001    // Copyright 2006 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.runtime;
016    
017    import org.apache.tapestry5.MarkupWriter;
018    
019    /**
020     * A command used during rendering of a page.
021     */
022    public interface RenderCommand
023    {
024        /**
025         * Invoked on an object to request that it render itself. This involves a mix of invoking methods on the writer, and
026         * queueing up additional commands (often, representing children of the object that was invoked) to perform
027         * additional rendering.
028         * <p/>
029         * In this way, rendering is a tail recursive algorithm, but is not implemented using tail recursion.
030         */
031        void render(MarkupWriter writer, RenderQueue queue);
032    }