dwtx.jface.viewers.IContentProvider;
import dwtx.jface.viewers.TreePath;

import dwt.dwthelper.utils;

/**
 * The ILazyTreePathContentProvider is a tree path-based content provider for
 * tree viewers created using the DWT.VIRTUAL flag that only wish to return
 * their contents as they are queried.
 *
 * @since 3.3
 */
public interface ILazyTreePathContentProvider : 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.
     *
     * <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 parentPath
     *            The tree path of parent of the element, or if the
     *            element to update is a root element, an empty tree path
     * @param index
     *            The index of the element to update in the tree
     */
    public void updateElement(TreePath parentPath, int index);

    /**
     * Called when the TreeViewer needs an up-to-date child count for the given
     * tree path, for example from {@link TreeViewer#refresh()} and
     * {@link TreeViewer#setInput(Object)}. If the content provider knows the
     * element at the given tree path, 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 treePath
     *            The tree path for which an up-to-date child count is needed, or
     *            if the number of root elements is requested, the empty tree path
     * @param currentChildCount
     *            The current child count for the element that needs updating
     */
    public void updateChildCount(TreePath treePath, int currentChildCount);

    /**
     * Called when the TreeViewer needs up-to-date information whether the node
     * at the given tree path can be expanded. If the content provider knows the
     * element at the given tree path, it should respond by calling
     * {@link TreeViewer#setHasChildren(Object, bool)}. The content provider
     * may also choose to call {@link TreeViewer#setChildCount(Object, int)}
     * instead if it knows the number of children.
     *
     * <p>
     * Intended as an optimization for when the viewer does not need the actual
     * children. Clients may be able to implement this more efficiently than
     * <code>updateChildCount</code>.
     * </p>
     *
     * @param path
     *            The tree path for which up-to-date information about children
     *            is needed
     */
    public void updateHasChildren(TreePath path);

    /**
     * Return the possible parent paths for the given element. An empty array
     * can be returned if the paths cannot be computed. In this case the
     * tree-structured viewer can't expand a given node correctly if requested.
     * If the element is a potential child of the input of the viewer, an empty
     * tree path should be an entry in the returned array.
     *
     * @param element
     *            the element
     * @return the possible parent paths for the given element
     */
    public TreePath[] getParents(Object element);
}