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
015package org.apache.tapestry5.runtime;
016
017import org.apache.tapestry5.MarkupWriter;
018
019/**
020 * A command used during rendering of a page.
021 */
022public 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}