001    // Copyright 2011 The Apache Software Foundation
002    //
003    // Licensed under the Apache License, Version 2.0 (the "License");
004    // you may not use this file except in compliance with the License.
005    // You may obtain a copy of the License at
006    //
007    // http://www.apache.org/licenses/LICENSE-2.0
008    //
009    // Unless required by applicable law or agreed to in writing, software
010    // distributed under the License is distributed on an "AS IS" BASIS,
011    // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
012    // See the License for the specific language governing permissions and
013    // limitations under the License.
014    
015    package org.apache.tapestry5.tree;
016    
017    /**
018     * Tracks which <em>leaf</em> nodes of a {@link TreeModel} are currently selected. The {@linkplain DefaultTreeSelectionModel default
019     * implementation} simply stores a set of {@linkplain TreeNode#getId() unique node
020     * ids} to identify selected nodes. The selection model is updated whenever the user clicks on the label for a leaf node.
021     * <p/>
022     * In the future, new methods may be added that will support selection of folders as well as leafs, and define the rules for
023     * how selections and de-selections propagate down to children or up to parents.
024     *
025     * @param <T> type of node
026     * @see org.apache.tapestry5.corelib.components.Tree
027     * @since 5.3
028     */
029    public interface TreeSelectionModel<T>
030    {
031    
032        /**
033         * Returns {@code true}, if the given node is selected.
034         *
035         * @param node node to check
036         */
037        boolean isSelected(TreeNode<T> node);
038    
039        /**
040         * Selects a node.
041         *
042         * @param node node to select
043         */
044        void select(TreeNode<T> node);
045    
046        /**
047         * Unselects a node.
048         *
049         * @param node node to unselect
050         */
051        void unselect(TreeNode<T> node);
052    
053        /**
054         * Clears the selection.
055         */
056        void clear();
057    }