001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017package org.apache.wicket.markup.renderStrategy;
018
019import org.apache.wicket.Component;
020import org.apache.wicket.MarkupContainer;
021import org.apache.wicket.markup.html.internal.HtmlHeaderContainer;
022import org.apache.wicket.util.lang.Args;
023import org.apache.wicket.util.visit.IVisit;
024import org.apache.wicket.util.visit.IVisitor;
025
026/**
027 * This has been Wicket's default header render strategy before WICKET 1.5 which uses
028 * {@link MarkupContainer#visitChildren(org.apache.wicket.util.visit.IVisitor)} to traverse the hierarchy to
029 * render the children headers.
030 * 
031 * Since child contributions are added to the markup after the parent contributions, children may
032 * replace / modify existing settings. Which is not good. Instead the parent (container) should be
033 * in control (see <a href="https://issues.apache.org/jira/browse/WICKET-2693">WICKET-2693</a>).
034 * 
035 * @author Juergen Donnerstag
036 */
037public class ParentFirstHeaderRenderStrategy extends AbstractHeaderRenderStrategy
038{
039        /**
040         * Construct.
041         */
042        public ParentFirstHeaderRenderStrategy()
043        {
044        }
045
046        @Override
047        protected void renderChildHeaders(final HtmlHeaderContainer headerContainer,
048                final Component rootComponent)
049        {
050                Args.notNull(headerContainer, "headerContainer");
051                Args.notNull(rootComponent, "rootComponent");
052
053                // Only MarkupContainer can have children. Component's don't
054                if (rootComponent instanceof MarkupContainer)
055                {
056                        // Visit the children with parent first, than children
057                        ((MarkupContainer)rootComponent).visitChildren(new IVisitor<Component, Void>()
058                        {
059                                @Override
060                                public void component(final Component component, final IVisit<Void> visit)
061                                {
062                                        if (component.isVisibleInHierarchy())
063                                        {
064                                                component.internalRenderHead(headerContainer);
065                                        }
066                                        else
067                                        {
068                                                visit.dontGoDeeper();
069                                        }
070                                }
071                        });
072                }
073        }
074}