001// Copyright 2006, 2008, 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
015package org.apache.tapestry5.runtime;
016
017import org.apache.tapestry5.ComponentResources;
018
019/**
020 * A stateful object that manages the process of rendering a page. Rending a page in Tapestry is based on a command
021 * queue.
022 */
023public interface RenderQueue
024{
025    /**
026     * Adds the new command to the front of the queue.
027     */
028    void push(RenderCommand command);
029
030    /**
031     * Indicates that a component is starting its render. A stack of active components is used for exception reporting.
032     * 
033     * @param resources
034     *            identifies the component that is rendering
035     */
036    void startComponent(ComponentResources resources);
037
038    /**
039     * Corresponds to {@link #startComponent(ComponentResources)}, used to denote when the most recently started
040     * component finishes
041     * rendering.
042     */
043    void endComponent();
044}